In most domestic roof construction today double-pitched rooves are used, with a symmetrical shape and a gable end laid with brick up to the roof edges.

At both Barratt and Westerman this type of roof were used.

To form the roof structure inclining timber rafters span from the eaves to the ridge where thay are attched to a ridge board spanning from gable to gable ends. For extra support horizontal ceiling joists are fixed to the rafter bottoms which in turn are supported by binders at right angles to the ceiling joists. Purlins are also used to support the rafters in mid-span from deflection from roof loads.

This has been the traditonal technique of roof construction for many years. However, this technique has been generally superseded by using trussed rafters.

Trussed rafters are pre-fabricated rafters with triangulation already in the design, therefore no further need for purlins, hangers or ridge boards, although binders are used to hold the separate truss rafters together as a structure. (seen alongside)

Trussed rafters are used because their pre-fabrication offers easy, lightweight and fast construction on site, no internal partition support is required and they are readily available and cheap.

Barratt have used a 'Fink' trussed rafter, illustrated above, 80mm by 40mm. The rafters are butt-jointed and held together with toothed plate fasteners by machines.

The rafters need to be fixed together and fitted to the walls. This was done with the use of a timber wall plate in the wall itself (as in traditional roof construction). The rafters are placed onto the wall plate at 600mm centres and clipped together with specially manufactured truss clips. Although fairly stable, further support is required by using binders as mentioned above.

The binders used are similar to those in the traditional construction as they run at right-angles to the rafter for extra support. Barratt have fixed a binder at the top of the rafters (like a ridge board) but it is fixed underneath the two adjoined rafters. These can be seen running along the top of the rafters in the photo alongside.

By adding the binders the trussed rafters have become linked together, but as yet they are still susceptible to wind deformation in the top part of the roof.

To counteract this problem it is common practice to add diagonal bracing to the structure to gain rigidity. Barratt have nailed diagonal timber bracing under the top rafter on each side of the truss. (shown opposite)

Barratt have finished the roof structure with overhanging verges as well as overhanging eaves. Barratt have used a pre-fabricated timber gable ladder which is nailed down to the end rafter and the remainder of the ladder cantilevers over the verge, shown alongside.

Barratt have fitted soffit and fascia boards for protection to the roof structure an also for aesthetics.

The roof is then covered in insulation and a black nylon weave roofing felt, to prevent water penetration, which is wrapped around the fascia board and held in place with horizontal timber batons nailed to the rafters.

Because the roof is insulated, condensation may occur, therefore ventilation is required to remove moist air from inside the roof. Barratt have ventilated the roof at the eaves by installing vent strips onto the soffit board.

Barratt have finished the roof in black concrete interlocking tiles. The tiles obviously by their name, interlock with each other with an approximate 75mm overlap, creating a good structure and good waterproofing.

The photo adjacent shows the tiles being laid. The workmen have stopped whilst the dormer window is constructed.

At the top of the roof a different types of tile is laid. Barratt have used red half-round ridge tiles which provide good watertight joints. They are embedded in mortar at the ridge with the end tiles having wire inside them which are nailed to a baton in the roof. The ridge tiles can be seen on the photo opposite.

At the verge of the roof Barratt have filled the gaps with mortar pointing.

Rainwater will inevitably fall in England, therefore it is essential to provide a rainwater system to remove the water from the property.

Barratt have fitted plastic fixed box shape guttering onto the fascia board to collect rainwater from the roof. The water then flows along the horizontal gutter to a plastic vertical box-shape gutter which takes the water away to the underground drainage system. Both gutterings are held in place with plastic support brackets.

Westerman have also constructed their double pitched rooves with trussed rafters.

Westerman have also used 'Fink' trussed rafters, 80mm by 40mm with butt-joints holding the timbers together with toothed plate fasteners, shown alongside.

Like Barratt, Westerman fixed the trussed rafters together on a wall plate. The rafters are agin placed onto the wall plate at 600mm centres and clipped together with specially manufactured truss clips. Westerman also use binders for further support in the structure.

Westerman have fixed a binder underneath the top rafter, and two others along the ceiling joists. The lower binders have been constructed from 2 pieces of timber, therefore, Westerman have overlapped the binders by at least two rafters.

Westerman have also used diagonal bracing in the roof to gain further rigidity (all shown alongside).

Like Barratt, Westerman have used straps to tie the roof structure to the end gable walls to prevent movement of the walls and roof structure by wind.

The roof covered in insulation and a black nylon weave roofing felt to prevent water penetration which is then in place with horizontal timber batons nailed to the rafters.

Westerman also ventilated the roof at the eaves by installing vent strips onto the soffit board.

Westerman have finished the roof in red interlocking concrete tiles with an approximate 75mm overlap.

At the top of the roof Westerman have used red half-round ridge tiles which provide good watertight joints. Again they are embedded in mortar at the ridge with the end tiles having wire inside them which are nailed to a baton in the roof.

At the verge of the roof Westerman have used mortar pointing.

Westerman have installed plastic half round guttering onto the fascia board to collect rainwater from the roof. The water then flows along the horizontal gutter to a plastic vertical round gutter which takes the water away to the underground drainage system.