Then mark your post with the desired length in the middle of one side and run the blade of your saw through that mark. Using the angle you recorded in the attic, set your miter saw blade angle to match. Don't get too close to the end (3 inches recommended) as you don't want it to split - we're trying to prevent that.right? It's also a good idea to mark the center lengthwise - this will help line things up in the attic.Ĭompression post The role of the 4x4 compression post is to get the rafter back into its original position as much as possible as well as have a temporary resting place for the scab boards.

I used 3/8 inch bolts, so I drilled 1/2 inch holes to ease in the installation - 3 on each end in that last foot. Scab boards After you have cut the scab boards to length, drill a set of holes in one of the scab boards where you want the lag bolts to go. To make things easier in the attic (cramped, hot space), there are a few things that can be done down where's it's cool(er). This was a critical piece of the equation as the scab boards are heavy and if you're doing this by yourself, it's like having a third hand. The reason we're using a 4x4 post is so that after it's in place, you can rest your scab boards on top of it while you clamp them in place. The first measurement gets you the length of the support and the second one gets you the angle needed to make the support match the rafter as you force it into place. I used a piece of wood that was longer than the distance between the floor joist and the rafter and then just traced the angle on the side of that piece of wood. This will be different for every roof and will match the pitch of the roof. The angle of the rafter in comparison to the floor joists.the distance from the underside of the rafter to the joist beneath it - use the central part of the split as this is where the support will be most useful.There are two other measurements you'll need for the 4x4 compressions support post: Since the board will not be outdoors, it's not necessary to get pressure treated wood. At most home centers, 2圆s are sold in 8 foot lengths, which means I can get two 4 foot sections from one board - just right for the repair.Ī note about board selection To ensure the scab didn't fail in the same way the original rafter did, you should select your 2圆 with as little knots as possible and look for nice straight, horizontal grain. It's a good idea to offer at least a foot on either side of the affected area to get a good, long lasting scab. NOTE: It is useful to read this entire tutorial before attempting any of the steps as there are several pieces of information that are needed and going up and down into the attic is tiresome.įor the fix in this picture, the affected area was about 24 inches. Materials needed (2) scab boards cut to length (step 1) (6) 3/8-inch hex head bolts - 5.5 - 6 inches long (6) matching hex head bolt nuts (12) matching bolt washers (1) 4x4 post (2) wood clamps (1) sheetrock screw 1/2 inch wood bit (paddle or spiral) (2) box-end wrenches or sockets that match bolt/nut hammer battery-powered drill drill-press (optional) Step 1: Measure the affected area Step 2: Prepare the scab boards Step 3: Compress the rafter to original state (as much as possible) Step 4: Clamp the scab boards to the rafters Step 5: Drill lag bolt holes through all three boards Step 6: Install lag bolts with washers and tighten Step 7: Remove support and clean up The following steps ensure that the rafter won't fail and if this repair is part of a list from an inspection report, it will pass inspection. The important aspects of this repair is the length of the split as you will need to adequately cover it and provide enough length to your scab to get into good wood beyond the affected area.

Obviously, this is not a good situation as it can cause the entire roof to fail if not addressed. Overview From time to time, an attic rafter will split along a knot - typically after having a new roof installed because of the workers walking around on it.

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