Bs 5268 Part 2 Free Download

Items to be taken into account include: (a) dead and imposed loadsDead and imposed loads should be calculated in accordance with BS 6399: Part 3. Dead loads include the self weight of the roof structure and the roof covering. Imposed loads include snow loadings and the weight of water tanks, insulation, etc.Structural timber should be specified according to the strength classes in BS 5268: Part 2. Timber specifications when using BS 4978 grading rules (eg GS) should also include the timber species. The strength class can then be determined from Table B1 in Approved Document A1/2 to the Building Regulations or Table 3 in BS 5268: Part 2. (b) wind loadsWind loads appropriate to the site location should be calculated in accordance with BS 6399: Part 2.

• Bs 5268 Part 2 Free Download For Pc
• Bs 5268 2 Free Download

The roof should be designed to resist wind uplift. This resistance is often provided by the weight of the roof itself but holding down straps should be provided where the self weight of the roof is insufficient. (c) holding down strapsHolding down straps are required in Scotland, Northern Ireland and other areas of severe exposure. Some roof covering manufacturers provide detailed guidance.Where holding down straps are necessary, they should have a minimum cross section of 30mm x 2.5mm and be fixed at maximum 2m centres. Steel straps with a galvanized finish are normally acceptable. The design should detail how straps are to be fixed and what materials are to be used. The durability of fixings should be compatible with the straps.

(d) sizing and spacing of membersSizing and spacing of rafters and ceiling joists should be as:. for trussed rafter roofs. for traditional cut roofs.Generally, the spacing of rafters and ceiling joists should be not more than 600mm. The spacing of ceiling joists should suit the thickness and size of the plasterboard sheets or other ceiling finish.

Bs 5268 Part 2 Free Download For Pc

Plasterboard sheets may be fixed at the following joist centres:. 9.5mm sheets- up to 450mm spacing.

12.5mm and 15mm sheets- up to 600mm spacingProprietary roof systems should be designed by an Engineer in accordance with. (e) size and spacing of tile battensThe size and spacing of tile battens should be in accordance with the roof covering manufacturer's recommendations, but not less than shown in the table in.Nails for fixing battens should be 3.35mm (10 gauge) x 65mm long. Galvanized smooth round nails are acceptable, except where the maximum basic wind speed is over 48m/s (from BS 6399: Part 2), when ring shank nails should be specified. Items to be taken into account include: (a) wall platesNormally, trussed rafter roofs and traditional cut roofs should be supported on timber wall plates.Wall plates should be as detailed in Clause D6(b) with regard to the table concerning minimum sizes. Fixings to connect the roof structure to the wall plate should be specified having regard to the roof construction and the exposure conditions of the site.For trussed rafter roofs not subject to uplift, the minimum fixing should be two 4.5mm x 100mm long galvanized round wire nails, skew nailed, one from each side of the trussed rafter. Alternatively, truss clips can be used, fixed in accordance with manufacturers' instructions.In Scotland, nails should be appropriate to wall plate dimensions.

(b) holding down strapsIn situations where the roof is required to resist uplift, skew nailing is unlikely to provide sufficient strength. Appropriate metal straps should be used. (c) lateral restraint strapsFor dwellings of masonry construction, restraint should be provided at rafter level for gable walls. Larger gable or separating walls may also require restraint at ceiling level.Guidance in assessing when ceiling restraint is needed can be found in Building Regulations.Lateral restraint straps should have a minimum cross section of 30mm x 5mm and a minimum anchorage down-turn of 100mm. The level of galvanizing for straps and their fixings should be in accordance with BS 5628: Part 3 (reference should be made to ). Sheradizing is not acceptable in Northern Ireland and the Isle of Man.

Straps should be of sufficient length to be fixed to three trusses and should be fixed with solid blocking.In framed roofs, as an alternative, purlins and pole plates can also provide restraint if the timber abuts a gable construction. Where purlins are used to provide restraint they should not be spaced at more than 2 metre centres, unless the design shows they are adequate at greater spacing.In trussed rafter roofs, an alternative is to provide restraint through gable ladder detailing. (d) timber frame constructionFor dwellings of timber frame construction, the designer should ensure stability in accordance with BS 5268. Items to be taken into account include: (a) recognised design standardsTrussed rafters should be designed in accordance with BS 5268: Part 3. Truss manufacturers may have their own computer programs for calculating truss designs in accordance with the British Standard. Items to be taken into account include: (a) recognised design standardsSizes of certain roof members for basic pitched roofs are given in TRADA publications and BS 8103.Where spans, sizes, spacing or strength classes of timber are outside the scope of the tables in the statutory regulations or where the form of roof is other than a basic pitched roof, the roof should be designed by an Engineer in accordance with.

