Using I Joists For Roof Rafters

10d box nails may be substituted for 8d common shown in details.

Using i joists for roof rafters.

As a structural engineer i have inspected many roofs framed with i joist rafters but very few that have not needed a correction due to the i joist bearing. Use single i joist for loads up to 2000 plf double i joists for loads up to 4000 plf filler block not required. The first thing to understand is how a roof framed with wood i joists differs structurally from a tradi tional stick framed roof. While typically not a problem when the roof is flat and the i joists bear perpendicularly on the top plate when the rafters are sloped proper bearing becomes an issue.

Attach i joist to top plate using 8d nails at 6 o c. In a typical roof framed with dimension lumber the rafters rest on the exterior wall top plate at the lower end and bear against a ridge board at the top. I joists make for a strong flat roof but you have to pay attention to the connections at the ridge and eaves. The manufacturer would need to design the repair.

By the end of the class about 90 minutes they had two thirds of the tji roof rafters cut and ready for installation. Tj 9510 installation guide for floor and roof framing with tji s31 s33 and s47 joists east canada. The diagram provided by bruce is an example of special requirements. Photo 2 shows a view of the other ends of these same i joist rafters and the use of.

A framer s guide to the installation process. 9030 floor framing standards guide. The one that is cut might be a problem. Yes you can use them for rafters they have to be installed per the manufacturers guidelines.

These i joist rafters are on 24 inch 61 cm centers and support plywood roof sheathing and wood shingles. When wood i joists are used as rafters connections at the structural ridge and the tops of exterior walls must be detailed properly. Tj 9001 installation guide for floor and roof framing with tji 110 210 230 360 and 560 joists. Making top cuts in the i joists to make the short rafters one person held the tji down to the horses while another one made the cut.