GUIDELINE

Structure – Loading and ground movement

Part D Materials and Workmanship

Part F Ventilation

Acceptable Construction Details

Acceptable Construction Details Introduction Thermal Bridging and Airtightness

Insulation in Cavity

• Diagram H ACD - 30 Ope split Lintels Ste... • Diagram H ACD - 12 Concrete Intermediate... • Diagram H ACD - 39 Concrete Forward cill... • Diagram H ACD - 38 Concrete backward cil... • Diagram H ACD - 19 Eaves Unventilated At... • Diagram H ACD - 40 Eaves Wall head close... • Diagram H ACD - 29 Flat roof parapet - I... • Diagram H ACD - 9 Insulation below groun... • Diagram H ACD - 33 Prestressed Concrete ... • Diagram H ACD - 22 Eaves Insulation betw... • Diagram H ACD - 15 Timber separating flo... • Diagram H ACD - 17 Masonry Partition Wal... • Diagram H ACD - 18 Stud partition wall -... • Diagram H ACD - 7 Insulation above groun... • Diagram H ACD - 21 Eaves Insulation betw... • Diagram H ACD - 14 Timber Intermediate f... • Diagram H ACD - 27 Gable Insulation betw... • Diagram H ACD - 26 Gable Insulation betw... • Diagram H ACD - 11 Timber suspended grou... • Diagram H ACD - 23 Eaves Insulation betw... • Diagram H ACD - 32 Ope Perforated Steel ... • Diagram H ACD - 20 Eaves Ventilated Atti... • Diagram H ACD - 34 Ope Jamb with closer ... • Diagram H ACD - 29 Flat roof Eaves - Ins... • Diagram H ACD - 8 Insulation above grou... • Diagram H ACD - 13 Concrete Intermediate... • Diagram H ACD - 28 Gable Insulation betw... • Diagram H ACD - 35 Ope Jamb with proprie... • Diagram H ACD - 36 Corner Inverted Corne... • Diagram H ACD - 16 Masonry solid and cav... • Diagram H ACD - 25 Eaves Insulation betw... • Diagram H ACD - 10 Insulation below grou... • Diagram H ACD - 37 Galvanised Top steel ...

Irish Water Requirements for Dwellings

Typical Inspection Reports

No 2. Inspection Foundations Radon Sump Barrier and Blinding No 26 Inspection of Windows on Rainwater System No 11. Inspection of Block work, Brickwork and feature stone band No 2. Inspection Foundations Radon Sump Barrier and Blinding No 12. Inspection of Block work, gable and party walls. No 28. Inspection of timber stairs installation No 3. Inspection Radon Barrier Blinding and Insulation No 22 Inspection Steel Beams and Intumescent paint No 4. Inspection of Radon Barrier and DPC No 25 Inspection of Windows on Front Elevations, DPM and Control Joint No 5. Inspection Radon Barrier Rising Walls Block and Brickwork No 17. Inspection of Stud wall construction No 8. Inspection of Blockwork and elements No 14 Inspection of Structural Beams No 23 Inspection of windows and doors being installed No 21 Inspection of Electrical first fix No 19. Inspection of Roof Construction and breathable membrane No 27 Inspection of Windows on Velux Rooflights No 10. Inspection of Joisting , bridging, Block work, Brickwork and Lintel supports No 16. Inspection of Stud wall construction. No 7. Inspection of Rising walls, Damp proof Course and Blockwork. No 18. Inspection of Roof Construction. No 7. Inspection of Chasing Block work, Brickwork and feature stone band No 6. Inspection Rising Walls Block and Brickwork No 8. Inspection of Radon Barrier and Damp proof Course. No 30 Inspection of timber stairs handrail installation No 15. Inspection of Stud wall and floor joist construction No 29. Inspection of timber stairs and handrail during construction stages No 3. Inspection Radon Barrier Blinding and Insulation No 31. Inspection of Timber stairs handrail. No 32. Inspection of Roof Access Hatch No 24 Inspection of Windows on Front and Rear Elevations No 20. Inspection of chasing in block party walls for electrical first fix No 13. Inspection Brickwork and Firestopping No 9. Inspection of Brick and Block work from 1st to 2nd floor

Structure – Loading and ground movement

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Loading and ground movement

This Technical Guidance Document is divided into two sections.

Section 1 relates to the requirements in A1 and A2.

Section 2 relates to the requirement in A3.

A1 - Loading

(1) A building shall be designed and constructed, with due regard to the theory and practice of structural engineering, so as to ensure that the combined actions that are liable to act on it are sustained and transmitted to the ground -

  • safely, and

  • without causing such deflection or deformation of any part of the building, or such movement of the ground, as will impair the stability of any part of another building.

(2) In assessing whether a building complies with sub-paragraph (1), regard shall be had to the variable actions to which it is likely to be subjected in the ordinary course of its use for the purpose for which it is intended.

A2 - Ground movement

A building shall be designed and constructed, with due regard to the theory and practice of structural engineering, so as to ensure that movements of the subsoil caused by subsidence, swelling, shrinkage or freezing will not impair the stability of any part of the building.

