I’ve run into an interesting situation with my current house reno, and I’m curious if any of you can help me out. The situation is this: we have a 1970’s modular (I’m done with them, this is my second), with an addition that was added not too long after. For whatever reason, the builder made the addition shorter by about 3 ½” (both the inside ceiling height and roof). I am rebuilding the addition’s roof structure (among other things), so that I have one solid roof deck and a matching ceiling height in our primary suite (I’m also completely redecking the roof so it’s solid).
The modular roof is a 3:12 truss system, and the old addition is rafters 2”x6” – 16” OC. The new roof has to be 2”x8” – 16” OC to meet the snow load, which I think is overkill at 42.5 lbs in my area.
Here is my current plan:
I’m going to build up the top plates of the addition with 2 – 2″x4″’s and a strip of ½” plywood (from the old roof deck). I was all good with this plan until I realized my rafter seat cut was too deep (it would require a notch much more than 1/4 the depth of the 2″x8″). I can fix this by making the plumb cut on the seat 2 ⅜” less, but that means my truss top chord is now 2 ⅜” short of my rafter top chord.
To fix that, I’m thinking I can rip down a 2x to the 2 ⅜” I need and nail it to the top chord of the truss. I’m concerned if that would be allowed by code. I’m also not certain what fastener I should use (probably 3.25”x0.131” smooth nail and glue it additionally). Another part of this is that I would like to use 14’ stock, but that would be a bit less than 2” short of my truss’s line length. I wouldn’t think it would matter if my deck was that short as it will be covered by the ridge vent anyway.
Does this pass muster? Would you do it differently? (while burning the whole thing down is tempting, I think it would just end up costing me more)
Thanks for the insight!
Replies
Wrapping my head around this a bit. If you shift the plumb cut, aren’t you effectively moving the roof surface up and out? Put differently, if you shim between the rafter and the top chord as you suggest, you are just increasing the unsupported sheathing above the top chord... again, moving the roof surface up/out. So it seems like your idea is intended to avoid moving the roof surface, but that sounds like what you’re doing. Did this problem arise from adding height to the top plate? It feels like the extra 2x’s on the top plate created this issue. If you change that strategy, can you get back to the acceptable notch, and line up the roof surfaces, without moving the rafters outwards? Put differently, start with the roof deck, and work down to the top plate, with the code-acceptable notch. You may not line up your interior ceiling perfectly, but is solves the roof and structural problem you are dealing with.
I used the wrong term. I was referring to the heel cut when I said plumb cut. So I would just be moving the rafter vertically.
Yes, in a way, adding to the top plate caused the issue. However, I only added to that so that I could have an even ceiling across the room (the addition extends one room).
At the moment, since I haven't been able to get ahold of my inspector, I'm planning to go with your thinking of working down from the original roof deck. However, I'm thinking I can move my rafter tie/ceiling joist up so that only a portion of the ceiling will be unmatched. I'll then just drywall over the angle that creates between the wall and matched ceiling elevation.