Morning all, quick reality check in case what I plan to do will destroy my walls.
Setup: existing rafters 2×6 @ 22″oc, 16′ (yup you read that right) on 8/12 roof. Ceiling joists 2×6 @ 16″oc. Everything toe-nailed into 4×4 top plate. CJs not tied directly to rafters. Rafters are showing stress around the toe-nails
Plan, in preparation for insulating roof deck: 12′ 2×6 sisters on rafters to stiffen them up. For strengthening connections to top plate, my plan is Simpson hurricane ties, preferably H10 (custom-sized) if it goes high enough, otherwise 2 H2.5A connectors. Each H10 would require 8 8dx1.5 nails into top plate, each H2.5A would require 5 8dx2.5 (that’s 10 nails per rafter).
Now the tricky part: the finished room below (ceiling down) has original plaster walls that I don’t want to lose. Plan is to use angle grinder and diamond blade to cut the plaster about 2-1/2″ down, remove plaster and lath (plaster already badly damaged near the top from previous remuddling), attach hurricane ties to top plate, fur out, new ceiling, then molding to cover the dirty deed.
Is this scheme (a) SOP (b) utterly insane (c) somewhere in between?
Thanks for any advice.
Replies
can you go on the outside of house
No I would have to tear off the soffits, redo, repaint. Very big job, I got an estimate of $4-5K from someone who said he had better things to do.Edit: Given I'm most concerned about the "F2" force (as Simpson calls it) from the inside out, I'd rather install these on the inside. Having said that, there a few places where there may not be enough room to fasten the ties because of the ceiling joists.Old house maintenance is for masochists.
Edited 4/23/2006 11:16 am ET by Taylor
As another approach, if you can somehow get a gun in there, shoot each rafter to the ceiling joists with at least 3 nails (code where I am calls for minimum of 3 8d at each connection -- I'd go with 3 12d 'cause I have boxes of 'em).
Then tie each CJ to the top plate and stud below with a connector (you can use either the H series or the LTS/MTS/HTS -- give Simpson a call and they will tell you exactly what you want to be using -- I'd recommend the LTS/MTS/HTS series to make sure of catching the stud below).
Just another option.
"Let's get crack-a-lackin" --- Adam Carolla
From what I can find, code says:
each CJ 3 x 8d toe-nailed to the top plate
each rafter 2 x 16d toe-nailed to the top plate
each CJ 3 x 16d end-nailed to the corresponding rafter
Looks like I have the first two, not the third. My problem is, different spacing on rafters and CJs. I had a thread on this a while back, hurricane ties came out as the solution, now I'm having problems implementing that. Anyway a single H2.5A gives less strength in the F2 direction than 1x16d nail. I've looked at other connectors (A23, A33) but the existing nails get in the way of installing them cleanly (danger of splitting).
I see that where CJs are perpendicular to rafters, one can use strongbacks to tie CJs to rafters. Again 3x16d connecting strongbacks to rafters, each strongback must connect with at least 4 CJs via 2x16d nails. I am wondering if one could put blocking between the CJs, a brace connected by 3x16d to the rafter, connected by something like a H10 to the blocking. The trick would be to fasten the blocking to support the strongback, I ain't putting 4 pieces of blocking per joist bay!
I can see the pickle you're in now. Hurricane ties not made to handle the rafter thrust. I didn't know the rafters weren't along side the joists.
Any chance you can get into the attic and just add rafter ties?
Where I am, code gives three choices (for non-bearing ridge):
1. rafter ties,
2. CJ's act as rafter ties,
3. rafters connected to the deck if the joists run perpendicular. Then there's a whole section on what the deck is made of if you do it that way.
Almost forgot, also definitely call Simpson. Free engineering 'cause they want to sell their product. The answer might be "no, you can't do that" but you never know. As yet another way to skin a cat, they sell a metal bracing in rolls that you can easily carry up into the attic and it will very likely take the tension as would a rafter tie. They can tell you if that would work.
"Let's get crack-a-lackin" --- Adam Carolla
Edited 4/23/2006 3:09 pm ET by philarenewal
I discussed rafter ties with DW last night. We agreed that we'd prefer to stay married.The problem is it's a walk-up attic with T&G flooring used for storage. Even if I ripped up the flooring to put down rafter ties, I'd have to deal with midspan blocking, wires, recessed lights, AC registers, etc. Putting a second floor over rafter ties is inadvisable, the joists are only 2x6 with free spans of about 12'.Doncha luv these old houses?At this point I'm thinking some hack with a 2x4 brace, blocking, a H10 and 3x16d into the rafter may be the least worst solution. 3x16d gives about 400lbs of shear strength, the H10 is well over 500lbs in the F2 (perpendicular to top plate) direction. All I need is something to fasten the H10 to. Think like a joist, except the force is going horizontally rather than vertically. 2x4 ledgers on their side in the joist bay, fastened by 3x10d nails, then a doubled-up 2x4 on its side toe-nailed to the ledgers and the joists, then H10 and brace.... All I have to do is check my sanity at the door.....Edit: Thanks, I will talk to Simpson. I almost know all their tech people on a first name basis at this point :-).
Edited 4/23/2006 3:23 pm ET by Taylor