Other approaches

1.0.3 If other approaches are adopted, it is essential to have regard to par. 1.0.1 and to the following:

(a) The numerical values of safety factors, whether expressed explicitly or implicitly in design equations or design values, should be derived from considerations of the aspects of design and construction given in par. 1.0.1 as a whole. A change in any one of these aspects may affect the safety of the structure;

(b) Actions used in calculations should allow for possible dynamic, concentrated and peak load effects that may occur. The design should ensure that the effects of actions have been evaluated with an appropriate degree of reliability.

Definitions

1.0.4 The following definitions apply to Section 1:

Actions - Set of forces (loads) applied to the structure (direct action), or a set of imposed deformations or accelerations (indirect actions) caused for example by temperature changes or uneven settlement.

Actions are classified by their variation in time and include the following (For full definitions of all terminology relating to actions and other action types refer to I.S. EN 1990)

Permanent action (G) - Action that is likely to act throughout a given reference period and for which the variation in magnitude with time is negligible, or for which the variation is always in the indirect actions caused by e.g. shrinkage and uneven settlements etc;

Variable action (Q) - Action for which the variation in magnitude with time is neither negligible nor monotonic e.g. imposed loads on building floors, wind actions or snow loads;

Accidental action (A) - Action, usually of short duration but of significant magnitude, which is unlikely to occur on a given structure during the design working life. An accidental action e.g. due to fire, local failure, explosions or impact from vehicles, etc can be expected in many cases to cause severe consequences unless appropriate measures are taken.

Buttressing wall - A wall designed and constructed to afford lateral support to another wall perpendicular to it, support being provided from the base to the top of the wall.

Cavity width - The horizontal distance between the two leaves of a cavity wall.

Compartment wall - A wall constructed as a compartment wall to meet the requirements of Part B (Fire Safety) of the Second Schedule to the Building Regulations.

Execution - This covers all activities carried out for the physical completion of the work. The term covers work on site; it may also signify the fabrication of components off site and their subsequent erection on site.

Imposed load - Imposed loads on buildings are those arising from occupancy e.g. normal use by persons, furniture and moveable objects (e.g. moveable partitions, storage), vehicles, and anticipated rare events, such as concentrations of persons or of furniture, or the moving or stacking of objects which may occur during reorganisation or redecoration.

Pier - A member which forms an integral part of a wall, in the form of a thickened section, so as to afford lateral support to the wall to which it is bonded or securely tied.

Self weight - (included in permanent actions) includes the structure and non-structural elements including fixed services as well as the weight of earth and ballast. Non-structural elements include roofing, surfacing and coverings, partitions, suspended ceilings, wall cladding, thermal insulation, fixed services e.g. electrical, plumbing, heating, ventilating, air conditioning etc.

Separating wall - A wall or part of a wall which is common to adjoining buildings and constructed to meet the requirements of Part B (Fire Safety) of the Second Schedule to the Building Regulations.

Spacing - The distance between the longitudinal centres of any two adjacent members of the same type, measured in the plane of floor, ceiling, roof, or other part of the structure of which members form a part.

Span - The distance measured along the centre line of a member between the centres of any two adjacent bearings or supports.

Supported wall - A wall to which lateral support is afforded by a combination of buttressing walls, piers or chimneys acting in conjunction with floor(s) or roof.

Sub Section 1

Part 1 - Basic requirements for stability

1.1.1.1 This Part must be used in conjunction with Parts 2 and 3 of this sub-section.

1.1.1.2 Trussed rafter roofs should be braced in accordance with the recommendations of I.S. 193. Where, due to its form of construction, a traditionally framed roof (i.e. using rafters, purlins and ceiling joists) does not have sufficient built-in resistance to instability, for example from hipped returns, then bracing is required.

1.1.1.3 If the roof structure is braced as described above and adequately anchored to the structure beneath and the walls are designed and restrained in accordance with the requirements of Part 3 of this sub-section, no special provision should be needed to take account of loads due to the effect of wind pressure or suction. However, par. 1.1.3.26 gives details of situations in which additional ties may be required.

Part 2 - Sizes of certain timber floor, ceiling and roof members in houses

Application

1.1.2.1 This Part applies only to houses (Category A1 buildings as defined in I.S. EN 1991-1-1) with not more than two floors including the ground floor.

The use of this Part

1.1.2.2 This Part must be used in conjunction with Part 1 of this sub-section.

1.1.2.3 The guidance given in this Part assumes that:

a. the permanent and variable actions to be sustained by the floor, ceiling or roof of which the member forms part do not exceed the values given in Table 1 for a Category A1 building;

b. the species of timber and grade combinations for allocation to strength classes are those given in I.S. EN 1912;

c. the strength and stiffness properties and density strength class is in accordance with I.S. EN 338, and

d. floor boarding complying with BS 1297: 1987 is used.

1.1.2.4 Target sizes and permissible deviations should be in accordance with I.S. EN 336.

1.1.2.5 Notches and holes in simply supported floor and roof joists should be within the following limits:

a. notches should be no deeper than 0.125 times the depth of a joist and should not be cut closer to the support than 0.07 times the span, nor further away than 0.25 times the span,

b. holes should be no greater diameter than 0.25 times the depth of the joist, should be drilled at the neutral axis, should be not less than three diameters (centre to centre) apart and should be located between 0.25 and 0.4 times the span from the support, and

c. the horizontal distance between any hole and any notch should not be less than the depth of the joist.

