# Garage Conversion w/raised floor



## cjh234 (Jul 28, 2016)

Hello,

I am planning a reno of my small one car garage (about 235 sq ft), enclosing the door and raising the floor level with the rest of home which is about a 14" difference. It will be half laundry room/1/2 bath and 1/2 a large bonus room of sorts. My question lies on how best to insulate and avoid moisture under the newly created crawl space. 

My plan is:
1. 6 mil poly over the existing slab running 6" up the walls and all taped together
2. Rockwool R-23 between the floor joists
3. sub floor on top
4. vinyl flooring on top of subfloor

Is this the best option in my situation? I am afraid to do it wrong and experience mold or other issues later. Located in Nashville, TN

Side note, there is an air vent coming through on the side of the garage connected to the home which goes in to the crawl space under the home. This is where I plan to run plumbing through and thinking maybe I should enclose it with a foam board from the home's crawl space side to prevent air entry and keep out pests. Thank you.


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## chandler48 (Jun 5, 2017)

You skipped one step. Building the floor joist system. Have you a plan for that? You don't want to lay any wood flat and attach it to the concrete. You'll be putting a kazillion holes in your barrier. Build your joist system free standing. You may only be able to achieve 12 1/4" of the 14 you desire, using 2x12 lumber and subfloor of 3/4" Advantech.


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## Nealtw (Jun 22, 2017)

Do you have a problem with moisture in the crawlspace now?
Length and width inside garage now?


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## cjh234 (Jul 28, 2016)

Nealtw said:


> Do you have a problem with moisture in the crawlspace now?
> Length and width inside garage now?


Thank you both for the replies. No moisture that I have noticed. Going to do the plastic taped to the concrete test tonight to see. The garage measure about 21.5' x 11'. The plan was to have it with a free standing joist system.


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## Nealtw (Jun 22, 2017)

cjh234 said:


> Thank you both for the replies. No moisture that I have noticed. Going to do the plastic taped to the concrete test tonight to see. The garage measure about 21.5' x 11'. The plan was to have it with a free standing joist system.


Does the foundation curb come above the floor on the far side? 
If you have no problem with moisture now, don't change it, don't break it.


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## cjh234 (Jul 28, 2016)

Nealtw said:


> Does the foundation curb come above the floor on the far side?
> If you have no problem with moisture now, don't change it, don't break it.


attaching a photo of the height and curb on the side closest to house and one of how the other two walls look.


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## Nealtw (Jun 22, 2017)

cjh234 said:


> View attachment 645970
> 
> 
> attaching a photo of the height and curb on the side closest to house and one of how the other two walls look.


How high is the top of the rim joist above the concrete and how thick is the subfloor?


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## cjh234 (Jul 28, 2016)

Nealtw said:


> How high is the top of the rim joist above the concrete and how thick is the subfloor?


top of the rim joist is about 18” off the concrete pad and subfloor is 3/4”.


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## Nealtw (Jun 22, 2017)

cjh234 said:


> top of the rim joist is about 18” off the concrete pad and subfloor is 3/4”.


Off the curb concrete?


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## cjh234 (Jul 28, 2016)

Nealtw said:


> Off the curb concrete?


Off the concrete slab


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## Nealtw (Jun 22, 2017)

cjh234 said:


> Off the concrete slab


How high is it off the curb?


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## cjh234 (Jul 28, 2016)

Nealtw said:


> How high is it off the curb?


It is 10” off the curb.


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## Nealtw (Jun 22, 2017)

cjh234 said:


> It is 10” off the curb.


One the house side just lag bolt a ledger to the house and use hangers for 2x10 joist.
If you are adding windows I would do that first.
On the outer I would I would put 2x12 blocks between the studs, add a ledger and hangers.


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## cjh234 (Jul 28, 2016)

Nealtw said:


> One the house side just lag bolt a ledger to the house and use hangers for 2x10 joist.
> If you are adding windows I would do that first.
> On the outer I would I would put 2x12 blocks between the studs, add a ledger and hangers.
> View attachment 645986


This is great. Thank you. As far as underneath, if I’m not seeing an moisture I should skip the vapor barrier? Wondering about the best insulation options for the space as well, any thoughts there?


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## Nealtw (Jun 22, 2017)

cjh234 said:


> This is great. Thank you. As far as underneath, if I’m not seeing an moisture I should skip the vapor barrier? Wondering about the best insulation options for the space as well, any thoughts there?


Rock wool batts between the joists and vent below. What is the plan for the big door and what siding does the garage have?


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## cjh234 (Jul 28, 2016)

Nealtw said:


> Rock wool batts between the joists and vent below. What is the plan for the big door and what siding does the garage have?


When you say vent below, you mean keep the existing vent open between the two crawl spaces? Or install a new vent? Adding a photo









Will be removing the garage door and framing in with a window in the center. It’s a brick exterior and we will have a mason come brick in the outer wall. We’ve been advised to spray spider insulation in to the exterior wall cavities.


