Frame overtop of rolled batt insulation?

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Posted by: from Burlington
11/13/2012 at 9:03:35 PM

My unfinished basement insulation is the rolled batt style that only extends about halfway down the walls secured with vapor barrier plastic (typical basic builder style).

Temperature and moisture has never been an issue - I live in Burlington Ontario.

Can I frame right overtop of this insulation or does it need to be removed?

Thanks for the advice.

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Josh from Honest Painting in Hamilton
Date/Time11/13/2012 at 10:19:45 PM

Hi, because of the temperature difference between the two I wouldn't recommend it at all, it provides a gap for moisture to create mold. The rolled insulation that is on there, is also r-7 which is of no use to provide your basement with warmth. Replace the batt completely with a minimum value of r-20, I would recommend spray foam.

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Bourdeau Renos in Ottawa
Date/Time11/13/2012 at 10:21:51 PM

You can frame over it, the blanket insulation has a vapour barrier on both sides so there is no risk of moisture. That insulation is only an r12 blanket. When you're done your framing, if you're turning it into a liveable space, you would have to bring the insulation up to r22. Your best bet is to vapor barrier from the blanket to about 8 inches from the ground. Fill it with r22 batt insulation, vapor barrier it again and then you can put drywall up. The 8 inches will allow for if there's a flood in the basement, you have that 8 inches before the water wouldtouch the insulation(leading to mold).

I hope this was helpful.

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Date/Time11/13/2012 at 10:43:56 PM

You can but I would never do it or recomend it. That stuff is just crap for a multitude of reasons. You can spray foam the walls but it is not cheap.

A more cost effective solution is 1 1/2 or 2" ridgid insulation (not the white stuff) glued to the wall (you don't need a lot of glue it is just there untill you frame the walls). That gives you a continuous thermal break just like the spray foam. Then a 2x4 wall with Roxul insulation and then your vapour barrier.

If you want a warm basement, think about adding 1 - 1 1/2" ridgid insulation under your sub floor. It adds to the costs, but is well worth it to be comfortable and actually use your basement.

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Bourdeau Renos in Ottawa
Date/Time11/13/2012 at 11:40:06 PM

The problem with rigid insulation is that it's only r7(with the 2" foam board).

I've worked with city housing on insulating basements with the r12 blanket and have had tenants build over it to complete a basement. I was also responsible for tearing down finished basements to return it to it original state. if the basement is properly sealed, you should have no worries about building over the blanket insulation. In my previous post gave you a brief description of what you can do. Here are step by step instructions on what you can do.

Install the vapor barrier about 3 inches up the blanket insulation(you can secure it with tuck tape), make sure to leave about 6 inches of vapor barrier on the floor to provide a barrier for the framing.(In my previous post it says to leave room at the bottom for moisture. That's only if you're going to install another blanket instead of batt insulation)

Frame up your basement(anywhere the wood is on the concrete, have vapor barrier under it).

Install r22 batt insulation in the cavity from top to bottom. Cover with vapor barrier from top to bottom and staple in place.

You'll save about $400 doing it this way compared to spray foam kits.

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Date/Time11/14/2012 at 1:14:17 AM


Yes you can frame overtop of this insulation but please make sure that you do not have a double vapour barrier.

You will need to remove portions of the vapour barrier prior to or after installing your framing studs on the exterior basement walls. It can be done by providing slits with a razor knife in the existing builder style of vapour barrier. If there is any concerns with providing enough cuts or slits in the vapour barrier then it is wise to remove all of it or as much of the vapour barrier as possible. If there is any doubts or concerns then I would suggest to remove it completely.

If it is done properly then it is added insulation and saves on labour and, of course, the cost of the removal and disposal of the existing combination insulation and vapour barrier as it will save on the dumping of the material in the land fill or where ever the disposal or construction company disposes of the waste material. Also remember to install insulation in the joist spaces on the exterior walls where accessable and extend the vapour barrier to the underside of the main level sub-floor where accessible.

Wood framing members must not be in direct contact with concrete floors or poured concrete foundation walls or concrete block foundation walls. Black tar paper, tyvek or other acceptable OBC approved material should be used as a contact separation.

Hope that my reply has been helpful.

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Date/Time11/14/2012 at 2:26:29 AM

Hi Scott,

I agree with Lou and strongly suggest you do not put multiple layers of vapour barrier in the walls. This can actually trap any moisture within the walls and lead to mold problems.

You can certainly leave the existing insulation there, and fill your wall cavities with insulation after you are finished framing.

What I like to do in basements is put down a subfloor and build the walls on top of that, therefore seperating your floor and your walls from any moisture that may get in to the basement. It costs a bit more but the extra costs would seem small if there was ever water in the basement.

Hope this helps,

Bill Clawsie

Clawsie Contracting

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Date/Time11/14/2012 at 7:28:55 AM


If you do not want to change the application to another form of insulation (batt, spray foam, rigid, etc.). The insulation blanket is sufficient but I would add a secondary blanket underneath so no you will have insulation from floor to ceilng. The cost is minimal.

Thank you

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Date/Time11/14/2012 at 7:30:14 AM

Yes wall can be installed up against, keep in mind that you do loose that amount of space on the perimeter this is agood time of year too check temperatures floors walls. Concrete floor is usually 50 degrees and should be insulated as well or sub floor.

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Date/Time11/14/2012 at 5:21:38 PM

I would remove it. Save the insulation as you can use it. Install tar paper on all outside walls that are concrete. Frame your walls with green board against the concrete floor. And if not using green board for your studs, pick up a gallon on end sealer and do the bottoms of each. Run any electrical or venting etc.

Then insulate the walls. If you are using the builders R-12 you will have to cut it to fit your 16" on center studs but that no big deal. The bottom foot or so of insulation, I suggest using a water and mold resistant insulation. Now vapour barrier all the outside walls. Tape all loose ends of the plastic. You are now ready for drywall. Remember to apply the drywall to the cieling first, as the drywall on the walls adds strength to your cieling sheets when applied against it.

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Date/Time11/14/2012 at 11:36:45 PM

Hi Scott

I would remove it and damp proof your basement walls. Then wrap the bottom of your walls so the bottom and both sides are covered or build on top of your subfloor which I would recomend planton and T&G osb.

Also I would suggest running your heat ducts down the walls and open them so some heat and air flow go under the floor. This will help warm your floors and help dry any moisture if any now or in the future.

Hope this helps in your basement project.

Scott Wilson

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Date/Time11/15/2012 at 7:25:24 AM

If you are having no issues with the existing insulation and vapor barrier then build away. Upgrade if you want, but if you find it warm enough down there and you are having no issues with moisture, then your r12 is fine.

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Scott in Burlington
Date/Time11/15/2012 at 7:35:14 PM

Wow - thanks so much for the replies! This was my first post on this forum and it was a wealth of information.

Sounds like it is ok (but not necessarily ideal) to frame over this type of insulation as long as I heed the advice regarding moisture mitigation.


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Date/Time11/16/2012 at 8:05:30 PM

Hi Scott,

You can certainly frame over the rolled batt insulation if you wish. Typically it is an R12 value. If you wish to increase to a greater R value, there are many other options and applications that you could use. Hope this helps.

Thank you


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