1.1.2.6 Bearing areas and workmanship should comply with the relevant requirements of I.S. EN 1995-1-1. Refer also to par 1.1.3.22 to 1.1.3.25 of this document.

1.1.2.7 Timber joists, rafters and purlins should be designed in accordance with I.S. EN 1995-1-1 for the loadings (actions) calculated in accordance with the appropriate Eurocode.

Part 3 - Thickness of masonry walls in houses with not more than two floors including the ground floor

Application

1.1.3.1 This Part applies to houses (Category A1 buildings as defined in I.S. EN 1991-1-1) with not more than two floors including the ground floor, with walls of traditional masonry construction, with timber upper floors and with roofs covered with normal lightweight covering including clay or concrete pantiles. It also applies to domestic garages and other annexes attached to such houses.

For the design of timber frame dwellings refer to I.S. 440.

The use of this Part

1.1.3.2 This Part must be used in conjunction with Part 1 of this sub-section. All appropriate design conditions given in this part must be satisfied. Walls should comply with the relevant requirements of I.S. EN 1996-2 and additional guidance given in prS.R. 325. The wall types given in par. 1.1.3.3 may be constructed as described in par. 1.1.3.4 using the materials described in par. 1.1.3.5 and subject to the requirements of pars. 1.1.3.6 to 1.1.3.27.

Wall types

1.1.3.3 This Part applies to external walls and internal walls (including compartment walls and separating walls).

Wall construction

1.1.3.4 General wall thicknesses may be determined according to this section.

External walls

(a) Cavity walls constructed using two leaves composed of either, solid concrete blocks or bricks of not less than 100 mm thickness, or of clay bricks, tied together with wall ties appropriate to the width of cavity. The inner leaf may be constructed using minimum 100 mm thick lightweight solid concrete blocks;

(b) Cavity block walls constructed using 215 mm hollow concrete blocks.

Internal load bearing walls

(a) Internal load bearing walls composed of solid or lightweight solid concrete blocks or bricks;

(b) Separating walls composed of 215 mm thick solid concrete blocks (refer to Technical Guidance Document E for guidance on sound insulation);

(c) Separating walls of cavity construction composed of two leaves of solid concrete blocks of not less than 100 mm thickness (refer to Technical Guidance Document E for guidance on sound insulation).

Materials

1.1.3.5 Walls should be properly bonded and solidly put together with mortar and comply with the relevant requirements of I.S. EN 1996-2 and additional guidance given in prS.R. 325. The materials used should meet the following minimum designations, strengths and other qualities.

Solid concrete blocks

Solid concrete blocks should have a thickness as required by par 1.1.3.4 and be Group 1 masonry units conforming to I.S. EN 771-3. The declared mean compressive strength for Group 1(see note 1) masonry units should be 7.5N/mm² (dry strength to I.S. EN 772-1);

Lightweight solid concrete blocks

Lightweight solid concrete blocks should have a thickness as required by par 1.1.3.4 and be Group 1 masonry units conforming to I.S. EN 771-3.

The declared mean compressive strength for Group 1 masonry units should be 7.5N/mm² (dry strength to I.S. EN 772-1);

Hollow concrete blocks
Hollow concrete blocks should have a thickness as required by par 1.1.3.4 and be Group 2(see note 2) masonry units conforming to I.S. EN 771-3. The declared mean compressive strength for Group 2 masonry units to this standard should be 4.5N/mm² (dry strength to I.S. EN 772-1);

Note 1: Group 1 masonry units have not more than 25% formed voids (20% for frogged bricks).

Note 2: Group 2 masonry units have formed voids greater than 25%, but not more than 55%.

Clay bricks

Clay bricks should have a thickness of 103 mm, be frost resistant and conform to I.S. EN 771-1 and may be either Group 1 or Group 2 masonry units. The declared mean compressive strength for Group 1 masonry units should be 9N/mm² and 13 N/mm² for Group 2 masonry units;

Other masonry units

Other masonry units should have strength and thickness equivalent to those listed above and should conform to the following standards.

  • Calcium silicate masonry units conforming to I.S. EN 771-2;

  • Autoclaved aerated concrete masonry units conforming to I.S. EN 771-4;

  • Manufactured stone masonry units conforming to I.S. EN 771-5;

  • Natural stone masonry units conforming to I.S. EN 771-6.

Lintels

Lintels should be designed for the actions and spans occurring where they are employed and should be installed strictly in accordance with the manufacturers' instructions. Prefabricated lintels should comply with I.S. EN 845-2 and additional guidance given in prS.R. 325.

Mortar

Mortar should be:

(a)

(i) mortar designation (iii) according to I.S. EN 1996-1-1;

(ii) strength class M4 according to I.S. EN 998-2 (nominally a 1:1:5 or 6 mixture of CEM I, lime and fine aggregate measured by volume of dry materials), or

(b) of equivalent or greater strength and durability to the specification in (a) above.

