Re-insulating & Re-Finishing Garage

[Porcupine]

Hi Guys,

I currently have a 10x20 attached garage where the previous owner had insulated, vapour barriered and drywalled the interior.

The issue I run into is that everything in the garage runs on one breaker, and that includes exterior plug-ins on the house. The house was built 24 years ago. So, one thing I want to do is to run different electrical, add more plugins, etc, and I will have a company come in to do that work.

The other issue I have is the walls are drywalled. I have, by accident, dented and broken several areas of the drywall by leaning lawn and garden tools against it and general wear and tear. I would like to remove the drywall and replace it with plywood that will be more resilient. I have already called the city and have gotten the OK to do so, as long as the fire barrier remains on the wall with the house. I will remove that drywall to see what is exactly behind it, and I will use the proper 5x8 firecode drywall in its place and tape all the seams.

Since the garage is 2x4 construction, I want to build the walls out to 2x6 by adding 2x2 both nailed and glued to the existing 2x4's and increase the amount of insulation, including adding 2 inches of polystyrene foamboard on the cement foundation that the walls sit on (plywood will cover the foamboard). I figure if I am taking down the drywall, it would be worth doing since I will have full access to the wall cavities. Furthermore, it will be easier to run the electrical, as well as replacing some of the cable that comes into the garage going into the house (cable tv, etc). I already had to have a section of the cable replaced and a sizeable hole made in the wall because the previous home owner accidenty nailed through the outter jacketing of the cable, compromising its integrity. I do plan on tinkering in my garage in the winter months and have already done so. I have already replaced the garage door with an insulated steel door 1/3x4 thick, and have also changed the existing window. I also verified that the ceiling is insulated.

I guess my question(s) would be whether anyone as done any of the above, whether it is entirely worth doing, and if someone can offer some guidance, as I have not undertaken a project like this before. I understand that insulation should not be compressed, so I would be getting new insulation for the 2x6 studs (I will be reusing the fibreglass batting in my basement on the interior walls for soundproofing). I would then vapour barrier over it, tape all the seams, and then put plywood overtop, prime and paint with semi-gloss white.

Any tips/advice would be much appreciated - thank you in advance!

 

[NUTTSGT]

For a new I'd think about using 2x6 walls. I'm not sure that I would try to retrofit to deeper walls. Don't get me wrong, the more insulation, the better you are.

This would be the deciding factor for me. Are you going to maintain heat in the garage ?
If you are going to keep it heated all the time, I would add the depth to the wall. If you are only going to heat occassionally, I'd leave the 2x4 walls there and put R13 or R15 in.

Getting the concrete floor warm will be the biggest thing. For me, if my feet get cold, I'm done. I'd hate to make the garage some insulated but that cold floor wil **** the heat right out of it.

 

[Porcupine]

I would like to maintain heat in the garage, and I have read that some people have had success building out their existing walls to 2x6. Do you suggest that I just install 2x6 beside the existing 2x4, or are you saying that if it was a new build, then 2x6 would be the best route.

I am the same with the floor, that once my feet are cold, then it is miserable to be working outside, or anywhere for that matter. What could I do with the existing floor? The city forbids me to put any type of subfloor in my garage as they see it as turning the garage into a living space.

 

[NUTTSGT]

When I was talking new, I meant as in a new garage build, from scratch. It would be well worth the extra money to go with more wall/insulation, cheaper and easier to do it at that time.

Since you are maintaining the heat, by all means, go with the 2x6 walls and more insulation. I would probably scab them onto the front as that would be the easiest. Another possiblity, and hard work too, would be to cut out every other stud and replace it with a 2x6. The problem this creates is, you are unable to attach the exterior sheeting to the new studs unless you remove the siding.

In our front room, I remodelled it and it has hardwood floors under the carpet. After I ripped all the plaster and lathe off, the floor was 1 1/2" from the finished flooring. I ran 2x4s horizontally and used some white styrofoam inbetween them. I still nailed strips (vertically, between the horizontals) onto the studs and that where the outlet boxes are mounted to. I believe it still gave me an R19, as I used R13 in the walls.

 

[jonny o]

What about leaving the 2x4 and fiberglass after your rewire, then cover the studs with foam board before drywall/plywood?

Definitely easier in my mind, but you would have to run the cost per r value.

 

[Porcupine]

NUTTSGT - That would be possible on the one wall as it has vinyl sizing - the other is brickfaced. While we are planning on changing the siding, it won't happen for a few years - if we did, all I would do it put 1 inch foamboard and side overtop of that as I know some have done for an increased R-value of 5.

