Framing Ceiling Joists

[spebby_92]

I am building an attached garage to replace an attached carport. The existing carport had a flat roof. The new garage will tie into the house's roof with the same slope, 3:12. Although the house has a hip roof, the roof over the garage will be a gable roof. The garage is approx. 25' x 31'. The ceiling joist will run perpendicular to the rafters . The 25' span of the ceiling joist requires either 2 x 10's or 2 x 12, depending on whats available at the lumber yard. With the shallow slope of the roof, the first joist will be approx. 4' from the parallel exterior wall. I plan on adding joists perpendicular to the ceiling joists to the exterior wall. I will use joist hangers for the connection at the ceiling joist. My question: Is a 4' perpendicular joist too long? I assume I will need to add blocking to attach the sheetrock. Will the above pass an inspection (IRC 2003)? I will be adding stongbacks at 4' o.c. since the ceiling joists run perpendicular to the rafters.

[DanG]

How are you planning to hold the outside walls if the clng joists are not parallel to the roof rafters? The triangle created by rafters and joists is crucial to the structure.

It is possible to create a structural ridge, but this is not usual and requires some careful planning.

[spebby_92]

The span is approx. 31' if I run the the joists parallel to the rafters and the angle cut on the joists would be serve due to the shallow slope of the roof. I intend to run the strongback from rafter to rafter 4' o.c. The strongback would be the base of the triangle.

[v8z]

Why not take / fax a drawing to a truss company. At that low a pitch there isn't going to be any usable "attic" space, and overall manufactured trusses would probably be more cost effective than the large dimesional joists. Plus, the truss company will do the engineering for you. Only thing you'd have to stick would be the hip/gable overbuild ( if I interpreted your description correctly)

[Glenn]

If I understand your description, yes it would work but with some modifications.

You won't get a ceiling joist 2 x 10 or 2 x 12 within

16" of the wall under a 3/12 roof rafter so I would put solid bridging every 4' as you want from that joist that *will* go under the rafter and block in between the 4' bridging with the extra edge joist of 1 x 4 or 2 x 6. The 4' stiff backs nailed well to the rafter and bridging would do the job fine. Then double up the extra loaded joist.

[RicodJour]

No one can answer that question. Sizing the members is only part of the solution. The connections are just as important, and your version has some serious limitations.

I don't understand what you're trying to do with the whole setup. You should price your idea against trusses. You might be surprised how little difference there will be in cost and your way is a lot more work.

R

[spebby_92]

I really appreciate the responses. I will check into trusses. One problem with trusses is access for a crane to lift the trusses. The power line drop is in the way of the ideal location for the crane. In fact the electric meter will need to be moved at some point in the project otherwise the meter will be inside the garage. But I need a wall and the roof in place before it can be moved.

I can size the members without problem, I have the span tables and know the loads required by the city. I will try to explain the question another way assuming trusses do not work out. The house is basically a rectangle with a hip roof with a 3:12 slope with 4' eave overhangs. The shallow roof slope means a 2 x 10 joist will be more than 16" from the exterior wall. Using a 2 x 10, the outside joist will be a little over 3' from the exterior wall. I will call the 2 x

10 joist a "regular" joist. The plan is to place a "short" joist perpendicular to the "regular" joist that extends to the exterior wall. The "short" joists will have blocking between them at the exterior wall to provide a way to attach the sheetrock ceiling. My question: The "short" joist will be a little over 3' in length, is there anything in the framing code placing a limit on the length of a "short" joist?

I will post the difference in cost when I get a price for the trusses. If it's like everything else in this project, the cost of trusses will be out of sight. I received two bids on this garage from remodeling contractors, one for $90,000 and one for $55,000. Doing the job myself, the cost is about $18,000.

[marson]

Well, to answer your question, a joist is a joist. If you know the span, then you can figure out the rest. I would be more concerned about overloading the joist that the blocking is tying into. You say you want to span 25'? Are you serious? First of all, where are you going to get lumber over 25'? If your ceiling joists are only functioning to hold up a drywall ceiling, I would suggest a suspended drywall ceiling by USG. That said, you should look into trusses.

[spebby_92]

Marson, I checked with my lumber yard and 2 x 12 x 26' are available (Douglas Fir). Normally 2 x 10 x 26' are in stock, but the day I called they were out. With no attic storage, and a sheetrock ceiling, either will work according to the span tables. The 2 x 12 can span

31'. I do intend to check on trusses and will go that route if they are affordable. The 2 x 12s are affordable but are more work as mentioned by an earlier poster. Walking through a number of houses under construction in my area, a 25' span or greater is common in the garage area with some using 2 x 10 , some using 2 x 12 and some using engineered joists. I have seen several things that I didn't think were to code (for example a purlin supported by double joist spanning 25' instead of a load bearing wall) but the inspection sticker was present.

[marson]

OK, I didn't know that. Here in the midwest, long lengths like that are special order. You might want to double the last joist, the one that has the blocking tied to it, since that joist is carrying more load than the others.

[spebby_92]

quoted text -

Thanks marson, if I go the non-truss route I will double the last joist.

[Glenn]

I of course, meant 2 x 4 and not 1 x 4, either parallel to the joist or perpendicular like the solid bridging.

I am wasting you 2 joists though by saying double the joist at the edge with the blocking. It's supported every 4' with stiff backs bearing directly on the solid bridging that is in turn bearing on the outside plate and as such is probably the strongest one in the ceiling.