Wall ties

Wall ties should comply with I.S. EN 845-1 and should be material references 1 or 3 in I.S. EN 845 Table A1 austenitic stainless steel. Wall ties should be selected in accordance with Table NA.1 of I.S. EN 845-1.

Maximum loads

Vertical actions

1.1.3.6 The design considerations given in this section are intended to be adequate for the vertical actions given in the table below.

Table HA1 - Design actions - Extract from TGD A
Table HA1 - Design actions - Extract from TGD A

Part 3 - 1.1.3.7 Maximum height of buildings

Maximum height of buildings

1.1.3.7 The design guidance in this section is based on I.S. EN1991-1-4. The maximum allowable height of a building (to ridge level) within the scope of Part 3 may be derived using the procedure set out in Diagram 1. The values given in Table 4 correlate to various site exposure conditions and wind speeds. A map showing wind speeds is given in Figure 1a of Diagram 1.

Where more exposed terrain is involved or where there is reason to believe that higher wind speeds may pertain e.g. due to funneling effects etc. a separate design check in accordance with I.S. EN 1991-1-4 should be carried out. Part 3 of this Technical Guidance Document is not applicable if the site peak velocity pressure determined in this manner exceeds 1.2 kN/m2.

Diagram HA1 - Maximum height of buildings  - Extract from TGD A
Diagram HA1 - Maximum height of buildings - Extract from TGD A

Diagram HA1b - Maximum height of buildings  - Extract from TGD A
Diagram HA1b - Maximum height of buildings - Extract from TGD A

Table HA2 - Factor O - Extract from TGD A
Table HA2 - Factor O - Extract from TGD A

Table HA3 - Factor A - Extract from TGD A
Table HA3 - Factor A - Extract from TGD A

Table HA4 - Maximum allowable building height in metres to ridge level - Extract from TGD A
Table HA4 - Maximum allowable building height in metres to ridge level - Extract from TGD A

Part 3 Retained earth

Retained earth

1.1.3.8 Differences in level of ground or other solid construction between one side of the wall and the other must be less than four times the thickness of the wall.

Diagram HA2 -  Size and proportion of buildings - Extract from TGD A
*Diagram HA2 - Size and proportion of buildings - Extract from TGD A *

Limitations on building geometry

1.1.3.9 Residential buildings (see Diagram 2)

(a) No part of any wall or roof should be more than 10 m above the lowest adjacent ground level.

(b) The width of the building should not be less than half the height of the building.

(c) The width of a wing should not be less than half the height of the wing when the projection P exceeds twice the width W2.

1.1.3.10 Floors should be as described below:

(a) Ground floors - Timber floors or ground supported concrete floors or suspended concrete floors of maximum span 5 m.

(b) Upper floors - Traditional timber floor of maximum span 5 m.

1.1.3.11 The floor to floor and ceiling to ceiling heights should not exceed 2.7 m.

1.1.3.12 The roof span should not exceed 12 m.

Lateral support and end restraint

1.1.3.13 The ends of every load-bearing wall should be bonded or otherwise securely tied throughout their full height to a buttressing wall pier or chimney. The maximum length of wall between vertical supports should not exceed 9 m. Longer walls should be provided with intermediate support, dividing the wall into distinct lengths, by buttressing walls, piers or chimneys, which provide support throughout the full height of the wall.

Buttressing

1.1.3.14 The thickness of the buttressing should not be less than 100 mm. Diagram 3 gives details of the limiting dimensions of openings and recesses in walls, including buttressing walls.

Diagram HA3  - Sizes of openings and recesses- Extract from TGD A

Diagram HA3 - Sizes of openings and recesses- Extract from TGD A

1.1.3.15 Piers in solid walls should be not less than 190 mm in width and not less than 490 mm thick. Piers in hollow block walls should be not less than 190 mm in width and not less than 590 mm thick. Chimneys should be not less than 490 mm thick and be composed of units not less than 100 mm thick (see Diagram 4).

Diagram HA4 - Piers and chimneys Extract from TGD A

Diagram HA4 - Piers and chimneys Extract from TGD A

1.1.3.16 Internal buttressing to walls in upper floors may be provided by stud partitions not less than 1200 mm long constructed from 35 mm x 75 mm kiln dried timber with studs at not more than 400 mm centres and two rows of noggings. The end stud of the partition should be fixed to the wall using drilled screw fixings at the top and at each of the noggings. Reference should be made to Part L - Conservation of Fuel and Energy for guidance on limiting thermal bridging.

1.1.3.17 Notwithstanding the rules in pars. 1.1.3.13 to 1.1.3.16, a supported wall may contain an unbuttressed section adjoining an opening as shown in Diagram 5 where -

a. the opening is in the ground storey of an external buttressing wall;

b. the opening does not exceed 2.4 m in height;

c. the supported wall is restrained at first floor level or, where the building is a single storey building, at roof level;

d. the supported wall is properly bonded to the buttressing wall below the ground floor level;

e. the supported wall is bonded to the buttressing wall above the opening by a beam or lintel spanning the opening in the buttressing wall;

f. the buttressing wall is properly bonded to a storey height wall, pier or chimney at the opposite side of the opening to the supported wall;

g. the supported wall is properly bonded to a storey height wall not more than 5.5 m from its unbuttressed section;

h. the beam or lintel described in (e) above is provided at each end with a bearing length of 400 mm or is supported on a padstone having a length of 400 mm.

