BS 747:1994 download free.pecification for Roofing felts.
1 Scope
BS 747 specifies requirements for roofing felts intended for use in the British Isles and countries with similar climate.
2 References
BS 747 incorporates, by dated or undated reference, provisions from other publications. These references are made at the appropriate places in the text and the cited publications are listed on the inside back cover. For dated references, only the edition cited applies; any subsequent amendments to or revisions of the cited publication apply to BS 747 only when incorporated in the reference by amendment or revision. For undated references, the latest edition of the cited publication applies, together with any amendments.
3 Class 1. Bitumen felts (fibre base)
3.1 Introduction
The felts in this class are:
iF reinforced bitumen felt
1 F reinforced bitumen felt, aluminium faced.
They are made from a continuous roll of unproofed, absorbent fibre.
Minimum masses for the base and bitumen components are given in Table 1.
3.2 Requirements for constituent materials
3.2.1 Base
The base shall consist of animal or vegetable fibres made into a close-textured absorbent sheet of fibre felt.
3.2.2 Saturating material
The saturating material shall consist of bitumen conforming to BS 3690-2 having a penetration within the range 60 to 230 at 25 °C when tested in accordance with BS 2000-49.
3.2.3 Coating material
The coating material shall have a softening point (ring and ball test) within the range 80 °C to 120 °C when tested in accordance with BS 2000-58 and shall consist of oxidized bitumen conforming to BS 3690-2 which may be stabilized with finely divided mineral filler. The proportion of stabilizing mineral filler shall not exceed 40 % by mass of the coating material.
3.2.4 Mineral filler
The mineral filler shall consist of finely divided mineral matter of which not less than 99 % by mass passes a 212 pm mesh BS sieve conforming to
BS 410.
3.2.5 Surfacing material
The surfacing material shall consist of a suitable quality of natural sand, mineral granules or other suitable material according to the type of felt.
3.3 Type iF reinforced bitumen felts
3.3.1 Description
iF felt is a bitumen saturated and coated fibre base felt combined with a layer of jute hessian embedded in the coating on one side of the felt so as to reinforce and strengthen the sheet. The sheet is surfaced with a surfacing material to prevent the felt sticking in the roll. The presence of the hessian is obvious on inspection.
This felt is also manufactured with an aluminium foil face on the hessian reinforced side to provide a reflective insulation hessian-reinforced under-slating felt.
3.3.2 Uses
iF felt is suitable for use under tiles or slates, particularly when the felt is not fully supported by boarding. It is not recommended for external use.
3.3.3 Reinforcement
The jute hessian to be used shall have a nominal
mass per unit area of not less than 110 g/m2.
3.3.4 Mass
The nominal mass per unit area shall be 15.0 kg per 10 m2 exclusive of wrappings or accessories. The mass of roll determined by the method in A.1 shall be not less than 95 % of that calculated from the nominal mass per unit area. Masses per unit area of components and their corresponding values shall be as shown in Table 1 when determined by the method of A.3.
3.3.5 Standard packages
The felts shall be marketed in rolls I m wide, in lengths of 15 m. The packages shall be marked with the name of the manufacturer, the number and date of this British Standard, i.e. BS 747:1994’, the type of felt and the nominal length and width of the roll.
3.3.6 Colour code
iF felt shall be Provided with a single continuous margin, of up to 50 mm of white surfacing along the length of the roll and on the inside convolutions of the roll so as to be visible when unrolled. The white surfacing shall provide sufficient contrast with the surface material to be easily distinguished.
4 Class 3. Bitumen felts (glass fibre
base)
4.1 Introduction
The felts in this class comprise the following types:
3B fine granule surfaced bitumen glass fibre felt
3E mineral surfaced bitumen glass fibre felt
3G venting base layer bitumen glass fibre felt These felts are made from a base consisting of a sheet of bonded glass fibres which does not require saturating as with class I felts.
In the manufacturing process coating material is applied to both sides of the sheet and is immediately surfaced with the appropriate surfacing to prevent the layers from sticking together in the roll.
4.4.4 Standard packages
The felts shall be marketed in rolls 1 m wide, in lengths of 10 m. The packages shall be marked with the name of the manufacturer, the number and date of this British Standard, i.e. BS 747:19942), the type of felt, and the nominal length and width of the roll.
4.4.5 Colour code
3E felt shall be provided with a single continuous strip of red surfacing along one longitudinal edge of the roll so as to be visible when unrolled. The red surfacing shall provide sufficient contrast with the surfacing material to be easily distinguished.
4.5 Type 3G venting base layer bitumen glass fibre felts
4.5.1 Description
3G felt is a bitumen coated glass base felt (specially perforated) which is covered on one side (the lower surface) with mineral granules and on the other side with surfacing material.
It is produced with 25 mm diameter perforations positioned at approximately 75 mm to 85 mm pitch throughout. A margin is normally provided to facilitate lapping of joints.
4.5.2 Uses
3G felt is suitable for use as the first layer in built-up roofing specifications when partial bonding and/or venting of the first layer of built-up roofing is required.
4.5.3 Mass
The nominal mass per unit area shall be 26 kg per 10 m2 exclusive of wrappings or accessories. The mass of roll determined by the method in A.1 shall be not less than 95 % of that calculated from the nominal mass per unit area. Masses per unit area of components and their corresponding values shall be those shown in Table 2 when determined by the method in A.3.
4.5.4 Standard packages
The felt shall be marketed in rolls 1 m wide and 10 m long. The packages shall be marked with the name of the manufacturer, the number and date of this British Standard, i.e. BS 747:19942) the type of felt, and the nominal length and width of the roll.
4.5.5 Colour coding
3G felt shall not be colour coded.