Going from a Common Rafter to a Scissor
Ok did some searching with a bit of help, but looking for some more. My case is very similar to this post:http://forums.taunton.com/n/mb/message.asp?webtag=tp-breaktime&msg=70882.1&maxT=7
Have a 1977 ranch with 8′ ceilings and a 5/12 roof trusses which the exterior walls 30′. We want to do a cathedral ceiling over the entry and family room which is about 25′ in length. Since the existing trusses run the correct way I thought easiest would be to pop out the ten or so trusses and replace with a scissors truss. Ha ha , anyway could a scissors truss be made in place from the existing truss? Then would it pass building code? Seems like it would be tough to get the bottom cord in place for the seat cut to sit on the top plate. Then get everything tied together with nail plates or plywood. We plan on re-roofing so that makes things a bit better, but tearing out and replacing plywood etc., well you get the idea. It always sounds easy ” sure we could just raise the ceiling”. So anyone we some insight here would be greatly appreciated.
Thanks Jeff
Replies
Jeff,
We have popped up into trussed ceilings before. What we do is build a structural ridge that will sit beneath the new rafters (sized appropriately for structural and insulation needs) The new rafters get sistered to the top chord of the truss with a birdsmouth cut out at top to rest on the structural ridge and cut to fit at the wall as well. We use LVLs because you get more strength than dimensional lumber. Once everything is attached, and the ridge is supported on both ends, we simply cut the bottom chord of the truss out.
You can do this without removing the roof and with minimal damage to interior walls. The only hole we needed to make was to install studs to the slab for bearing of the ridge.
All this was coordinated with a structural engineer and alot of temporary bracing. First truss cut had a lot of pucker factor, but all went well. I would post a picture but my skill set is limited when it comes to that kind of stuff.
Bruce
Your best advice to consult a structural engineer is priceless.
To modify trusses in place and have it pass code you'll need an engineers stamp. This may not be as expensive as it sounds. One local truss company has a guy who loves working out problems like this and he'll come out look at what you have, run the numbers and draw a set of detailed plans for the fix. It usually involves careful cuts, reinforcement with plywood at joints/intersections, and a lot of cinched nails.
Beer was created so carpenters wouldn't rule the world.
I don't think this will work with scissors trusses. If you possibly could the inside pitch would be a 1/12 maybe 2/12, hardly worth the work for that small of a cathedral.
Your problem is more than likely going to be a small heel height, right now you have a 2x4 on a 5/12 pitch. Maybe 3-3/4"or 4", not enough room to get a scissored bottom chord and top chord in together and have the room plane together flat.
The lowest pitched roof I have used scissor trusses on was an 8/12.
Just take the old trusses out and rafter the area you want.
Bosshog designs trusses maybe he will be along to tell me I am full of sh!t, and they make something for your situation.
Stilletto, you aren't full of it, but you should remember this adage "Where there's a will, there's a way."
Creating those trusses is just another day at the truss company picnic.
blueOur Skytrak is for sale. It has 500 hrs on it. We want 50k (you pay the freight) and we'll finance it. Drop me an email; it's a good buy.
I am sure there is a way, I haven't encountered scissors with a small heel like he probably has. I think the smallest heel I have run into is 8-9".
Now that I think about it more a few ideas are popping into my head, but they involve more demo work than just the ceiling.
We've had to retrofit scissors when the builder forgot to order them correctly. It's a pain in the rear, but it certainly can be done. It's easier than ripping off the roof.
blue
Our Skytrak is for sale. It has 500 hrs on it. We want 50k (you pay the freight) and we'll finance it. Drop me an email; it's a good buy.