Diagram HA5  - Unbuttressed wall sections - Extract from TGD A

Diagram HA5 - Unbuttressed wall sections - Extract from TGD A

Diagram HA5b - Unbuttressed wall sections Extract from TGD A

Diagram HA5b - Unbuttressed wall sections Extract from TGD A

Part 3 Openings and chases in walls

1.1.3.18 The number, size and position of openings should not impair the stability of a wall or the lateral support provided by a buttressing wall to a supported wall. Construction over openings and recesses should be adequately supported and the ends of lintels and beams should be provided with adequate bearing. All window and door lintels should have a minimum bearing length of 150 mm. In certain circumstances e.g. beam bearings, it may be necessary to provide padstones or longer bearings.

1.1.3.19 The maximum length of an opening or thickness-reducing recess in any wall should not exceed 3 m. Other dimensional criteria are given in Diagram 3 (see also par. 1.1.3.21).

1.1.3.20 Openings and thickness-reducing recesses in walls should not exceed 2.4 m in height (see also par. 1.1.3.21).

1.1.3.21 Dimensional criteria for chases

1) Chases should not impair the stability of the wall. Chases are not allowed when using hollow blocks.

2) Vertical chases formed after construction of masonry should not be deeper than 30 mm.

3) Horizontal or inclined chases should comply with the National Annex to I.S. EN 1996-1-1.

Further guidance on the maximum allowable widths of chases is given in the National Annex to I.S. EN 1996-1-1.

Interaction of elements

1.1.3.22 A wall in each storey of a building should extend to the full height of that storey and have horizontal lateral supports to restrict movement at right angles to its plane.

1.1.3.23 Floors and roofs should:

(a) act to transfer lateral forces from walls to buttressing walls, piers or chimneys, and

(b) be secured to the supported wall by connections specified in pars. 1.1.3.24 and 1.1.3.25.

1.1.3.24 Walls should be strapped to floors at first floor level at intervals not exceeding 2000 mm as shown in Diagram 6 (a) and (b) by 30mm x 5 mm galvanised mild steel or stainless steel tension straps which have a minimum 30 mm x 5 mm section conforming to I.S. EN 845-1. For corrosion resistance purposes, the tension straps should be material reference 14, 16.1 or 16.2 (galvanised steel) or other more resistant specifications including reference 1 or 3 (austenitic stainless steel). The declared tensile strength of tension straps should not be less than 8kN.

Straps need not be provided -

a. in the longitudinal direction of joists, if the joists are at not more than 800 mm centres and have at least

  • 90 mm bearing on the supported walls, or

  • 75 mm bearing on a timber wall plate at each end,

b. in the longitudinal direction of joists where the joists are carried on the supported wall by joist hangers in accordance with I.S. EN 845-1 of the restraint type shown in Diagram 6 (c), at not more than 800 mm centres,

c. where floors are at or about the same level on each side of a supported wall as shown in Diagram 6 (d) and contact between floors and wall is either continuous or at intervals not exceeding 2000 mm. Where contact is intermittent, the point of contact should be in line or nearly in line on plan.

Diagram HA6 - Lateral support by floors  - Extract from TGD A

Diagram HA6 - Lateral support by floors - Extract from TGD A

1.1.3.25 Gable walls should be strapped to roofs as shown in Diagrams 7 (a) and (b) by 30 x 5 mm tension straps as described in 1.1.3.24. Vertical strapping at least 1000 mm in length should be provided at eaves level at intervals not exceeding 2000 mm as shown in Diagram 7 (c).

Additional vertical straps may be necessary in the following conditions and a separate design check should be carried out to calculate uplift in accordance with I.S. EN 1991-1-4. These conditions include where:

a. The roof has a pitch of less than 15º, and/or

b. With reference to Figure 1a of Diagram 1 the site wind speed is greater than 26 m/s, and/or

c. The building is located in exposed terrain and there is reason to believe that higher wind speeds may pertain.

1.1.3.26 Where an opening in a floor or roof, such as that required for a stairway (Diagram 8), adjoins a supported wall and interrupts the continuity of lateral support, the following conditions should be satisfied:

a. the length of opening should not exceed 3000 mm measured parallel to the supported wall;

b. where a connection is provided by means other than by anchor, this should be provided throughout the length of each portion of the wall situated on each side of the opening;

c. where connection is provided by mild steel or stainless steel anchors or by packs, these should be spaced closer than 2000 mm on each side of the opening to provide the same number as if there were no opening, and

d. there should be no other interruption of lateral support.

1.1.3.27 Wall ties should be provided in cavity walls and should comply with I.S. EN 845-1 and should be material references 1 or 3 in I.S. EN 845 Table A1 austenitic stainless steel. The minimum quantity of ties provided should be:

  • 2.5 wall ties per square metre for cavity widths between 50mm and 75 mm;

  • 3 wall ties per square metre for cavity widths between 75 mm and 100 mm, and

  • 4.9 wall ties per square metre for cavity widths between of 100mm and 150 mm.

