In Between Rafters Bridging For Roof

Position the foam board between the rafters and push it upward until it fits snugly against the underside of the roof deck.

In between rafters bridging for roof.

Solid blocking and metal or wood x type bridging do accomplish the same task. The same concept holds true for roof trusses. The roof rafters provide integral structural support to the roof. Rafter span tables use these tables to determine lengths sizes and spacing of rafters based on a variety of factors such as species load grade spacing and pitch.

Installing stacks of rigid foam between rafters is slow fussy work but it might make sense for a do it yourselfer. As roof pitch is lowered the weight burden on the rafters increases. For instance if your roof has a steep pitch you may be able to use 2 inch by 4 inch rafters but if your roof has a low pitch building code may require that you used 2 inch by 6 inch or 2 inch by 8. Now if you re retrofitting an existing building this could get tricky real fast.

Install underlay above the rafters. Visit the roof framing page for more information on cutting roof rafters and visit the roof pitch calculator for determining rafter lengths based on rise and run. Insulation between the rafters. The blocking or bridging between joists or rafters also contributes to this phenomenon.

For example with bridging installed between joists a piano leg sitting over one 2 10 is actually supported by several. Before you cut your boards you ll need to measure the width of your building and calculate the exact length of each rafter. For low pitch roofs building codes may require larger dimension rafters. Insulation is placed between and hopefully above the rafters or joists with sometimes extra insulation underneath along the ceiling.

The snugness of the foam itself should be sufficient to hold the strips. For an un ventilated roof construction a vapour open underlay or breather membrane should be specified. Common spacing for trusses on this type of building is often between 2 and 4 feet but trusses built with advanced designs may allow spacing as great as 8 or 12 feet. So the space between rafters can be greater without reducing the maximum span.

Fine homebuilding finding effective ways of beefing up under insulated roofs is a perennial problem affecting countless houses built to minimum energy standards.