View Full Version : Roof Framing Options


central1ny
08-31-2011, 12:02 PM
Anyone here frame their own roof for a 24 foot or wider garage? I like the idea of framing my garage roof instead of trusses simply for the storage space. The garage is 24 feet wide and would like the ceiling joists to clear span this distance without a center support. This is where I am running into problems. Has anyone done this and if so, how?

Per NYS building code (http://publicecodes.citation.com/st/ny/st/b400v10/st_ny_st_b400v10_8_sec002_par017.htm), it looks like 2x10 spruce-pine-fir would work for a dead load of 5 psf but not for a dead load of 10 psf.

I did a rough calculation of dead load taking into account the weight of the 2x8 lumber for the joist, the sheetrock for the ceiling, and plywood for storage space decking and estimate a dead load of ~ 6 psf, does this sound right?

twostory
08-31-2011, 12:23 PM
I stick built a my garage addition. 22ft deep x 30ft wide. I used a big LVL beam (22ft) for the ridge, supported on both ends. Then used 2x8x(15+) for the roof rafters (30ft wide). I used metal hangers for the roof rafter at the LVL beam. Then just cut birds mouths were the rafter meet the side walls.

The LVL are not too expensive and a benefit is a strong ridge beam down the middle of my garage to pick things up with (using a chain hoist)

slowthump
08-31-2011, 12:39 PM
I just got done framing my 30 x 40 garage. I split the 40 foot length into a a heated 16X30 section and a 24X30 non heated space. For the heated area I used 2.5" x 12" x 16' I-joists for ceiling joists. I used 2.5" x 12" x 18' I-joists for roof rafters with a 14" deep 20' lvl ridge board.

The cost of framing ceiling and roof with I-joists was about exactly the same as using standard trusses. But with the I-joists, I end up with great loft storage, more space in ceiling to insulate and much higher load factor. For the life of me I can't figure out why anybody would use those special made trusses for adding a loft/storage area. Those are way more money than framing with I-joists for less load. Granted, there is a whole lot more time and labor involved with hand framing it all.

If you look up one of the I-joist manufacturers (trussjoist, nordic)they have span tables and I know the make products that easily span 24'.

rieferman
08-31-2011, 01:39 PM
For the life of me I can't figure out why anybody would use those special made trusses for adding a loft/storage area. Those are way more money than framing with I-joists for less load. Granted, there is a whole lot more time and labor involved with hand framing it all.

I believe that's the answer. An attic/storage truss has the benefit of being very fast to install.

Falcon67
08-31-2011, 01:47 PM
Doing it right now:
http://raceabilene.com/misc/NewShop/Framing19.jpg
24' wide. The joists are 2x12x24 because I would have had to buy 40 2x10s from McCoy's warehouse - just not stocked around here. I'm using a 5/12 pitch so I can rafter with a 2x6x14. Rafter length is 13' 10 9/16". It's all 24' OC. Total cost to frame the roof including the fly rafters and 2x6s for boxing the ends of the rafter tails (soffit) comes to right at $1000. The 2x8 ridge was "free" because of left over lumber from the neighbors driveway pour. Now - I can't go buy a 24' 2x10 but I scored a free 28' 2x8 from next door. WTF.

Just for fun, I can tell you that on my last shop I used 2x6x20 for the joists. I either mis-read the span tables, or something. Anyway, I had 128 sq/ft of storage up there (64 on either end) and it was loaded up. The joists sagged about 1" over 12 years but never gave me any trouble.

central1ny
08-31-2011, 03:26 PM
Doing it right now:
24' wide. The joists are 2x12x24 because I would have had to buy 40 2x10s from McCoy's warehouse - just not stocked around here. I'm using a 5/12 pitch so I can rafter with a 2x6x14. Rafter length is 13' 10 9/16". It's all 24' OC. Total cost to frame the roof including the fly rafters and 2x6s for boxing the ends of the rafter tails (soffit) comes to right at $1000. The 2x8 ridge was "free" because of left over lumber from the neighbors driveway pour. Now - I can't go buy a 24' 2x10 but I scored a free 28' 2x8 from next door. WTF.


I just got off the horn with the codes guy and he is going to allow 2x10 for the joists but I may go with 2x12 just to overbuild a little. I need to go with 2x8 for the rafters because I am in snow country so I will need a 2x10 for a ridge board. I am going with 16" OC. I think this is the way I will go instead of trusses. I like the idea of having some storage space.

K'ledgeBldr
08-31-2011, 05:24 PM
I'm betting the only way he's allowing it is with a scuttle hole service- no pulldown stairs.
I'd like to see the price of 2X10/2X12 in a 26' length- Holy S#!T my wallet's on fire!
I'd find a local truss manufacturer and have them engineer trusses with "Attic room".
There are all kinds of trusses-
from simple king post to modified queen, to triple fink, and triple howe.
And then there are more complicated trusses like cathedral, coffer, vault, and attic room. And some can be clear span to 80'. And much less money than stick framing- labor and material.

