Thread: Proper support for Tile roof question..

I did an inspection today on a new construction and noticed that the support for the clay tile roof (2x8 rafters) were 2x4's . I don't think that would be acceptable and wanted to make sure that I wrote it up properly..

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What "support" are you talking about?

Support for roof rafters in the attic

The picture doesn't show enough to make the call. From what's pictured, the 2X4s aren't supporting the roof. They may be a mid-span support for the rafters or could just be leftover bracing from time of construction.

It's really a design question that we'd need a lot more information for to give an answer.... also goes way beyond a standard home inspection.

Purlins must be the same size (or greater) than the rafters that they support.

However, if the rafters are properly sized to span unsupported, the purlins may not be necessary.

I am not able to copy and paste the actual wording, but the section is:
IRC 802.5.1

You would have to check the span of the rafters. If the span calls for a 2 x 4 and some one installs a larger rafter then a 2 x 4 purling is right. I have wrote it up wrong before and the builder showed me where I was wrong.

R802.5.1 Purlins.
Installation of purlins to reduce the span of rafters is permitted as shown in Figure R802.5.1. Purlins shall be sized no less than the required size of the rafters that they support. Purlins shall be continuous and shall be supported by 2-inch by 4-inch (51 mm by 102 mm) braces installed to bearing walls at a slope not less than 45 degrees from the horizontal. The braces shall be spaced not more than 4 feet (1219 mm) on center and the unbraced length of braces shall not exceed 8 feet (2438 mm).

Roofs can be built to code (i.e. the purlins should be 2x8 to match the rafter size) or they can be built to engineered specs. R802.5.1 is controlling if the installation of the purlins is to reduce rafter span. If it is just to reduce deflection (e.g. making what would otherwise be an L240 span an L360) or as a temporary brace that wasn't removed then it's probably not a reason for concern.

I would make a note that the roof rafters appear to have undersized purlins and that the installation should be verified that it matches the engineered design. No engineered design? Then the roof installation should be verified that it is adequate to support the load - have them get a stamp from an engineer saying the design is kosher since it's not "built to code."