Extra wall ties are required at the jambs of openings and movement joints as shown in Diagram 9 (for use of ties in other cavity widths, see pr S.R. 325).

Diagram HA7 - Lateral support at roof level - Extract from TGD A
Diagram HA7 - Lateral support at roof level - Extract from TGD A

Diagram HA8 - Interruption of lateral support - Extract from TGD A

Diagram HA8 - Interruption of lateral support - Extract from TGD A

Diagram HA9 - Spacing of wall ties - Extract from TGD A

Diagram HA9 - Spacing of wall ties - Extract from TGD A

Part 4 - Proportions for masonry chimneys above the roof surface

Height to width relationship

1.1.4.1 Where a chimney is not supported by adequate ties or otherwise made secure, its height (H), measured from the level of the highest point of intersection with the roof surface, gutter or other part of the building and including any flue pot or terminal, should not be greater than X multiplied by W, provided that the density of the masonry is greater than 1800 kg/m3.

With reference to Diagram 1, Figure 1a):

X = 4.0 where the site wind speed is less than 26 m/s;

X = 3.5 where the site wind speed is greater than 26m/s.

W is the lesser horizontal dimension of the chimney measured at the same point of intersection (see Diagram 10).

The proportions given above are intended for general application and are valid when the associated building height to ridge level is not greater than that calculated by the procedure in Diagram 1. However, more slender chimneys may be built if they can be shown by calculation to be stable in the particular wind environment of the building.

Diagram HA10 - Proportions for masonry chimneys - Extract from TGD A

Diagram HA10 - Proportions for masonry chimneys - Extract from TGD A

Part 5 - Strip foundations of plain concrete

Conditions relating to the subsoil

1.1.5.1 There should not be -

a. made ground or wide variation in type of subsoil within the loaded area, or

b. weaker type of soil at such a depth below the soil on which the foundation rests as could impair the stability of the structure.

Design provisions

1.1.5.2 The following design provisions relate to foundations -

a. the foundations should be situated centrally under the wall;

b. strip foundations should have minimum widths in accordance with par. 1.1.5.3;

c. concrete should incorporate a cement to I.S. EN 197-1 and fine and coarse aggregate conforming to I.S. EN 12620:2002 + S.R. 16:2004 and be one of the following grades -

  • in accordance with Table NA.5 of I.S. EN 206-1:2002 for reinforced foundations, or

  • Class C12/15 (characteristic 28 day strength of 15 N/mm2) with minimum cement content 200 kg/m3 and maximum water cement ratio 0.85for plain concrete un-reinforced foundations in non-aggressive ground conditions (when volumetric mixing is required for small projects, a 1:7 cement/ aggregate mix may be used),

d. minimum thickness T of concrete foundation should be 200 mm or P, whichever is the greater, where P is derived using Table 5 (see Diagram 11);

e. foundations stepped on elevation should overlap by:

  • twice the height of the step, or

  • the thickness of the foundation, or

  • 300 mm,

whichever is greatest (see Diagram 12);

f. steps in foundations should not be of greater height than twice the thickness of the foundation and should course with walling material (see Diagram 12);

g. foundations for piers, buttresses and chimneys should project as indicated in Diagram 13, and the projection X should never be less than P.

Diagram HA11 - Foundation dimensions - Extract from TGD A

Diagram HA11 - Foundation dimensions - Extract from TGD A

Diagram HA12 - Elevation of stepped foundation - Extract from TGD A

Diagram HA12 - Elevation of stepped foundation - Extract from TGD A

Diagram HA13 - Piers and chimneys - Extract from TGD A

Diagram HA13 - Piers and chimneys - Extract from TGD A

Minimum width of strip foundations

1.1.5.3 Providing the previous conditions relating to the subsoil (par. 1.1.5.1) and design provisions relating to the foundations (par. 1.1.5.2) are observed and the type and condition of subsoil is known and loading at the base of the wall is within acceptable limits, the recommended widths of foundations given in Table 5 may be used.

Table HA5 - Minimum width of strip foundations - Extract from TGD A

Table HA5 - Minimum width of strip foundations - Extract from TGD A

Sub Section 2

Introduction

1.2.1 The following codes, standards and references are appropriate for all buildings and may be used to meet Requirements A1 and A2 provided that:

a. the design and construction of a structure is in accordance with the relevant recommendations of the codes, standards and references, and

b. where alternative codes and standards have been listed, the whole of the design for the same material should normally be based on one of the codes only.

Codes and standards

Any reference to the Eurocodes must be taken to include reference to the relevant Irish National Annex.

