Questions

There is no mandatory requirement to treat timber used in the manufacture of trussed rafters over most of the UK except for an area of the South East where insect attack from the Long Horn Beetle necessitates the use of treated timber.

The majority of trussed rafters manufactured in the UK are fabricated using European Whitewood which has been Kiln Dried to a moisture content of 12% and machine stress graded. The most common grade used is TR26 which is a specific grade for truss manufacture.

Common timber width for trusses is 35mm for truss spans up to 11.0m and 47mm for spans greater although there are other thickness restrictions for very long spans.

No. There is no mandatory regulations that require the use of a metal clip connection although the British Standards and the Trussed Rafter Association strongly recommend the use of a preparatory mechanical connection between the truss and the supporting structure. The main purpose of the connection beyond simple positioning is to resist uplift forces generated by wind loads. 

Skew nailing is a method of connection often seen but is not recommended. Firstly it is very difficult to apply proof calculations to a pair of skew nails and secondly there is very often damage caused to the nail plate on the eaves joint while hammering home the skew nails.

Glide shoes fitted at the bearing points of trusses allow a limited amount of horizontal displacement of the truss at the bearing. The raised tie design leads to flexing of the extended rafter members and as the truss tries to deflect this a horizontal force is generated at the bearing points. If the bearings were rigidly fixed to the truss this force would result in damage to the supporting structure and decoration. By introducing a sliding bearing mechanism such as the glide shoe the amount of horizontal force transposed to the wall is significantly reduced and thus minimises the potential for structural damage.

Unless otherwise noted all carpenters metalwork should be fully nailed using the special square twisted nails supplied. Other nails, such as plasterboard nails should not be used and could result in failure of the connection.

Never cut, drill or alter trusses.

Trusses are designed to support your roof, and are assembled from the highest grade of structural timber. Any such alterations may lead to premature failure and may end up costing hundreds of pound in engineer design fees and extra timber support to ensure the structure is strong enough for the required load.

If in doubt, please ask us before cutting. We will advise if any alteration is feasible.

We offer a full design service, to find out more contact us using our enquiry form, email us at info@stevensonandkelly.co.uk or call us on 01236 765614 to discuss your options.

You may wish to contact us using our enquiry form, email us at info@stevensonandkelly.co.uk or call us on 01236 765614 to discuss your options.

Trusses should be installed and covered as soon as delivered. They should be placed on bearers to keep clear of the ground. We don’t recommend storing trusses uncovered for longer than 1 month

easi-joist® floor joists are lighter and stronger than conventional timber and are precision made for convenience and labour saving.

Their unique wood and metal construction means you can run services like wiring and plumbing through them easily without the risk of structural weakening through drilling or notching as with conventional solid timber joists.

Virtually any load can be accouinted for but will need to be specified at planning stage to ensure correct load tolerances.

Stevenson & Kelly can offer many truss rafter alternatives and have successfully completed many projects successfully removing the need for costly steel and long construction times. Alternatively, we can design the attic using our trussed rafters and avoiding using steels completely.

Conventional attic conversions simply convert your existing space, so if you have restrictions such as a shallow roof pitch, the amount of space would be minimal. Room in the Roof solutions can create extra space by altering the pitch of the roof and building in such features as dormer and Vellux windows.

We would advise a stairwell opening at the design stage of your attic roof conversion. Any retrospective alteration could be costly, so it is best to include for these now. If you design your stairwell opening when installing the new trusses, this may cost extra initially but it will work out cheaper in the long run.