Garage Truss rebuild

[psadler]

Greetings All, As you can see from the photo the original truss system was removed from my 65 year old garage by previous owners. I want to rebuild a truss support. The span for the joist is 18 feet. From what I can read on various span tables 2x6x18 Douglas fir is within tolerance. I don't have issues of snow and the roof is composite shingle. Question I have in getting started is how to attach the joist to the wall/rafter.

Support bracket that attach the joist to the bottom of the rafters and the side of the wall plate? What length screws 2"?
Or
Fitted on top of the wall plate and attached to the side of the rafter? Lag bolts to connect the joist to the rafter? If I do that then I can't line up struts to connect to the rafter above? did I just answer my own question?

Any thoughts or tips are appreciated.

Thanks, Philip

 

[BillK]

As you can see from the photo the original truss system was removed from my 65 year old garage

Not sure what you mean by this. I would bet that the roof is exactly the way it was built 65 years ago. "Trusses" were almost unheard of back then. It does look like it could use some more collar ties ?

 

[nanan00]

Yep, that is just about what my aunts 1910's built house looks like in the attic, it had glass knob electrical insulators and bare wires strung up all over the place...

 

[Zeke]

Are you wanting a finished ceiling? You need more than 2 x 6. Anyway, cut the new joists just short enough to fit in the cavities between the rafters, pull them to center resting on both plates and secure to the sides of the rafters. If ties, raise them up as far as 1/3 the way up the rafter. You need to tie the other 2 walls as well. Lots of Google images of a full hip roof which is what you have.

 

[wssix99]

Are you looking to create a flat ceiling here? Personally, I think keeping the profile of the rafters would give you a cool garage/temple look.

Or, are you after another level for storage? If so, you'd probably need to have some engineering done and reinforce the walls. (They do not look like they were built for that kind of loading.)

 

[JoeFin]

My garage was built in 57 and used rafters with "Collar Ties" and "Rafter Ties" and by today's standards a way over spanned "Purlin" beam. The purlin beam was cracked and sagging, the rafter ties were scabbed together and some previous owner had tried to use them for storage.

Me and my wife, (who happens to be an architect), designed a truss system, then used 2"x4"s to prop up the sagging roof to its original slope and them supported them with the trusses.

No we didn't have to. We could have returned it to original spec and it probably would have lasted another 50 years as the original one did. But by doing so I gained a 5/8" rock ceiling, a storage loft with loft ladder installed, and a fully insulated garage which is much easier to heat in the winter and cool in the summer.

 

[psadler]

BillK, I was wondering why I couldn't see where I had thought the originial joist would be attached. I didn't think that it would have been built without truss system. Thanks Zeke for the descriptors, I'll be sure to tie in the other walls if I create the truss. There is no sagging, so that's not an issue. I do not want a finished ceiling. Maybe some better placed collar ties would be sufficient? I will be installing a roll up garage door. Current plan is to insulate the walls and ceiling, rolling out fiberglass faced. That has a particular look, so maybe just a radiant barrier. I too like the open "cathedral" ceiling. I'm interested in a slat wall system for two walls, but the ceiling I do not intend to drywall. I have a lot of other issues with this garage that I will be checking in with you all.Thanks. ps

 

[kbs2244]

If you are going to a new door think about having the tracks follow the roof slope.
You will be able to keep all that interior space.

 

[wssix99]

BillK, I was wondering why I couldn't see where I had thought the originial joist would be attached.

Think of your roof like a dome. It's engineered very similarly, so there never would have been any cross members. The weight of the roof presses down on the center and bears on the tops of the walls. There might be a little force pressing the walls away from each other, but since you don't have snow loads, that shouldn't be a heavy loading.

I too like the open "cathedral" ceiling. I'm interested in a slat wall system for two walls, but the ceiling I do not intend to drywall.

If you like it open and are not drywalling, what would you need the "truss" for? Were you thinking that you needed it for the structure?

 

[gungatim]

those are not trusses, they are rafters. big difference in how they are designed and support the load.

 

[jkwilson]

Been a lot of repair on that building. Most of the studs and some rafters are new.

 

[psadler]

The garage is on a slab that allowed water to seep thru and create a lot of dry rot and some termite damage. Also the windows that were on the wall with all the new studs leaked quite a bit over time.

 

[Chris705]

My $.02

2x6's as rafter ties with midspan support coming down from near the ridge would go a long way to prevent eventual splaying of the walls. 2x4's would also work if you can purchase them long enough. The vertical support will prevent sag. Fastening to the rafters w/ 3" structural screws and also using hurricane hold down clips is what I would do. I do question the overall dimensions of the garage? The photo almost makes it look square? THis is very similar to another post where the poster wanted to remove what he thought was a strong back running over the top of the ceiling joists (rafter ties). I would then recommend running one or two equally spaced rafter ties over the top of the first (perpendicular) to connect the rafters running the other way.

 

[psadler]

thanks Chris705. The garage is almost square at 18'x19'. I'm thinking using 2x4 so as to not add so much weight to the structure. I need stability versus vertical storage. Can the perpendicular rafter ties just attach to the side of the ceiling joist versus lay on top and span the entire width?

 

[Chris705]

You really want it to act as a tension member resisting the outward horizontal thrust the rafters put on that wall so I'd try to run continuously. A long nailed overlap of shorter members would be ok. Again I think at most there only needs ties at 4' on the long walls and maybe break the shorter span into thirds with two members.