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-   -   Garage Ceiling Insulation Help (http://www.diychatroom.com/f19/garage-ceiling-insulation-help-64244/)

PyroG 02-12-2010 10:39 AM

Garage Ceiling Insulation Help
 
Hello.

I'm pretty new concerning a lot of this stuff and was wondering if maybe I can get a little help. Thank you in advance.

I would like to insulate my attached 1 car garage. It is 25' long and 11' wide.

The ceiling joists are running the long way at 32" oc using 2x6's. There are a couple 2x4 running the width as support under these joists (tho there is considerable sag on the middle 2x4 where the joist beams are connected.

I'm not sure if these joist would be strong enough to support any amount of drywall, even with adding supports between the joists.

now if there is any informative reads you can point me in for this or any suggestions it would be greatly appreciated.

I was thinking. adding more joists to split the differences making them 16" oc. tho this will put more strain on that single 2x4 in the center of the room.

I could run "joists" under the current struture going the other way using joist hangers on the wall studs (have plenty of ceiling room) . this would lessen the strain of the weight on the wood and let the current joists rest in piece. - for 11' would i go 16" oc or would 32" oc be ok for this? (cost reasons)

Or any other suggestion. like i said, i have the know how to carry it out, but i'm lost on which way i should go which would be considered "correct"

Any help would be great.

Thank you,

Matt W

Ron6519 02-12-2010 10:54 AM

The garage is severely under structured. You can't have 2x6's running 25 feet, 32" oc, with just 2x4's running 11 feet under them. I would run, 3, double 2x8's under the 2x6's to replace the 2x4's. I would place them so the space was divided into quarters , so the maximum span of the 2x6's were under 7 feet. If you want to hang drywall, add 2x'6s so the framing was 16 oc, not 32.
Insulate the ceiling, not the roof rafters.
Post some pictures of the structure as there are probably other deficiencies in the framing.
Ron

PyroG 02-12-2010 06:56 PM

6 Attachment(s)
I attached some photos. I'll see if I can get any better images. The lady who lived here before me had some pieces of plywood up in the joists where she stored some stuff, but I currently don't have anything up there.

Thank you very much for the help.

Ron6519 02-12-2010 07:58 PM

Pictures make it worse as the 2x4's are on the flats. The 2x6's were designed to hold the walls of the garage together, not to be used for flooring. If you want to hang drywall and insulate and hold the walls together, you'll need to redesign the floor structure.
Ron

Wildie 02-12-2010 08:22 PM

Those 2X6's are what are called 'collar ties'! They keep the walls from being pushed out by the weight on the roof rafters! They are not put in place to carry a load.
I would install ledger boards on each of the side walls and run 2X6 ceiling joists across the 11' span. These would be installed on 16" centers and mounted on the ledger boards using joist hangers.
This would be capable of supporting the insulation and the drywall. But, would not be suitable for walking on!

Gary in WA 02-12-2010 09:08 PM

Mud the wire holes and framing 2x4 holes in the firewall at the house. Also paper tape and coat over the seams and nail heads of drywall above ceiling (painted) line to isolate any fire in the garage from entering the house attic as per code (required).

Run 2x6s across the short (11) span below the existing at 16 or 32 on center, depending on the ceiling material. Drywall needs 16o.c. or 24o.c. to support insulation. Certain plywood sheathing is rated for 32o.c.(label on the wood).

2x6 Hem/fir at 1150fb spanning 11 will carry 527# total load. 48# -10# dead load = 38# / 2.67 (32o.c.) = 14# live load. 38# / 1.34 (16o.c.) = 28# per square foot.

2x6 Doug/fir at 1650fb spanning 11 will carry 664# total load. 60# -10# d.l. = 50# / 2.67 (32o.c.) = 19# live load. 50# / 1.34 (16o.c.) = 37# live load.

Drywall (1/2) weighs 2.2# per sq. ft. 5/8 = 2.75#. Glass batt insulation is 0.04# per inch per square foot. (Multiply by on center spacing). Cellulose is 0.14# per sq ft.

ply or OSB = 1.4 1.7# per sq. ft. ply or OSB = 2.2 2.5# per sq. ft.

Crunch the cost numbers for your budget. The plywood would also act as a vapor barrier; remember to ventilate the garage attic.

