Basement Framing and waterproofing

Question Icon
Posted by: from Toronto
1/19/2013 at 10:37:56 AM

We are finishing our basement after a flood. Originally planned to just reinstall panelling...however, have switched gears and are going to do drywall. We have already painted exterior walls with waterproof paint...filled cracks in cinder block foundation. The framing is done with normal 2x4's.

Are we suppose to have a gap between the concrete and the wood frame? I read 1" in another forum.

Also, we are using Roxul(R14) insulation...I believe it is comfort batt for exterior walls. Basically the frame is up and insulation in, directly against the concrete. We can modify if needed. Or can we just add vapour barrier and drywall?

Also, should there be a gap frame the frame to the concrete floor? We were planning on something like an allure flooring with rubber back.

Any advice is greatly appreciated?

User Icon
Date/Time1/19/2013 at 11:27:00 AM

Hi Melissa,

Leaving on 1" space between your studs and wall is good to allow for air to circulate however is not a requirement. One should never place their bottom plate directly on the concrete floor as a sil gasket is highly recommended for such an application. You can pick up a roll fairly inexpensively at any of the large big box stores.

Hope this helps.



Toronto Custom Concepts Inc.

User Icon
Date/Time1/19/2013 at 12:27:06 PM


Dave is correct. The space isn't necessary but isn't a bad idea as it allows some air flow. In many areas, (not sure if this is a national code) there must be a barrier between the concrete and the bottom plate (the wood that runs horrizontally along the floor). Or you can use pressurew treated wood. The main reason is that moisture can cause rot in the "natural" wood and produce mould and/or weaken the structure.

It sounds as though you are doing it correctly. Read the instruction on the Roxul because you dont want to over pack or squeeze the product, it must be relatively loose to do the job. Use a 6 ml. plastic vapour barrier ... not a light weight item. Tape all the seams with Tuck tape to make it as air tight as possible.Then the drywall.

Have fun with it. I'm sure you'll do a good job.

Regards from the west.

User Icon
John from JALS Corporation in Welland
Date/Time1/19/2013 at 12:53:36 PM


Sounds like you have every thing under control. Just make sure that any sill plate that touch the concrete floor have a sill gasket and are dry after the flood.

User Icon
Date/Time1/19/2013 at 12:58:23 PM

Hi There,

The should be building paper between concrete and wood according to code. It prevents future moisture. Then insulation vapor barrier and drywall. There does not have to be a gap between the bottom plate and floor. Usually building paper or pressure treated wood as bottom plate of wall.

Degruter Home Improvements.


User Icon
Date/Time1/19/2013 at 1:21:55 PM

You should have a gap of approx 1" between the back of the framed wall and foundation as well as a layer of tar paper on the back side of that same framed wall between the wall and foundation.

You should put a vapour barrier on the outside of the wall before you install your drywall.

As long as you install a poly wrap under the bottom plate you will be up to code. You need the seperation between wood and concrete.

I have never been a very strong proponent for rubber back carpet on basement floor only because of the dampness that is in concrete.

I would put down a delta floor type substrate, this serves a couple of purposes. First, it will increase the temperature of the inside of the room by having that seperation from the concrete and secondly if there is ever an issue with water the delta floor will act as a waterproof membrane and allow water to drain to your floor drain without damaging your floor material.

Hope this helps out.

User Icon
Randy from RJ Interiors in Orillia
Date/Time1/19/2013 at 5:27:00 PM

I like a air space between insulation and concrete wall.

Also super six vapor barrier is required on warm side of wall (on top of framing and insulation on inside of framed wall).

Also a vapor barrier is good on floor underneath wood framed wall, (between wood and basement floor).

User Icon
Date/Time1/19/2013 at 8:47:23 PM

Wood should never touch cement as wood will take the moisture from the cement. You should have a pink plastic barrier between the wood and the cement floor.

You have to have your vapour barrier on the warm side of the insulation then top with your drywall.

User Icon
Date/Time1/20/2013 at 12:13:57 AM

Hello Melissa,

Another possible solution for areas of your floor prone to some penetration wouid be PVC 2x4s that we mfg. For one basement . The owner was exctatic with the resuly. No more rotting wood. He jus vaccums up spills and no longer worries.

Good luck


User Icon
Date/Time1/20/2013 at 8:20:08 AM

Sounds like you guys have it all right, except the bottom studs (sill plate) should be pressure treated.

You can buy a foam type material that is made to sit in this area called a sill gasket. Just staple it to the bottom pressure treated board, and when building the wall make sure the sill gasket faces the concrete floor.

Also, ny protition walls should be built with a floating sill plate, so any shifting won't put pressure on the existing floors on the house.

User Icon
Dolphin Construction Co. in Ottawa
Date/Time1/20/2013 at 10:46:31 AM

Good tips, all of them.

I would go with CC Spray foam insulation instead.

User Icon
Keefer from Sunvalley Homes in Edmonton
Date/Time1/20/2013 at 3:09:23 PM

Water prof paint with not be enough for a cider block foundation. I would recommend putting a thin coat of morter on the entire wall.

For the frost wall framing 1 in gap b'te went the foundation wall and framing is recommend but not required. The air space will allow moisture to dry quicker.

Ensure u have wrapped the bottem plate with ploy between the slab and framing. To ensure air is sealed and plate is portected.

The insulation I would recommend due to your moisture problem should be a r20 stryo span.

User Icon
Melissa in Toronto
Date/Time1/21/2013 at 12:03:12 PM

Thanks everyone for your advice. We went with the sil gasket between the wood and the concrete seeing as the frame was already built. We still have to finish framing the windows and then do the vapour barrier. Then dry wall!

User Icon
Date/Time1/21/2013 at 2:41:06 PM

Hi Maria,

Yes you should have a 1" air gap between the back of the 2x4 and the concrete so the air can move behind the insulation.

If you just poly and drywall, you will most likely have a mould problem. If you donnot want to correct the framing issue, then your other option would be to have a spray foam contractor spray all the exterior walls with foam insulation. This is the premium installtion!

As for the 2x4 bottom plate touching the concrete, you should have a foam sill gasket seperating direct contact with the concrete floor.


User Icon
Dave from 360renos in Navan
Date/Time1/22/2013 at 6:56:04 AM

Morning Melissa

Unfortunately there is a lot of misinformation being posted about how to finish your basement

Yes, you want your framed wall off the concrete foundation by an inch so that you reduce and remove thermal bridging.

You DO NOT want air circulating behind the wall. You do not want warm air reaching your cold foundation walls

Ontario building Code now requires R20 insulation in basement walls.

Do the correct steps in the right order and you will have a successful project.

Some info with the links below that will help you understand best practices to insulating your basement. I give copies of portions of the this to help home owners understand all the steps when we are offering quotes to home owners.

Click on Basement Insulation Systems tab

Have a great day


Search the TrustedPros directory and discover the best contractors in your area.

Find your home service pro
Great renovations start with a great contractor.

Since 2004, TrustedPros has been helping homeowners find the right contractor for their home improvements and repairs.

Post Your Project

Within hours you'll be comparing offers from top-rated professionals. It's free to post and you're under no obligation to hire.

Trustedpros Inc. does not warrant the accuracy, completeness, safety, legality or usefulness of any Content, or Whether Content is Current and up-to-date, and TrustedPros Inc. Shall have no liability whatsoever with respect to your use or reliance upon any content or for content being removed or otherwise ceasing to be available. Please refer to the terms and conditions of use of this websites for more details.

Get Free Estimates

Post your project and compare offers from top-rated pros.