Roof Dip Between Rafters

Structurally inadequate or deteriorated over time.

Roof dip between rafters.

If you notice that there is a visible dip in your roof chances are you have a problem with one or several rafters and you may soon be facing more issues like water leaks bowed out walls or your roof caving in on you. And of course the amount of deflection. From the out side you can see a dip or maybe it can be described as a valley in the roof. My rafters are 16 oc and the roof is 4in12 plywood deck about 1 2.

Roof sheathing sags for the same reason any component of a home that spans between two bearing points sags. You can simply have the old sheathing replaced with better material when it s time for new roofing. The boards creating the slope of the roof are wider than lumber used to build trusses 2x8s 2x10s and 2x12s are most common in rafters vs. If the roof sags between the rafters or trusses the most likely cause is sheathing that s too thin for the area it covers.

Rafter boards are fastened to the ridge board at the peak and the top plate where they join the wall. Minor dips or lumps can also occur at hip ridges or valleys due to poor roof truss alignment or other framing problems. Many older homes were stick built with lumber sizes that would not pass code now. Undersized rafters also can cause sagging along the whole side or plane of a roof.

Remedies for a sagging roof. Because it was structurally inadequate when installed or has deteriorated over time. If a roof dips in between rafters or trusses it s probably because the sheathing is too thin for the span. Removal of the lateral bracing necessary for a roof rafters that are framed without a ridge beam will make the ridge dip noticeably as in the photo below.

Its about 2 3inches deep in the center. Someone said to me that the rafter might just have been installed. The fix here is to replace the thin sheathing with thicker sturdier sheathing. Between the rafters is a minor sheathing repair between eave and ridge is much more involved.

Repairing a roof rafter in this condition is not a hard project but it can be difficult if there is not easy access. In finished space insulation is placed between the rafter boards and drywall or other material is fastened to the face. If the framing is sound and problems are not found elsewhere but the roof still sags the problem might have originated because of poor installation of the plywood sheathing or shingles.