 

[Porcupine]

jonny o,

That sounds like a good alternative - Adding 2 inches of foamboard for an added R-10. I would have to remove the existing vapour barrier though right? Would I put new vapour barrier overtop of the foam? Would the plywood wall still be as strong (I would have to use longer screws to get into the studs)? I would still have to tape all of the seams of the foamboard?

Never thought about doing that - you've got the gears spinnin' now in my head. I wonder what the differences are aside from maybe cost, of doing one over the other.

 

[Painter123]

that sounds like a whole lot of extra work

Granted I'm in Vegas so keeping heat out is my main concern but....

I spray foamed both my attics, removed the sheet rock in my 3 car garage and spray foamed the walls that were not insolated

Now when it's 100+ outside the garage and the house stay around 75 with very minimal effort from the A/C

With all the extra costs of 2x2s, glue, 2" foam board, nails and what ever else you'll be needing plus all the extra work

you'll prolly break even cost wise just to use a couple of 600bf kits plus you'll save yourself a bunch of time and headeach and come out a head on the effencey side of it all

The spray foam is so easy to do yourself esp if your not crawling around on your stomach in a hot dusty nasty 25 yr old attic

 

[Gary S]

For a new I'd think about using 2x6 walls. I'm not sure that I would try to retrofit to deeper walls. Don't get me wrong, the more insulation, the better you are.

I agree. The 2x4 wall is adequate if you put R13 blankets in it. Remember that your weak point isn't a 2x4 wall, but the windows and doors. Very few garage doors are R13, and your average window is about R3 or less. Put your money there instead into a thicker wall.

 

[ChristopherLutz]

Painter...what's the R-value of the spray foam in a 2x4 cavity? (I'm sure there are several kinds of foam) I would think the spray foam would exceed R13....probably by a good measure.

If you're going to replace the drywall on the house side - take a look at sound insulating drywall - might be worth the extra few dollars.

incidentally, if you MAIN reason is to re-wire....you can do that w/o taking off ALL of the drywall and incurring that significant expense.

 

[shanker]

sound insulating drywall is more than just "a few dollars" extra though..

If anything, I'de throw 5/8's drywall up

 

[ddawg16]

The wall next to the house MUST be 5/8" drywall.....you can't use wood.

You can use OSB or plywood for the rest if you want......

Someone chime in....I believe that unless there is a smoke wall....the ceiling has to be drywall as well?

Anyway, like Gary said....most of your heat loss is through the garage door and windows....I thin you will be fine with R13.

Besides.....the garage is not that big....if you put in 2x6's....you are going to be loosing 4" of inside width....

 

[Painter123]

Painter...what's the R-value of the spray foam in a 2x4 cavity? (I'm sure there are several kinds of foam) I would think the spray foam would exceed R13....probably by a good measure.

If I remember correctly it's 6.0 per inch for closed cell
I sprayed the attics 5" thick and the walls are pretty much a 3" constent

Spray foam is really a lot more than just R-Value it's the total seal of the cavity

No drafts/heat/cool get in or out due to the way functions
something no other insolation can offer

 

[norcaljr]

If I remember correctly it's 6.0 per inch for closed cell
I sprayed the attics 5" thick and the walls are pretty much a 3" constent

Spray foam is really a lot more than just R-Value it's the total seal of the cavity

No drafts/heat/cool get in or out due to the way functions
something no other insolation can offer

Do you remember where you got your spray foam from ?

 

[Painter123]

Do you remember where you got your spray foam from ?

I bought 4 600bf kits from these guys

http://www.sprayfoamdirect.com/

then I found some guys selling it locally and bought 2 more from them

The prices were pretty much the same, shipping vs tax, but I didn't have to wait, that was pretty much the only reason I bought from a local company the second time

The stuffs not cheap though I can tell you that

 

[Daniel Dudley]

I have seen guys run 2x2 over the drywall, and run the wire at baseboard level and up to where they wanted it. They used to call this a Swedish wall, don't ask me why. If you ever want to upgrade the wire in the future, you can still access it by pulling the baseboard. I rarely demo stuff like insulation if I don't have to, same with drywall.

Sometimes it is easier, sometimes not.

 

[Thruxton]

I'm doing a project similar to yours right now, finishing an unfinished attached 20x20. Using 5/8 Type X on the house wall (code required), R13 FG in the frame walls (2x4 16OC), but slightly different wall treatment- 1/2 drywall over 3/8 plywood. Chose this after reading a lot here and elsewhere. Gives me a surface to paint high-gloss white that looks really good, plus the ability to screw light storage fixtures right onto the wall (heavier ones still go on the studs). So far I am really pleased with the results. Should note that this is multi-purpose space, woodworking, light machining, automotive.

