Framing and insulating crawl space.


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Old 01-09-15, 09:29 AM
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Framing and insulating crawl space.

Im gonna be framing the crawl space its 59" high.

should i use metal or wood? if wood reg or blu wood?

roxul r22 or r24 or owens corning fiberglass?

do i need vapor barrier against concrete or just ontop of the batting after its installed...
 
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Old 01-09-15, 09:36 AM
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I'm not sold on blue wood yet, I'm still a PT on the concrete and white wood on top of that kind of guy. That said, I would glue foam on the walls, create an airspace of about an inch and then frame the walls inside of that and insulate those bays with Roxul.

No vapor barrier.
 
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Old 01-09-15, 09:52 AM
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Here's a link: BSI-009: New Light In Crawlspaces — Building Science Information

If the floor is dirt, then be sure to cover with a vapor barrier to block that moisture.

Bud
 
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Old 01-09-15, 10:09 AM
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its a crawl space thats 59" high its still part of the foundation as i have a multi level home. u guys have me mistaken i wanna frame the walls. They are cinderblock and the floor is concrete... also what is PT?

also how far should the framing be from the wall and what size wood?
 
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Old 01-09-15, 10:20 AM
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PT - pressure treated, needs to be used wherever lumber touches masonry. You'd need it on the bottom plate. It's best to erect a stud wall an inch or so away from the foundation wall and connect it at the top/bottom.
 
  #6  
Old 01-09-15, 11:46 AM
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All concrete or block walls below grade require moisture management. If there are any liquid water issues, they MUST be eliminated before the walls are finished. The other moisture issue is one most home owners are unaware of, moisture diffusing right through the walls. It can come from the soil directly through or wick up from the footings below and it can climb many feet, which it is doing right now. You don't see it because it is slow and it evaporates before it accumulates. But, mistakenly add a vapor barrier and that slo flow will raise the moisture level behind the VB to the same level that is deep in the soil.

Applying a layer of rigid foam insulation against the block wall acts as part of your insulation and as a break between the studs and the blocks. Adding another gap is not necessary and has the risk of allowing a flow of moisture vapor from below to rise up to where the blocks are much colder and result in condensation.

Having a concrete floor is good and essentially slows the moisture flow from below the slab. Ideally, it was installed with a good vapor barrier below it, but that is rarely the case. If the humidity in this space is more than desired, you would want a dehumidifier, or to circulate the conditioned house air into this now insulated space.

Before the new walls go up, be sure to air seal the rim cavities and the sill plate to foundation.

Bud
 
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Old 01-09-15, 11:58 AM
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Bud: Different than I thought - Am I reading correctly that you are saying to butt the studs up against the foam glued to the concrete walls? In other words, to eliminate the airspace I advised between the foam and the studs?
 
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Old 01-09-15, 12:22 PM
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Correct. The gap has been a traditional approach to keep the wood away from the wall and to provide a way to build a straight wall when there are variations. But somewhere in my archive of saved building science articles they caution that in the colder climates that moisture vapor will rise and condense and freeze on the upper cooler areas. Even when rigid insulation is placed against the blocks, it is always good to avoid a space where air can circulate. This link on a basement application using the same approach explains it better.
BSD-103: Understanding Basements — Building Science Information

Bud
 
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Old 01-09-15, 12:44 PM
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Works for me.

Thanks for the lesson
 
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Old 01-09-15, 01:42 PM
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So since I'm in a cold climate the foam barrier is pointless? If I do r20 or r22 rolux or fiber glass how far away should I frame from the foundation? Also are saying to seal the the bottom or top of the top plate or the frame I am putting up with spray foam?
 
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Old 01-09-15, 01:55 PM
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Nope, that's not what Bud said - go ahead and put the foam against the concrete and then build your stud walls (which you will insulate with Roxul) up against the foam.
 
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Old 01-09-15, 02:17 PM
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@wantboost "So since I'm in a cold climate the foam barrier is pointless?"
Quite the opposite, it is very important.

The air sealing I was mentioning is the perimeter of the house where it sits on the foundation. Once you built those walls you will have poor or no access to these areas so best to do it now.

Then, as Mitch just said.

