changing truss roof to stick framing?
Dear breaktimers,
I am a painter, carpenter, handyman in a smalltown and generally stick to small projects. but I have a customer that wants me to make the attic area over their garage usable for storage and eventually an extra room. The problem is that it is truss construction. For the floor I plan to use 11 7/8 I-joists 12″ o/c under the existing trusses. (the span is 22′) My question is can I sister boards to the top chord of the trusses and add collar ties so that I can cut out the upright members so there can be more usable space?
thanks, the home craftsman
Replies
The truss is an engineered member. No tradesman can accurately answer that question, without a truss engineer's assessment. Since you are adding a 2nd floor, you will need a structural engineer's evaluation of the existing structure and footings. This would be the time to discuss the elimination of the roof trusses to add your 2nd floor above the garage.
My guess would be to take them out completely, to add your new framing. But if the shell is exactly as you want to keep it, you might end up building around the trusses, then eliminating the webbing. But doing so violates the integrity of the trusses so thoroughly that you are in essence removing the trusses completely, from a structural standpoint, by doing so.
"he...never charged nothing for his preaching, and it was worth it, too" - Mark Twain
Hi HUck,
Thanks for the advice, I am getting help from a truss engineer.
the home craftsman
yes, you sure can.... i'd get a sit-down with the building inspector to make sure it's going to fly.. and check the span tables on your I-joists..
and the design load ( 30 lb / 40 lb ) or look for point loads
also a problem will be access ... you'll probably need a stairwell at some point
in the end the trusses are going to be just something that is holding the plywood sheathing in place temporarily..
also.. it may in fact be cheaper to rip the roof and start over .. you're going to be fighting this from the get-go
That was my first thought.... it'll be harder to do with the trusses in the way. Just demo them and frame a new roof. I'm sure the objection will be exposure to the weather.
thanks Mike for your advice. I am going to get some help from an engineer.
the home craftsman
First - 12" I-joists won't span 22' in this situation. Check the manufacturerr's specs for I-joists used for bonus rooms and you'll see that they'll call out deeper members.
As for the rest of the structure, it will work fine as long as the whole system is designed by an engineer. Just nailing boards alongside truss top chords isn't likely to be enough.
Like Mike Smith said, it may be better to tear off the whole thing and start over.
Divorced
Mike and Boss is right.
Just sawzall the roof free at the plate line. Set it aside with the crane. Add your new room with floor trusses and reset the same roof.
blue
You may want to check with an engineer to see if the foundation will support the added floor. Otherwise, this is a common method to add a room.
Not knowing the exact situation. I have seen it where a single story building was jacked up and a set of studs with floor joists on top was put underneath the existing building to make an additional floor.