 

[Porcupine]

I agree. The 2x4 wall is adequate if you put R13 blankets in it. Remember that your weak point isn't a 2x4 wall, but the windows and doors. Very few garage doors are R13, and your average window is about R3 or less. Put your money there instead into a thicker wall.

When I first moved in, I changed the existing wood garage door that was starting to rot at the bottom ends with a garaga steel insulated door, their highest rated insulated door. The existing garage window was changed to one with argon and low-e. Aside from those changes, nothing else has been done to improve the insulation.

If you're going to replace the drywall on the house side - take a look at sound insulating drywall - might be worth the extra few dollars.

incidentally, if you MAIN reason is to re-wire....you can do that w/o taking off ALL of the drywall and incurring that significant expense.

Will certainly take a look at some of that type of drywall. I don't think I have ever seen it before, but next time I venture out to HD I will take a look around.

The main reason for me taking down the drywall in the garage is that it is not durable. I do not want to always have to "patch" holes, dents, etc. I figured that if I was taking that down, then I would be able to get the electrical redone at the same time, as well as possibly increasing the insulation by building out the wall.

Besides.....the garage is not that big....if you put in 2x6's....you are going to be loosing 4" of inside width....

You bring up a very good point. The interior garage wall on the brickfaced side is flush with the concrete pad the walls sit on. If I add there, then I will certainly be reducing the width of the garage. There is about 2 to three inches on the other side where the the wall sits that I could build out so it would be flush with the concrete. But I gather from the posts made that the cost and effort involved would take a while to get recouped, leading me to believe it is not worth it.

Needless to say, I learned alot from the posts made here - I think I will still put up plywood on the two sidewalls and get the electrical upgraded.

 

[socapots]

didnt see it mentioned. but i did skim through.
something like 60% of heat loss is through the roof. Insulate the attic well. walls windows and doors are important.. but not as much as the attic.

 

[BLUBAYOU]

I agree on the overhead insulation. I'm not an expert, but I do know that you're going to get more bang for the buck insulating overhead than in the walls.

My first thought on your situation was blown cellulose or fiberglass. Leave the existing drywall up, blow the new insulation right up against the batts inside the walls and over the top of your attic insulation. It will just compress the existing batts in the walls and saves having to pull the drywall down. Throw your OSB/plywood right over the drywall. I would also consider running additional circuits via conduit outside the drywall. If done properly it can look good and gives you access to the wiring at any time in the future.

My new garage's walls are still open, but I plan on running some circuits in conduit outside the walls. There are 2 circuits for some outlets in the walls, but the compressor, welder, etc will be wired via conduit as I'm sure the layout will change over time.

Hope that helps,

Greg

 

[bczygan]

You can run wiring wherever you need with proper drills and fishing tools. Much of it will go overhead and fish down through wall cavities. No need to remove existing drywall. Make sure you provide adequate power and lighting circuits. Design based on ultimate uses. May need a sub panel.
Most of your heat loss is through the roof. Insulate there for the most bang for the buck.
Leave the existing drywall and insulation in place. Cover the drywall with OSB or other panels for protection from damage.

Bill
Designer and builder in Detroit

 

[e-tek]

I have a similar attached garage - in the Canadian climate. Although it would always be better to add width and insulation by making the walls 6" wide, I don't think you HAVE to. If you do, you'll only lose 2" on one side wall and one head wall - you wouldn't change the house wall. It's not much work either to sister some 2x2's onto the existing studs and re-insualte/VB.
If it where me, I'd leave the 2x4 walls as is. With new insulation and 6mil VB SEALED with acoustic sealer, you'll up your R value - and especially due to the wind! 26 years ago the insulation wasn't as good and the VB was likely thinner and not sealed.
The new garage door and window will also do wonders - so long as the door is tight to the seals on the outside.
What kind of heat in there? Electric baseboards or furnace ducted/shared from house?

 

[Porcupine]

Currently I have a small heater, only 1500 watts which is really not much at all. I thought about running a duct out to the garage when we get the furnace changed but that is forbidden due to the possibility of carbon monoxide leaking into the house. One reason for a change in electrical is to add the proper line to run a bigger heater, as well as to add a few extra plug ins and more ceiling lights (currently only one).

 

[creativecars]

What about something in the middle of the road, use 1X2’s to block out the wall on the house side, cover with VB, then fire rated sheetrock 5/8 and use Carlon B108R shallow electrical boxes for the additional outlets on that wall. You will get an increase in R value and fire rating, a place to run electrical, a new vapor barrier, and as I understand it, the air gap will help with r value and slow down sound transfer, all without disturbing old drywall or insulation. On the exterior wall an increase of R-value and vapor barrier would be even more beneficial. If your going to plumb for air, now would be a good time to do that too. Just my thoughts…