Loading

Eurocode Basis of structural design
I.S. EN 1990: 2002

Eurocode 1: Actions on Structures
I.S. EN 1991-1-1: 2002
I.S. EN 1991-1-3: 2003
I.S. EN 1991-1-4: 2005
I.S. EN 1991-1-5: 2003
I.S. EN 1991-1-6: 2005
I.S. EN 1991-1-7: 2006
I.S. EN 1991-3: 2006

Structural work of reinforced, pre-stressed or plain concrete

Eurocode 2: Design of Concrete Structures
I.S. EN 1992-1-1: 2005
I.S. EN 1992-3: 2006

Execution standards
I.S. EN 13670: 2009

Structural work of steel

Eurocode 3: Design of Steel Structures
I.S. EN 1993-1-1: 2005
I.S. EN 1993-1-3: 2006
I.S. EN 1993-1-4: 2006
I.S. EN 1993-1-5: 2006
I.S. EN 1993-1-6: 2007
I.S. EN 1993-1-7: 2007
I.S. EN 1993-1-8: 2005
I.S. EN 1993-1-9: 2005
I.S. EN 1993-1-10: 2005
I.S. EN 1993-1-11: 2006
I.S. EN 1993-1-12: 2007
I.S. EN 1993-5: 2007
EN 1993-6: 2007

Execution standards
I.S. EN 1090-1:2009
I.S. EN 1090-2:2008+A1: 2011

Structural work of composite steel and concrete construction

Eurocode 4: Design of Composite Concrete and Steel Structures
I.S. EN 1994-1-1: 2005

Execution standards
I.S. EN 13670: 2009
I.S. EN 1090-1: 2009
I.S. EN 1090-2: 2008+A1:2011

Structural work of timber

Eurocode 5: Design of Timber Structures
I.S. EN 1995-1-1: 2005

I.S. 440: 2009 (under revision)

Structural work of masonry

Eurocode 6: Design of Masonry Structures
I.S. EN 1996-1-1: 2005
I.S. EN 1996-2: 2006
I.S. EN 1996-3: 2006

prS.R. 325:yyyy (to be published by NSAI)

Foundations - General

Eurocode 7: Geotechnical Design
I.S. EN 1997-1: 2005
I.S. EN 1997-2: 2007

Execution standards
I.S. EN 1536: 2010
I.S. EN 1537: 2000
I.S. EN 1538: 2010
I.S. EN 12063: 1999
I.S. EN 12699:2000
I.S. EN 12715: 2000
I.S. EN 12716: 2001
I.S. EN 14199: 2005
I.S. EN 15237: 2007
I.S. EN 14679: 2005
I.S. EN 14731: 2005
I.S. EN 14475: 2006
I.S. EN 14490: 2010

Structural work of aluminium

Eurocode 9: Design of Aluminium Structures
I.S. EN 1999-1-1: 2007
I.S. EN 1999-1-3: 2007
I.S. EN 1999-1-4: 2007
I.S. EN 1999-1-5: 2007

Execution standards
I.S. EN 1090-1: 2009
I.S. EN 1090-3: 2008

Structural work of glass

BS 6262: 1982
BS 6262-1:2005
BS 6262-2:2005
BS 6262-3:2005
BS 6262-4: 2005
BS 6262-5: 2005
BS 6262-6: 2005
BS 6262-7: 2005

Appraisal of existing buildings

Appraisal of existing structures 3rd edition Institution of Structural Engineers 2010.

Building Research Establishment Digest 366: Structural appraisal of existing buildings for change of use 1991.

Structural renovation of traditional buildings, Report 111. Construction Industry Research and Information Association (1994 reprint with amendments).

Diagram HA14 - Basic snow load at 100 m above ordnance datum (extract from NA to I.S. EN 1991-1-3) - Extract from TGD A

Diagram HA14 - Basic snow load at 100 m above ordnance datum (extract from NA to I.S. EN 1991-1-3) - Extract from TGD A

Sub Section 3

Recovering of existing roof structures

1.3.1 Where new roof coverings would impose higher loads on the roof structure or where the new material would be lighter than the original material, strengthening measures may be required. The following procedure is recommended:

a. arrange for a thorough structural survey of the existing roof structure and the vertical restraints;

b. check the dry mass per unit area of the proposed roof covering and compare it with that of the existing roof covering;

c. make allowance for the increase in load due to water absorption, e.g. 0.3% for oven dry slates and up to 10.5% for clay plain tiles and concrete tiles;

d. check if the roof structure is capable of sustaining the increased load or if the vertical restraints provided for the roof structure are adequate for the wind uplift (the nett uplift may increase due to the use of lighter roofing material and/or provision of new underlay);

e. provide appropriate strengthening measures such as:

  • replacement of defective members and vertical restraints;

  • additional structural members such as trusses, rafters, bracings, purlins, etc. which are required to sustain increased loading;

  • restraining straps, additional ties and fixings to the walls to resist wind uplift.

Structural safety of external wall cladding

1.3.2 The remainder of this sub-section includes guidance for the design and construction of external wall cladding. Wall cladding presents a hazard if it becomes detached from the building. For the purposes of this section, cladding is deemed to include glazed curtain walling but not windows.

1.3.3 These provisions are not intended to provide guidance concerning the weather resistance of wall cladding which is included in Technical Guidance Document C, Site Preparation and Resistance to Moisture, or guidance on resistance to fire which is included in Technical Guidance Document B, Fire Safety.

1.3.4 Wall cladding should be capable of safely sustaining and transmitting to the supporting structure of the building all the actions which are liable to act on it.