Bud
 
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Old 01-09-15, 02:48 PM
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Does it matter if I use metal or wood studs?
The perimeter that I'm sealing is it at the top or bottom of the peice of wood?
If I mount the frame against the rigid foam won't the roxul be too deep and sticking out beyond the studs?
Also after roxul I should put a vapor barrier correct?

Also instead of framing walls could I use two layers of this foam? SilveRboard SB35S2000G 2-in x 4-ft x 8-ft Expanded Polystyrene Insulated Sheet | Lowe's Canada
 
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Old 01-09-15, 03:15 PM
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A quick look and that foam product seems to be a vapor barrier. We keep saying, no vapor barrier. If you have a water problem it needs to be solved before you build these walls. Then you use the pink or blue rigid insulation, 2" would be good, followed by the metal or wood studs directly against the rigid insulation.

As for sealing and insulating the rim joist, the best link I could find was a pdf, but I could not link to it, computer challenged. Search "BSC Information Sheet 408" and follow the building science link and it has some good illustrations.

Bud
 
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Old 01-09-15, 03:22 PM
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Here it is by itself:

No vapor barrier on below-ground walls.
 
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Old 01-09-15, 03:26 PM
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Wow no vb even on top of batting? My question is can I get away with just installing some type of foam. This site shows the r value of different foams. Which also has me confused cause the link shows higher r value than the description of products in big box stores. Insulating Your House | CMHC
 
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Old 01-09-15, 05:00 PM
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If I can find some rigid foam that's r20 or even 2 layers of foam can I use that alone as insulation and not have to frame? Possibly xps rigid foam?
 

Last edited by wantboost; 01-09-15 at 05:17 PM.
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Old 01-09-15, 06:49 PM
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Rigid foam needs to have an approved barrier covering it, typically drywall.

If you read through those links I provided they refer to the rigid foam board need some ability to pass moisture vapor, permeability. If you use too thick of a layer you will effectively have added a vapor barrier. 2" is about the max that will allow any drying to the inside. but in your climate it can't be much thinner, thus the combination of rigid foam board covered by a stud wall including cavity insulation and then covered with a layer of drywall.

Bud
 
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Old 01-09-15, 07:10 PM
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Wow. All that might add up to the same cost as doing spray foam instead
 
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Old 01-10-15, 05:01 AM
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The spray foam must still be covered with a fire rated barrier per your local code. Then, you have electrical that the stud framing provides space for.

I can't count the number of basements I've been in where they renovated them either before they new how or just ignored the moisture/mold concerns and I'm sure you have been in a few as well. They are easy to recognize, that musty basement smell and it is a sure sign they have mold growing somewhere. The bad news is that new home buyers AND insurance companies are catching on. People don't want to buy a moldy home and since Katrina, some insurance companies have excluded coverage for mold issues.

Yes, following the building science corp advice may cost more than expected, but it could be far less than doing it wrong. When I visit a home that has improved their basement the correct way, and there have been few, my nose has no idea I'm in a basement. I apologize if the advice I'm giving isn't what you wanted to hear, but the information in those links is the best I have found. I do wish you the best with your renovations and your DIY efforts.

Bud
 
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Old 01-10-15, 05:26 AM
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Good advice so far. Use Roxul R15 batts. They are made to fit 2x4 stud walls set at 16" oc. Don't compress any insulation. Roxul is fireproof, water proof and mold proof, and does not require the use of a vapor barrier, but do as suggested in the other posts.
 
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Old 01-10-15, 10:18 AM
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ok i have 2 options for rigid foam locally.
i believe u said to go with the 2"

Owens Corning FOAMULAR 150 2 in. x 4 ft. x 8 ft. R-10 Scored Squared Edge Insulation Sheathing-45W - The Home Depot

or

Owens Corning FOAMULAR 150 1 in. x 4 ft. x 8 ft. R-5 Tongue and Groove Insulation Sheathing-68WD - The Home Depot

also how do i seal perimeter plate with spray foam as u mentioned here a pic

 
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Old 01-10-15, 11:04 AM
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Figure 10 in this link from above shows two alternatives for detailing the rim cavity. Using spray foam is often not practical given the quantity and cost and it has to be covered as well. Cutting ans sealing a piece of rigid into each cavity and then adding fiberglass insulation or Roxul for extra r-value provides good insulation and access to the cavity if needed.

Canada has a variety of climates, but if you are in one of the colder areas, the 2" would be best.

