7.2 Pitched roofs

7.2 - Appendix 7.2A
	Protection from corrosion of metal components embedded in masonry
	Table 1	Anchorages, dowels and fixings
	Table 2	Protection of metal components (other than wall ties) built into masonry
7.2 - Appendix 7.2B
	Roof tile fixings
	Table 1	Recommended limits of pitch, gauge and lap for roof tiles
	Table 2	Minimum fixings for sinle lap interlocking clay and concrete tiles
	Table 3	Minimum fixings for double lap clay and concrete plain tiles
7.2 - Appendix 7.2C
	Bracing requirements for trussed rafter roofs
	Conditions and limitations on the use of standard trussed rafter bracing
7.2 - Appendix 7.2D
	Tank support details
7.2 - Appendix 7.2E
	Sizes and spacing of tile battens
7.2 - Appendix 7.2F
	Strutting for attic trusses and cut roofs that have a floor

Appendix 7.2-A

Protection from corrosion of metal components embedded in masonry

Metal components, other than wall ties built into masonry, should be made of a material listed below and protected in the way described in Table 1.

Reference should be made to Table 2 for guidance on which category of material and protection to use.

Table 1 - Anchorages, dowels and fixings

Reproduced from BS 5628 : Part 3 (with updated references) by permission of BSI.

Table 2 - Protection of metal components (other than wall ties) built into masonry

It is an NHBC recommendation that components in contact with, or embedded in, an inner leaf which is damp or exposed to periodic wettings (eg below dpc) should be protected in the same way as components in contact with, or embedded in, an outer leaf.

Reproduced from BS 5628 : Part 3 by permission of BSI.

Appendix 7.2-B

Roof tile fixings

Table 1 - Recommended limits of pitch, gauge and lap for roof tiles

Table 2 - Minimum fixings for single lap interlocking clay and concrete tiles

Notes

1. Additional nails or clips may be required depending on pitch and degree of exposure. Follow the manufacturer's recommendations. Evidence of calculations in compliance with Technical Requirements R3 and R5 may be required.
2. The mechanical fixing of all ridge and hip tiles is recommended. But in all cases ridge or hip tiles, for a distance of at least 900mm from the face of rigid masonry supports such as gables, abutments and separating walls, should be mechanically fixed.
3. Nails should be in accordance with BS 5534 and be not less than 3.35mm diameter and should penetrate at least 15mm into battens.

Table 3 - Minimum fixings for double lap clay and concrete plain tiles

Notes

1. Additional nails or clips may be required depending on pitch and degree of exposure. Follow the manufacturer's recommendations. Evidence of calculations in compliance with Technical Requirements R3 and R5 may be required.
2. The mechanical fixing of all ridge and hip tiles is recommended. But in all cases ridge or hip tiles, for a distance of at least 900mm from the face of rigid masonry supports such as gables, abutments and separating walls, should be mechanically fixed. All bonnet hip, arris hip and purpose-made hip tile fittings should be nailed.
3. Nails should be in accordance with BS 5534 and be not less than 2.65mm diameter and should penetrate at least 15mm into battens.

Appendix 7.2-C

BRACING REQUIREMENT FOR TRUSSED RAFTER ROOFS

Type of bracing	Position of bracing	Where applicable
A Diagonal rafter bracing (at approx. 45° on plan)		All trussed rafter roofs unless rigid sarking such as timber boarding or plywood is used.
B Longitudinal bracing member at ridge node point		All trussed rafter roofs
C Longitudinal binders at ceiling node points		All ceiling node points, but may be omitted where spacing between braced nodes does not exceed 3.7m
D Longitudinal bracing member at rafter node point		All rafter node points, but may be omitted where spacing between braced nodes does not exceed 4.2m
E Chevron bracing between webs		Where the span exceeds 8m. For monopitch roofs of any span and duopitch roofs over 11m span, bracing should be designed by an Engineer in accordance with Technical Requirement R5.
F Diagonal bracing to end vertical of monopitch trusses		Where not restrained by masonry wall, or cladding in plywood or similar rigid sheet material

CONDITIONS AND LIMITATIONS ON THE USE OF STANDARD TRUSSED RAFTER BRACING

1. The use of standard bracing does not apply to buildings erected on long stretches of open, level or near level country with no shelter. Examples include flat coastal fringes, fens, airfields and moorland.
   
