As a roofing company, we require a flat roof surface prior to truss erection. This means that by the time we start erecting the trusses, the walls need to be at the correct wall plate levels.
Article by Henri Pretorius, LCP Roofing Sales Representative.
What does this mean?
The brickwork at the wall plate should be level and not sloping up or down, so that we are able to put a 38 x 76 piece of timber flat on top of the wall. Trusses are erected onto the wall plate once it is in place. We then extend a line from the first to the last truss in the sequence so that all the trusses in between can be lined up accurately with a level surface at the top. Battens or purlins will then go on top of the trusses.
Should the top of the wall be tapering downwards or upwards, the roof will follow the same tapering movement off the wall. The roof will be perpendicular to the walls, but should still follow a straight line at the apex, so that no waves in the surface are created. If the walls are not at spirit level, the roof will also not be at spirit level.
Lintels and roofing levels
Many builders do not place the correct number of bricks above a lintel or over an opening; the minimum number of bricks above a lintel is six courses. This course number will also be determined by the size of the opening; if the opening is too large for lintels, a concrete beam will be required.
If the lintel is not strong enough over the opening, the roof will sag along with the lintels once the tiles are laid. In many cases, the lintels will begin to sag even before any weight is applied to the walls.
Above all, we recommend that builders follow the National Building Regulations and SANS requirements.
We also recommend that wall plate levels are at a minimum of three courses higher than any slab that is destined to support the roof. This will allow the contractors to screed and waterproof the slab and still have enough space for water to flow downwards and not back onto the roof.
Some unscrupulous builders don’t mind taking short cuts, even if this means deviating from the regulations that govern our trade. At LCP Roofing, we prefer to do things right the first time, as fixing work that has not been done according to standards can have huge cost implications after the homeowner has moved in.
For more information, visit www.lcproofing.co.za.