But, I also like slowthump's idea- Ijoist. With those you can design actual living area (30 live load).

hockey88fan
08-31-2011, 07:29 PM
These are the trusses I'm going with but mine spans 29'. I had a local truss company make these for $195 a piece. The live load is 50lbs the dead load is 15, they're being placed on 16" centers.

http://bradleybuildings.com/cambridgemax.htm

central1ny
08-31-2011, 07:37 PM
I'm betting the only way he's allowing it is with a scuttle hole service- no pulldown stairs.
I'd like to see the price of 2X10/2X12 in a 26' length- Holy S#!T my wallet's on fire!.


I already checked with the truss manufacturer and they told me it was a waste of time to get an attic truss for a 5/12 pitch as there would not be enough usable space. I got a price of $38.84 for a 2x12x24' today. I also got a price for a wooden I beam for the same length and the price was $62.50. Conventional framing is far cheaper than using the wood I beam as far as I can tell.

As far as span ratings, I was a little suprised. Per NYS building code, a 2x10 has a tough time spaning 24 feet at 16" OC. unless you use SS southern yellow pine. And for some reason, the NYS building code does not even identify 2x12 as an option for joists.

hockey88fan
08-31-2011, 08:23 PM
I already checked with the truss manufacturer and they told me it was a waste of time to get an attic truss for a 5/12 pitch as there would not be enough usable space. I got a price of $38.84 for a 2x12x24' today. I also got a price for a wooden I beam for the same length and the price was $62.50. Conventional framing is far cheaper than using the wood I beam as far as I can tell.

As far as span ratings, I was a little suprised. Per NYS building code, a 2x10 has a tough time spaning 24 feet at 16" OC. unless you use SS southern yellow pine. And for some reason, the NYS building code does not even identify 2x12 as an option for joists.

With the truss I'm using you'd get a 20' room

dlc
08-31-2011, 09:18 PM
My garage is 24x32 and I used "room in attic" 2x10 trusses. The pitch is 10/12 and I have a room 32' long, 12' wide and over 8' tall. They were really heavy and had to be placed with a boom truck.

http://supratrucks.com/pictures/Garage/New%20Garage/Day%20five%20001a.jpg

http://supratrucks.com/pictures/Garage/New%20Garage/attic1.JPG

http://supratrucks.com/pictures/Garage/New%20Garage/doors%20001a.jpg

Falcon67
08-31-2011, 10:56 PM
I paid $28 each for my 2x12x24' joists. Total works out to $44 or so every 2'. As noted, what you save in $ you will spend big in time. The 12s are a bitch to set - about 100 lbs each. And they are not all exactly straight or 11 1/4" wide as you might think a beefy tostada board like that might be LOL. Ah, drywall has some give to it. They sure don't flex when I walk across them though. I'll end up storing more over the work area than I thought just because I have killer joists. And some OSB up there helps keep them in line and not laying over.

I'm OK with the 2x6x14 since there is no snow load here. I'm still putting in some strongbacks under the rafters. They'll help keep things close to 24" OC anyway.

If I had gone wider - like 26 or 28', I would have gone to a truss for speed and span.

TWX
09-01-2011, 12:15 AM
My flat-roof garage has 28' long 2x12s for joists, 24' over the interior of the workshop, then on the cinderblock wall, then a little over 3' overhanging the outside back. I can't remember the distance apart. It's more than strong enough for when my dad and I were up there inspecting the place after I bought it. The roofing material is probably 3/4" plywood with a thick layer of foam and a sealant. Inside there are at least two sets of boards perpendicular, bridging the gap between the 2x12s.

I'd bet that the 28' boards were special order, I've never, ever seen 2x12s in that length anywhere else.

Falcon67
09-01-2011, 08:21 AM
Here's a pic of 5/12 pitch attic space FWIW:

Rosco
09-01-2011, 09:37 AM
My garage is 26 X 30. I have a 11/12 pitch roof which gave me enough room for a 18' wide bonus room upstairs (roughly 42" knee wall). The cieling in the bonus room is 8' tall (finished) by 8' wide before sloping.

I used 2 - 26' gluelam beams across the width (8' apart centered) and 2 X 12 floor joist in between. The gluelam beams are directly under the walls for my upstairs dormers, which are 8' wide. I floored the entire upstairs with 3/4 T&G prior to raising the rafters. Everything is on 16" centers and rafters are 2 X 8.

After all was said and done I have almost the same amount of money invested, more labor, but a lot bigger bonus room and a very sturdy floor.

Upstairs is now sheetrocked/mudded, has a full bath in one of the dormers and a walk-in closet in the other.

Good luck on whatever you decide!

central1ny
09-01-2011, 03:35 PM
Here's a pic of 5/12 pitch attic space FWIW:

Are you planning on putting any cross-bracing on?

Falcon67
09-01-2011, 04:59 PM
Are you planning on putting any cross-bracing on?

You mean collar ties? About every 4th will get a short 2x4 after all the rafters are in. That really doesn't do much of anything though - the rafters ride against the ridge and the plate, collar ties won't stop them from coming apart should either of those items suffer a catastrophic defect. The seats of the rafters will get hurricane ties (Simpson H1) and the joists all get ties at the top plate. Just because.