   The height and location of the building, roof pitch and span are also important. Appendix A of BS : 5268 : Part 3 (AMD.5931) gives full details but as a general guide standard bracing is acceptable for the following situations:
   

   Roof type	Max pitch (°)	No of storeys	Maximum span (m)
   			England & Wales	Scotland		N Ireland & the Isle of Man
   Duo-pitch	35	1 2 3	10.6 9.1 8.5	9.8 7.7 7.2	(8.6) (7.2) (6.0)	9.8 7.7 7.2	(8.6) (7.2) (6.0)
   	30	1 2 3	12.0 11.5 10.2	11.6 10.0 8.8	(10.6) (8.7) (7.5)	11.6 10.0 8.8	(10.6) (8.7) (7.5)
   Mono-pitch	35	1 2 3	5.6 4.5 4.3	4.9 4.2 3.6	(4.3) (3.6) (3.0)	4.9 4.2 3.6	(4.3) (3.6) (3.0)
   	30	1 2 3	6.6 5.8 5.1	5.8 5.0 4.4	(5.1) (4.4) (3.7)	5.8 5.0 4.4	(5.1) (4.4) (3.7)
   	25	1 2 3	8.1 7.2 6.4	7.3 6.4 5.6	(6.5) (5.6) (4.5)	7.3 6.4 5.6	(6.5) (5.6) (4.5)

   Figures in brackets apply to areas of Scotland either north or west of Ullapool and to areas of Northern Ireland north of Londonderry.

2. The maximum span of the trussed rafters is 12m, the maximum height of the building is 8.4m to the underside of ceiling tie and the maximum rafter spacing is 600mm.
3. The maximum length of unsupported masonry between buttressing walls, piers or chimneys is 9m.
4. The bracing is for either duo-pitched or mono-pitched roofs.
5. The minimum size for bracing members is nominal 25mm x 100mm (3mm tolerance).
6. All bracing members to be nailed with 2 No 3.35mm diameter x 65mm long galvanized round nails to every trussed rafter they cross.
7. The trusses are supported only at their ends.
8. The roof (including hip ends) is rectangular in shape.
9. Longitudinal bracing members may be lap-jointed provided the overlap is nailed to at least two trussed rafters. They should extend the full length of the roof and tightly abut gable and party walls. Longitudinal bracing members should permit diagonal bracing to pass.
10. At least four diagonal rafter braces are required in every roof. In narrow fronted roofs and mono-pitched roofs, where braces cross, use the intersection detail 'x' above.
11. Diagonal rafter bracing should be at approximately 45° to the rafters on plan. Chevron bracing should be at approximately 45° to the web members. Diagonal bracing and chevron bracing should be across all trussed rafters, but small gaps (2 trussed rafters between sets of bracing and 1 trussed rafter adjacent to gable or separating walls) are permitted in the middle of an otherwise fully braced roof.
12. All trusses should have a plasterboard ceiling. (For trussed rafters at 600mm centres, 12.5mm plasterboard is required.) Where there is no plasterboard, such as in garages, longitudinal binder bracing (Type C above) is to be used at all ceiling node points and additional diagonal ceiling bracing is required.
13. Bracing to satisfy particular conditions shall be in addition to that detailed in the above table.
14. The ITPA Technical Handbook gives further details and advice on construction.

Appendix 7.2-D

Tank support details

Sizes for support members
Total tank capacity to marked waterline	Min. member sizes		Max. trussed rafter span for Fink configuration m	Max. bay size for other configurations m
	a and c	b
	mm
Detail A Not more than 300 L supported on four trussed rafters	47 x 72	2/35 x 97 or
		1/47 x 120	6.50	2.20
	47 x 72	2/35 x 120 or
		1/47 x 145	9.00	2.80
	47 x 72	2/35 x 145	12.00	3.80
Detail B Not more than 230 L supported on three trussed rafters	47 x 72	1/47 x 97	6.50	2.20
	47 x 72	2/35 x 97 or
		1/47 x 120	9.00	2.80
	47 x 72	2/35 x 120 or
		1/47 x 145	12.00	3.80
NOTE: Support members may be of any species with a permissible bending stress not less than that of European redwood/whitewood of GS stress grade (see 14.1).

Reproduced from BS 5268 : Part 3 by permission of BSI.

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Appendix 7.2-E

Sizes and spacing of tile battens

The sizes and spacing of tile battens should be specified from the table below.

Batten lengths should be sufficient to span over not less than three consecutive supports.

The actual batten thickness (smaller dimension) should not be less than that given in the table nor more than 3mm oversize. Actual batten width should be within ±3mm of the basic size.

BS 5534 requires delivery notes to accompany the battens and the batten to be marked with the following information - supplier, origin, "graded BS 5534", and size.

Appendix 7.2-F

Strutting for attic trusses and cut roofs that have a floor

If the distance D exceeds 2.5m between

- the node points which form the width of the floor of the attic truss or

- the supports to a floor within a cut roof,

then additional strutting should be provided as follows;

Either herringbone strutting (38mm x 38mm timber) or solid strutting not less than three-quarters the depth of the floor and at least 38mm thick should be used.