Be safe, Gary

wnabcptrNH 02-13-2010 07:48 AM

Quote:

Originally Posted by Wildie (Post 398893)
Those 2X6's are what are called 'collar ties'! They keep the walls from being pushed out by the weight on the roof rafters! They are not put in place to carry a load.
I would install ledger boards on each of the side walls and run 2X6 ceiling joists across the 11' span. These would be installed on 16" centers and mounted on the ledger boards using joist hangers.
This would be capable of supporting the insulation and the drywall. But, would not be suitable for walking on!


In canada it may be different but in the state those are not collar ties. Those are ceiling joists. Collar ties are attached the just the rafters further up to help with sag. Ceiling joists sit on top of your top plate and hold the outside wall in.

IMHO i would remove all those existing 2x (one at a time that is and put up 2x10 @16 OC at every rafter. Then strap your ceiling and install insualtion and drywall.

Scuba_Dave 02-13-2010 09:15 AM

IF ceiling joist are run the short distance...
THEN
I'm thinking the existing 2x's need to remain to hold the walls in against the push of the rafters ?

Ron6519 02-13-2010 09:45 AM

I would triple up the joists on either ends, 2 feet from the rafter tails and install outriggers to each rafter. Add hurricane ties to the rafter tails and bolt the outriggers to each rafter. This way the walls are tied in and you have an open space above for storage.
Ron

PyroG 02-13-2010 11:32 AM

thank you for all the feedback. i'm getting a much better idea of what i'm going to need to do.

One other question. If I want to expand up (currently we own a 1 story ranch) and add a second floor. Will there be any issues in the future with any of the suggested routes?

Thank you again.

Gary in WA 02-13-2010 11:35 AM

Rafter ties must be near the plates to be effective

http://myconco.com/pics/rafterties.jpg Many builders confuse collar ties with rafter ties. Both are horizontal framing members that connect rafters, but that's where the similarities end. Collar ties (which are required by the Southern Building Code and no other) function to resist the pressures of wind uplift on a roof by holding the rafters together where they meet the ridge. As high up as they are, collar ties have no leverage to prevent the rafters and walls from spreading outward. That job is best done by the ceiling joists. The wrong and the rights of rafter tiesTo prevent roof loads from spreading the walls outward, rafter ties (or ceiling joists) must be in the lower third of the roof pitch. Collar ties are too high to keep walls from spreading and instead serve to resist uplift by holding the rafter together at the ridge.
If there are no ceiling joists or if the joists run perpendicular to the rafters, then the code requires rafter ties. Similar to a ceiling joist, a rafter tie is typically a 2x4 that runs parallel to the rafters, from outside wall to outside wall, and ties the rafters together as close to the top plate as possible. Rafter ties need to be installed every 4 ft. down the length of the roof.
Rafter ties do not have to be at ceiling height to be effective, but they must not be placed any higher than the lower third of the roof pitch. In other words: Measure vertically from the outside wall's top plate to the bottom of the ridge, and place the rafter ties within the lower third of that measurement. Once they get above that point, they lose their most effective leverage. From: http://myconco.com/ComEngProb.html


Just install another ceiling below, as I mentioned: "Run 2x6’s across the short (11’) span below the existing at 16” or 32” on center".



Or, better yet, just add 2x8's as Ron said in the first reply, a lot less lumber than the other options.



Be safe, Gary

Wildie 02-13-2010 12:02 PM

The names used must be a regional thing! In my area the collar is considered to be at the sill plate!
They are used to prevent outward movement of the walls from the pressure exerted from the rafters.
Rafter ties are considered as those members that pull the rafters together and are usually positioned in the top 1/3 of the roof structure!

Gary in WA 02-13-2010 01:41 PM

We are backwards and a day late! lol.....
Be safe, Gary

Ron6519 02-13-2010 01:54 PM

Quote:

Originally Posted by PyroG (Post 399171)
thank you for all the feedback. i'm getting a much better idea of what i'm going to need to do.

One other question. If I want to expand up (currently we own a 1 story ranch) and add a second floor. Will there be any issues in the future with any of the suggested routes?

Thank you again.

There are no, "all purpose" solutions. These are solutions for sheetrock, insulation and storage. Living space criteria is controlled by the local building codes. If you're thinking of converting it to living space, contact someone who can draw plans for the "eventuality" and build the floor to that spec.
You might need a permit and inspection to make sure you did it correctly.
Ron

PyroG 02-16-2010 09:17 AM

Thank you everyone for the input. I believe i have a good game plan and am moving forward. I'm planning on only keeping it as a garage, so I don't need to go thru with all the permits and everything. just want to have a warm space to do work and workout.

Thanks Again,

Matt W


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