Calculations should be based on BS 5268: Part 2. (b) member sizesUnless the roof is designed by an Engineer in accordance with, traditionally, nominal sizes of members would be as follows: MemberMinimum size (mm)Struts and braces100 x 50Wall plates (Scotland)100 x 25Wall plates (Northern Ireland & the Isle of Man)100 x 38Wall plates (other)75 x 50Hipsrafter cut + 25Valleys32 thickRidgesrafter cut + 25(c) triangulationIn the design of a cut roof, timber members should be triangulated or otherwise arranged to form a coherent structure. All forces inherent in the design should be resolved. The method of fixing or jointing members should be specified.Particular care should be taken to ensure adequate triangulation when designs incorporate hips and valleys, and when cut roofs are used in conjunction with trussed rafters.Details of all structural members should be provided. (d) strutting to cut roofsAny part of a cut roof which forms a floor should have strutting in accordance with. Items to be taken into account include: (a) treatment against House Longhorn BeetleIn some areas of the UK, treatment against House Longhorn Beetle is required. Reference should be made to relevant Building Regulations.

Reference should also be made to. Items to be taken into account include: (a) weathertightness of roof coveringsRoofs with a tile or slate covering should be designed in accordance with BS 5534: Parts 1 and 2. (b) tilesFor tiled roofs, the pitch, gauge and lap should be within the limits given in Table 1 of, unless the manufacturer specifies otherwise.Fixings for single and double lap tiles should be designed in accordance with BS 5534 and BS 6399.

Where tile manufacturers have computer programs based on these British Standards, their recommendations should be followed.Tables 2 and 3 of contain minimum fixings for tiles. The tile manufacturer will be able to advise on any additional nails or clips required for a particular location. A fixing schedule produced by the tile manufacturer, based on The Zonal Method, is acceptable.

(c) slatesNatural slates should be fixed in accordance with BS 5534 and BS 6399. Each slate should be nailed twice when centre nailed.

Bs 5268 2 Free Download

(d) roof coverings other than tiles or slatesLead sheet roofing should be in accordance with BS 6915.Other types of sheet roofing should be in accordance with the relevant parts of CP 143.Roofs with the following traditional coverings should be designed in accordance with satisfactory custom and practice:. natural stone. shingles.

thatch.Thatching should be as recommended by the Thatch Advisory Service or other appropriate authority in accordance with.Proprietary roof coverings should be assessed in accordance with. (e) roof underlaysAn underlay should be provided for all tiled roofs.The underlay may be felt to BS 747 or a proprietary sarking membrane complying with. Some proprietary roofing underlays have a higher vapour resistance than bitumen felt and may need additional roof ventilation. Where the underlay is exposed, such as at the eaves, a type 5U felt should be used.

A type 1F felt may be used for the remainder of the roof.To prevent the underlay sagging at the eaves and forming a water trap behind the fascia, it is recommended that the underlay is supported by a continuous fillet. Where the pitch is below 30°, a continuous support fillet should be provided. (f) rigid sarkingIn areas of severe exposure, a rigid sarking with underlay is recommended and is normal practice in Scotland.The choice of rigid sarking should take account of the type and fixing of the roof covering. Items to be taken into account include: (a) moisture barrierA moisture barrier should be provided behind all vertical tiling and slating.Moisture barriers should be:. underfelt or equivalent where the wall structure is brickwork or blockwork. a breather membrane where the supporting structure is of timber construction.For detailed information on the use of moisture barriers in association with timber frame construction, reference should be made to.

