Thread: Scabbed rafters and building codes

This house was built in 2006. A potential buyer noticed that the sheathing in the valley was overlapped, the right side on top of the left side, which was noticeable at the eaves from the outside. The owner who is a roofing contractor decided to correct this problem so he or some of his crew took a circular saw and cut through the sheating to make it even and also cut through a total of 8 jack rafters. The rafters were scabbed back together. The valley rafter is also scabbed at the ridge, not sure when this happened. I'm making a rec to have a structural expert look at it. My client's question is: Is there anyway to piece these rafters together that would comply with code or do all of these scabbed rafters need to be replaced? The first pic is of the scabbed valley rafter at the ridge and the rest are of the jack rafters.

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Sean,

By looking at your pics the structural integrity of the home has been compromised and code or not I would recommend the rafters be replaced. Scabbing the rafters together is only a band-aid. Over time the nails on the scabs can become loose and sagging can possible occur in the valleys and areas of the roof. The right fix is to replace the rafters.

Frank Luzar
Home Inspector

Originally Posted by Sean Thornton

I'm making a rec to have a structural expert look at it.

Good.

My client's question is: Is there anyway to piece these rafters together that would comply with code or do all of these scabbed rafters need to be replaced?

Instead of "replacing the valley rafters, "new" valley rafters could be installed next to the existing valley rafters such that the "new" valley rafters go all the way from bearing to bearing.

Originally Posted by Frank Luzar

Sean,

By looking at your pics the structural integrity of the home has been compromised and code or not I would recommend the rafters be replaced. Scabbing the rafters together is only a band-aid. Over time the nails on the scabs can become loose and sagging can possible occur in the valleys and areas of the roof. The right fix is to replace the rafters.

Frank Luzar
Home Inspector

Agree that installing new one-piece rafters would be a "right fix". But if you have to take the roof off to get them in, then scabbing the rafters may be better, i.e., more practical and less costly, and should be a solid and acceptable fix if the added pieces overlap the cut members by several feet and are joined with hot dipped galvanised bolts and nuts in a structurally sound bolting pattern with appropriate torque and maybe with timber washers. Agree nails are not suitable as they could loosen over time, e.g with live loads, and shear forces, and suggest they only be used to hold the scabs in place temporarily while the bolt holes and bolts are being put in. If any doubt exists about the strength or bolts and bolt pattern of scabbing then consult a structural engineer.

Originally Posted by Frank Norman

Agree that installing new one-piece rafters would be a "right fix". But if you have to take the roof off to get them in,

A simple and inexpensive method to get long pieces of lumber into an attic is to cut a section of fascia out on the back where it is not seen much, pass the long pieces in to someone in the attic, and when the job is done install some blocking and seal that piece of fascia back in place. A little paint and no one even knows it was removed.

A simpler fix would be to run purlins/strongbacks under the splice point, with kickers to bearing walls, or to new structural beams at the ceiling level, but I recommend that a PE look at it to verify the adequacy of this solution.

The rafters can be repaired just as you would a damaged truss. Personally I would recommend that they get a structural engineer to design the repair and have someone ensure that the repair is done exactly as called for in the design.

In most cases it would not be practical to replace the rafters or to be able to get full length members alongside. Just trying to get the angle cuts in place for bearing would most likely require removal of the roof decking.

This would be unnecessary with a properly designed repair.