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## Nealtw (Jun 22, 2017)

Before you go with brick, drill 6" deep hole thru the slab there and confirm there is a foundation of the slab is thick enough for the brick layer.








What is the correct way to support a veneer brick front...


Currently getting estimates to repair my veneer brick front home, and contractors are telling me two different things. Basically, the veneer brick front sat on a floating driveway slab without proper footers. This causes movement. Several contractors have told me the concrete needs cut...




www.diychatroom.com


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## cjh234 (Jul 28, 2016)

Nealtw said:


> Before you go with brick, drill 6" deep hole thru the slab there and confirm there is a foundation of the slab is thick enough for the brick layer.
> 
> 
> 
> ...


Had not thought about that. Thank you for mentioning that. What should I be looking for with the hole? If it is 6" of concrete it's all good?


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## carpdad (Oct 11, 2010)

Spray foam probably will cost you more in the contractor's preparation than the actual insulation value you get out of it. If mine, absolutely no spray foam for that amount of insulation you're going to do. Rockwool, example, give you bit more than fiberglass but denser rockwool may be more sound dampening (though a window defeats it) and more water resistant. Also option is filling in with 2x6 there for more r value and cost effective material.
Bricking, make sure you see the bricks themselves and approve the match. Nothing worse looking if not matched. Existing edge cut bricks should be removed so they are weaved in with full bricks. It will cost more. If painted bricks, moot. At least remove the trim or channels around the current opening. Brick on brick. In nj and there are many of them and it is outstanding eyesore.


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## cjh234 (Jul 28, 2016)

carpdad said:


> Spray foam probably will cost you more in the contractor's preparation than the actual insulation value you get out of it. If mine, absolutely no spray foam for that amount of insulation you're going to do. Rockwool, example, give you bit more than fiberglass but denser rockwool may be more sound dampening (though a window defeats it) and more water resistant. Also option is filling in with 2x6 there for more r value and cost effective material.
> Bricking, make sure you see the bricks themselves and approve the match. Nothing worse looking if not matched. Existing edge cut bricks should be removed so they are weaved in with full bricks. It will cost more. If painted bricks, moot. At least remove the trim or channels around the current opening. Brick on brick. In nj and there are many of them and it is outstanding eyesore.


Definitely want to avoid spray foam. Will stick to the rockwool between joists and doing the spider insulation blown in behind the existing walls. I just only have the one existing vent going in to the home crawl space, is that sufficient enough to consider the new crawl space under the raised floor "vented" or is is better to seal it off and treat the space as enclosed? 

Appreciate the thought on the brick, trying to make it look as natural as possible, but not against painting the brick down the road.


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## Nealtw (Jun 22, 2017)

cjh234 said:


> Had not thought about that. Thank you for mentioning that. What should I be looking for with the hole? If it is 6" of concrete it's all good?


Drilling the hole hole will only answer one question, or I guess with a longer drill you coulld look for a brick ledge. I guess some where else you could find at what level the brick ledge is. I was thinking you could put some kind of vent out the front.


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## cjh234 (Jul 28, 2016)

Nealtw said:


> Drilling the hole hole will only answer one question, or I guess with a longer drill you coulld look for a brick ledge. I guess some where else you could find at what level the brick ledge is. I was thinking you could put some kind of vent out the front.


Wasn't planning on adding any additional vent, so perhaps sealing the other one off makes sense to create a sealed crawlspace area. I pulled up the trash bag and tape today and saw no moisture underneath. I had an insulation guy out today and he mentioned still using a vapor barrier, adding a layer of foam board on top of the plastic and up the side wall 6" to prevent moisture and insulate...thus removing the need for rockwool between the floor joists. Does this make sense?


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## Nealtw (Jun 22, 2017)

cjh234 said:


> Wasn't planning on adding any additional vent, so perhaps sealing the other one off makes sense to create a sealed crawlspace area. I pulled up the trash bag and tape today and saw no moisture underneath. I had an insulation guy out today and he mentioned still using a vapor barrier, adding a layer of foam board on top of the plastic and up the side wall 6" to prevent moisture and insulate...thus removing the need for rockwool between the floor joists. Does this make sense?


Neither will give you a warm floor, mostly you are after keeping pipes from freezing.


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## cjh234 (Jul 28, 2016)

Nealtw said:


> Neither will give you a warm floor, mostly you are after keeping pipes from freezing.


Got it. Hoping it will help a bit to keep things warm in the rooms above. That's the main goal, but I was a bit more concerned with creating moisture induced mold growth underneath the crawl space.


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## Nealtw (Jun 22, 2017)

cjh234 said:


> Got it. Hoping it will help a bit to keep things warm in the rooms above. That's the main goal, but I was a bit more concerned with creating moisture induced mold growth underneath the crawl space.


The biggest problem after water leaking in is warm, moist, dirty air going down from the house and finding cold where it will condense. Venting helps with that or with sealed areas they often put in a dehumidifier.


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