(b) batten sizeBatten sizes should comply with (e). (c) fixingEvery tile or slate should be nailed twice and comply with the general requirements of BS 5534. (d) weathering detailsBottom edges should be finished with an under-course tile. At dormer cheeks, the tiles or slates should be specified to be cut close to the slope of the roof, over a flashing fixed to the side of the dormer.At internal or external angles, purpose made corner tiles or soakers should be used to form a weathertight joint.Where pitched roofs abut masonry walls, a stepped flashing should be specified, turned behind the tiles. Details are shown in.For information regarding vertical tiling or slating on walls, reference should be made to (Design and Sitework). eaves ventilation should be provided on opposite sides of the roof to permit cross ventilation. Reference should be made to (a) for illustrations showing where ventilation should be provided.

where the roof pitch is 15° or more, cross ventilation should be provided to the roof void equivalent to a 10mm slot running the full length of the eaves. where the ceiling follows the slope of a 'cold roof' regardless of pitch or where a cold roof has a pitch less than 15°, cross ventilation should be provided to the roof void equivalent to a 25mm slot running the full length of the eaves. At least 50mm clearance should be maintained between the insulation and the roof underlay. where the roof pitch exceeds 35° or when the span exceeds 10m, high level ventilation, equivalent to a continuous 5mm opening, should be used in addition to eaves ventilation.

the means of providing cross ventilation to mono-pitched roofs should be in accordance with BS 5250 which indicates eaves ventilation together with the equivalent of a continuous 5mm slot at high level.For cold roofs that incorporate a low water vapour resistance (type LR) underlay (e.g. A vapour permeable underlay). ridge or high level ventilation equivalent to a continuous opening of 5mm should be provided, unless the underlay has been assessed in accordance with Technical Requirement R3 and the assessment confirms that this is not required.(b) position of vapour checksVapour control layers should be used in roof constructions where the ceiling board is fixed to the rafters and insulation is placed between the rafters.In normal pitched roofs where insulation is placed at ceiling level and the void above is ventilated, a vapour control layer is not recommended.

Moisture from the dwelling will be diffused through the ceiling and removed by roof space ventilation.Vapour control layers, where required, should be placed on the warm side of insulation. (c) ventilation of dormersPitched dormers should be ventilated from eaves to eaves or, where necessary, from eaves to ridge.Flat roofed dormers of cold deck construction should be ventilated. The ventilation path should not be blocked by the timber structure, strutting, etc (reference should be made to (Design and Sitework)). (d) methods of ensuring unobstructed ventilationVentilation openings where the least dimension exceeds 10mm should be protected to prevent the entry of birds, etc.Acceptable protection of openings can be provided by using materials complying with (j).A spacer in the eaves should be used so that ceiling insulation can be installed over and beyond the wall plate. This minimises the cold bridge without blocking the ventilation.(e) other methods of reducing condensationMethods of reducing condensation, such as draughtstripping loft hatches and sealing holes for services, are given in. Items to be taken into account include: (a) roof coveringsSlates and concrete or clay tiles are designated AA when tested to BS 476: Part 3 and therefore can be used without limitation on any pitched roof. The use of some other materials is restricted by statutory requirements, particularly in relation to their distance from site boundaries (reference should be made to Building Regulations).

These include:. bitumen felt slates. wood shingles. thatch.(b) chimneys and flue pipesCombustible material, such as roof timbers and sarking felt, should be kept away from heat sources as described in (Design). The junction between a separating or compartment wall and a roof should be firestopped. If there are gaps, fire, smoke and flame can spread from one compartment to the next across the wall.Mineral wool fire-stopping should be used to allow for movement in the roof timber, and avoid 'hogging' of the roof which is often associated with mortar fire-stopping.Where a wall separates an integral garage from the rest of a dwelling, other arrangements are possible provided the principle of half-hour fire separation is maintained. Access should be provided to:.

the main roof space, and. roof voids that contain cisterns, tanks and the like.Access is not required to other roof voids containing only water pipes. SIZE OF OPENINGSAccess openings should be not less than 520mm in any direction.Where equipment (e.g. Heating and ventilation equipment) is located in a roof space the size of the opening should permit its removal.Access openings should not be located directly over stairs or in other hazardous locations. PROVISION OF WALKWAYSBoarded walkways should be provided. Items to be taken into account include: (a) provision of gutters and downpipesRoofs greater than 6m 2 in area should be provided with rainwater gutters and downpipes. Consideration should also be given to the provision of rainwater drainage to roof areas less than 6m 2, for example dormer and porch roofs.

(b) sizesGutters and downpipes should be of sufficient size to accommodate normal rainfall.Care is needed in sizing gutters where dormer roofs interrupt the run-off from a pitched roof. The gutter should be sized to cope with the concentrated flows. (c) discharge from one roof to anotherWhere water from a large roof surface discharges onto another surface, precautions should be taken to prevent erosion of the lower surface. (d) discharge into drainage systemUnless designed otherwise, shoes should be provided to rainwater downpipes.