Bud
http://www.buildingscience.com/docum...s/?full_view=1
 

Last edited by Bud9051; 01-10-15 at 11:05 AM. Reason: added link
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Old 01-10-15, 11:41 AM
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My climate here is the same as buffalo....
 
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Old 01-12-15, 11:46 PM
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I assume I'm using3" screws do they need to be a certain type? Also what should I use to secure bottom plate to concrete?
 
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Old 01-13-15, 02:36 AM
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I have frequently used Tapcons for concrete and with pressure treated lumber. You didn't say what the 3" screws will bu used for.

Bud
 
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Old 01-13-15, 09:56 AM
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What size tap cons to go Into concrete ? What. Kind of 3" screws for the framing?
Also should I paint cinder blocks with some sort of water proofing
 
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Old 01-13-15, 11:58 AM
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I try to use the shortest tapcon that will do the job as it's not always an easy task to drill the hole into the concrete and secure the screw. I rarely use screws on framing but a deck screw should work fine, drywall screws are too brittle to use.

Waterproofing is always best addressed on the exterior but it doesn't hurt to apply drylok to the interior side of the block for added insurance.
 
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Old 01-13-15, 12:31 PM
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3 3/4 tapcon? What do u use for framing nails?
One wall is already painted can I use drylok still?
 
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Old 01-13-15, 12:36 PM
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I would think a 3" tapcon would be long enough. 12 and 16 penny nails are most commonly used for framing [3"-3.5"]

Drylok is only effective when it's applied to bare masonry. It will have very little waterproofing effect when applied over paint.
 
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Old 01-13-15, 12:57 PM
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Regular drylok or extreme?
 
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Old 01-13-15, 01:34 PM
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I've never used the extreme version. The original drylok was oil base and had an extreme odor but really worked well BUT the latex version was so much nicer to apply when it came out that I think they quit making the oil base. I know I [and many others] quit buying the oil base in favor of the latex. Drylok works by penetrating the pores of the block and then expanding to give as water tight of a seal as possible. When it can't penetrate the masonry pores it's not as effective.
 
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Old 01-18-15, 09:59 AM
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how should i seal/insulate this side that has the joist against the wall...

 
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Old 01-18-15, 10:53 AM
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Is there siding on the other side of that joist or is there a gap and then a rim joist on the outside?

If that is the outside joist (we call it the rim joist, then some fiber insulation right over those wires should be fine.

Bud
 
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Old 01-18-15, 11:44 AM
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It's right against the concrete. The outside is brick. Against the concrete I will be putting rigid foam first...... should I seal the bottom with spray foam?
 
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Old 01-18-15, 12:51 PM
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Seal with the foam and then cover that joist however you wish. With wiring already there i would just push some fiber insulation up there as best possible.

Bud
 
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Old 03-17-15, 08:59 AM
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hey guys i had my energy audit today as we get so rebates in my area.

1: so to confirm if is use the 2" owens corning which is r10 plus roxul r14 is adequate for the the crawlspace (which in my case is a shallow basement only 59" high)
i'll be using this Owens Corning FOAMULAR 150 2 in. x 4 ft. x 8 ft. R-10 Scored Squared Edge Insulation Sheathing-45W - The Home Depot

2: is r24 enough for the headers correct? and when i put rigid into header i can seal edges with spray foam for extra draft control or not necessary?


3: Instead of framing can i use double sided tape on the batts and put them against the rigid foam?

4: also home inspector i guess is still going by old ways he said put r24 and then a vapour barrier
 
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Old 03-17-15, 03:21 PM
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What glue to attach rigid foam to block wall?

I'm gluing against interior cinder block what glue is ok to use??
 
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Old 03-17-15, 03:24 PM
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can I glue roxul to owens corning rigid foam??

Instead of framing my shallow basement can I just glue the roxul to the rigid foam?? If so what glue is safe??
 
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Old 03-17-15, 03:30 PM
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vapour barrier or no vapour barrier??? (in NORTH EAST cold climate)

I'm in toronto Canada I guess our weather is like buffalo....I'm seeing so much conflicting information. Building science seems for more humid and warm climate based.
I'm insulating a shallow basement that is only 59" high. With 2" owens corning rigid foam and then r14 roxul.
Do I need a vapor barrier or not?? The space is not liveable I WON'T be dry walling. But my concern is about moisture
 
 

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