1.3.5 Wall cladding should be securely fixed to and supported by the supporting structure of the building. The method used to secure the cladding to the structure should comprise both vertical support and horizontal restraint.

1.3.6 Provision should be made, where necessary, to accommodate differential movement of the cladding and the supporting structure of the building.

1.3.7 The cladding and its fixings including any support components should be of durable materials and the anticipated life of the fixings should not be less than that of the cladding. Where the fixings are not readily accessible for inspection and maintenance, particular care will be required in the choice of materials and standard of workmanship to be achieved (see Technical Guidance Document D). Fixings should be corrosion resistant and of a material type which is appropriate for the local environment.

Technical approach

Loading

1.3.8 Wind actions on the wall cladding should be derived from I.S. EN 1991-1-4. Due consideration should be given to local increases in wind suction arising from funnelling of wind through gaps between buildings. Forces imposed on wall cladding by ladders or access cradles for the purpose of maintenance should be derived from a consideration ofthe equipment likely to be used.

1.3.9 Where the wall cladding is required to support other fixtures such as handrails, or fittings such as antennae, signboards, etc., full account should be taken of the actions arising from such fixtures and fittings.

1.3.10 Where the wall cladding is required to function as pedestrian guarding to a stairway, ramp, vertical drop of 600 mm or greater or as a vehicle barrier, then account should be taken of the additional imposed loading, as stipulated in Technical Guidance Document K, Stairways,Ladders, Ramps and Guards.

1.3.11 Where the wall cladding is required to resist the horizontal loading from crowds, an appropriate recommended loading is given in I.S. EN 1991-1-1.

Fixings

1.3.12 The selection of fixings for securing cladding should be determined from consideration of the proven performance of the fixing and the risks associated with the particular application.

Designers should have particular regard for the following legislation and amendments thereto: Safety, Health and Welfare at Work(Construction) Regulations 2006 (S.I. No. 504 of 2006), relevant provisions of the Safety, Health and Welfare at Work Act 2005 (No. 10 of 2005) and the Safety, Health and Welfare at Work (General Application)Regulations 2007 (S.I. No. 299 of 2007).

The publication titled 'Code of practice for the design and installation of anchors - Health and Safety Authority 2010' provides practical guidance on the procedures for safe design and installation of anchors in accordance with the above legislation.

1.3.13 For design purposes, the strength of a fixing should be derived from tests using materials representative of the base material of the structure into which the fixing is to be anchored. Account should also be taken of any inherent weaknesses in the base material of the structure which may affect the design strength and durability of the fixing, e.g. cracks due to shrinkage or flexure, or voids in masonry construction.

Further guidance on fixings

1.3.14 Additional guidance on fixings is given in the following documents:

ETAG 001 Edition 1997 - Guidelines for European Technical Approval of Metal Anchors for use in Concrete - Amended November 2006, European Organisation for Technical Approvals (EOTA) http://www.eota.be

ETAG 029 Edition 2010 Guideline for European Technical Approval of metal injection anchors for use in masonry, European Organisation for Technical Approvals (EOTA) http://www.eota.be

BS 5080-1:1994

BS 5080-2:1986

BS 5427-1: 1996

1.3.15 Movement - Guidance is given in BS 8200: 1985 and prS.R. 325 on the means of providing for the differential movement between the wall cladding and the supporting structure of the building.

Codes and standards

1.3.16 The following Codes and Standards may be used in designing wall cladding:

General

BS 8200: 1985
The Institution of Structural Engineers' Report on 'Aspects of Cladding' dated 1995

Loading

I.S. EN 1990: 2002
I.S. EN 1991-1-1: 2002
I.S. EN 1991-1-4: 2005

Stone and concrete cladding

I.S. EN 1992-1-1: 2005
BS 8297: 2000
BS 8298-1: 2010
BS 8298-2: 2010
BS 8298-3: 2010
BS 8298-4: 2010
BS 8298-5: (In preparation)

Masonry cladding

prS.R. 325: yyyy (to be published by NSAI)
I.S. EN 1996-1-1: 2005
I.S. EN 1996-2: 2006
I.S. EN 1996-3: 2006

Steel cladding

I.S. EN 1993-1-1: 2005
I.S. EN 1993-1-3: 2006
I.S. EN 1993-1-5: 2006
I.S. EN 1993-1-6: 2007
I.S. EN 1993-1-8: 2005
I.S. EN 1993-1-10: 2005

Aluminium cladding

I.S. EN 1999-1-1: 2007
I.S. EN 1999-1-3: 2007
I.S. EN 1999-1-4: 2007

Timber cladding

I.S. EN 1995-1-1: 2005
I.S. 440:2009 (under revision)
External Timber Cladding 2nd Edition 2007, TRADA

Profiled sheet cladding

BS 5427-1: 1996

Glass cladding

BS 5516-1:2004
BS 5516-2:2004

Note: The use of large panels of glass in cladding of walls and roofs where the cladding is not divided into small areas by load-bearing framing requires special consideration. Guidance is given in the following document:

The Institution of Structural Engineers' Report on 'Structural use of glass in buildings' dated 1999

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