Using I Joists For Roof Rafters

The first thing to understand is how a roof framed with wood i joists differs structurally from a tradi tional stick framed roof.

Using i joists for roof rafters. All nails shown in the details above are assumed to be common nails unless otherwise noted. 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. These i joist rafters are on 24 inch 61 cm centers and support plywood roof sheathing and wood shingles.

First they made i joist cross cutting jigs from osb scraps and made a few practice cuts. 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. 10d box nails may be substituted for 8d common shown in details.

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. The manufacturer would need to design the repair. When wood i joists are used as rafters connections at the structural ridge and the tops of exterior walls must be detailed properly. The one that is cut might be a problem.

I joists make for a strong flat roof but you have to pay attention to the connections at the ridge and eaves. Usp994 131 usp connector guide for trus joist. 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. 9030 floor framing standards guide.

Photo 2 shows a view of the other ends of these same i joist rafters and the use of. Yes you can use them for rafters they have to be installed per the manufacturers guidelines. Use single i joist for loads up to 2000 plf double i joists for loads up to 4000 plf filler block not required. A framer s guide to the installation process.