Material Specifications

Tiles and fittings

Plain clay tiles and fittings should comply with BS EN 1304. It should be noted that hand made tiles and second hand tiles, which may not comply with the dimensional requirements of BS EN 1304, may be used for vertical tiling.

Accessories

Accessories, e.g., ventilation tiles, proprietary soakers, outlets, edge trims, proprietary flashings etc., should have third party approval for the design, installation and performance.

Lead

Where lead is exposed to weathering it should be code 4 BS 1178 as a minimum and where it is protected it may be code 3. Surfaces of all exposed lead should be treated with patination oil to prevent lead oxide staining of the tiles.

Mortar

Where mortar is used as a filler a mix of 1 part cement to 4 parts sand would be satisfactory, but,where the mortar is used to fix tiles, hips and ridges, a mix of 1 part cement to 3 parts sand should be used. Most sands conforming to BS 1200 are suitable. However, a test method for measuring the tensile bond strength of the mortar is given in BS 5534.  Specific lime mortars may be required for listed buildings.

Adhesives

Where adhesives are used the adhesive manufacturer’s recommendations for the material with clay tiles should be followed.

Underlays

Fully supported -This includes roofing underlays laid directly onto the boarding or sarking. The roofing underlay should be of adequate strength, water resistance and durability with water vapour transmission high enough to prevent the formation of condensation beneath the underlay. A test carried out in accordance with BS 7374 is recommended with a minimum permeability of 0.36 g / m2 per 24hr at 25°C and relative humidity of 75%. The method of assessment given in BS 5250 should be used to ensure that harmful condensation will not develop. If necessary, to overcome potential condensation risks, a vapour control layer should be incorporated within the structure.

Unsupported - This includes roofing underlays which are draped over the rafters or underlays laid over counterbattens on boarding or sarking. Roofing underlay should be of adequate water resistance and of tensile and nail-tear strength, low extensibility under the roof environment to produce the required resistance to wind uplift. It should conform to the requirements for type 1F or 5U given in BS 747.

Flexible underlays  - Underlays that meet the requirements of BS 747 or which have an UKAS-accredited-thirdparty- approved product certificate for their use in UK conditions should be used.  European Standard, EN 13859 part 1 includes the scope of BS 747 and materials not covered by BS 747.

Rigid underlays -   Products that have an UKAS-accredited-third-party-approved product certificate for their use in UK conditions should be used. A European Standard is being prepared for these products. When the European Standard is published products complying with the Standard should be used. Products, which fall outside the scope of the proposed European Standard, can be used provided they have an UKAS-accredited-third-party-approved product certificate for their use in UK conditions.

Battens and counter battens

Timber species -  The timber species should comply with type A or type B as specified in BS 5534 and should be treated where the Building Regulations and bye-laws require protection against the House Longhorn beetle. Suitable treatments are given in BS 5268 : part 5.

Note : Where there is a risk that timber moisture content will be greater than 22%, treatments that react with metal fixings should be avoided, e.g., copper chrome arsenate which reacts with aluminium.

Batten and counter batten sizes  Up to 600mm support centres the counter batten sizes should be 38mm by 25mm minimum and the batten sizes should be 38 (+3 / -3)mm by 25 (+ 3 /-0)mm.

Fasteners

Nails for tiles - Clout head nails of diameter 3.35mm and 2.65mm may be used and they should be a minimum of 38mm long. Clout head nails complying with BS 1202 part 1 (stainless steel), part 2 (copper), part 3 (aluminium) may be used.

Steel, or, galvanised nails should not be used for nailing tiles. Improved nails (annular, ring shank and drive screws) or screws may be used where the wind load calculation indicates that smooth shank nails will not meet the requirement.

Fasteners for fittings - Hip irons are hooks that fix to the lower end of the hip rafter and provide mechanical security for the hip tiles. The ridge tiles that are within 900mm of a gable or an abutment should be mechanically fixed. Suitable ridge tiles with wire fixing or lugs beneath tile ridge or with a proprietry dry fixing method should be used.

Nails and fasteners for securing battens to counter battens - Round wire nails complying with BS 1202 part 1, part 7 or hot dipped galvanised or stainless steel should be used. The nails are usually 2.65mm, or, 3.55mm in diameter and 65mm long, however, they may be longer to meet the requirements for wind loading. For exposed conditions improved nails, screws or helical fixings may be required.

Flashing and junctions - Where required, metal flashing and junctions should be fixed with copper or stainless steel nails. The size of the nails should be in accordance with the recommendations given in the Lead Sheet Manual, volume 1. Aluminium nails must not be used to fix lead flashing.  Flashing in exposed locations may need to be clipped and this should be in accordance with Lead Sheet Manual recommendations.