subfloor on slab on grade

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Posted by: from Halifax
2/17/2011 at 8:26:25 AM

I am looking to add a subfloor to a slab on grade constructed home. Has to be to code. Could you provide step by step instruction, or guide me to a site where I could get the information I need?


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Rod. from Artall R.M. in Toronto
Date/Time2/17/2011 at 1:43:41 PM

Hello Gary,

You should start from this web site:

Depending on floor finish you plan to use, on top of concrete there should be vapour barrier, wood sleepers, plywood, and felt w/plastic or foam sheeting. This in case you would have laminate or hardwood flooring.

Vapor barrier has to be used always, even in case of ceramic tiles as finish.

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Rod. from Artall R.M. in Toronto
Date/Time2/17/2011 at 1:48:50 PM


THIS IS THE CORRECT link to follow.

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Date/Time2/17/2011 at 6:33:30 PM

I am not a big fan of laying a 6 mill vapour barrier and wood sleepers as a sub floor over concrete. The plastic vapour barrier can cause a build up of moisture and promote mould growth. In addition, the tapcons used to secure the wood sleepers penetrate the plastic anyways. There are other solutions available that you may wish to consider. If height is not an issue and you are concerned about existing water issues, there is a product called Dricore that is effective. My favourite system is to use Dow's XPS insultion as a thermobreak and vapour barrier and then applying plywood over top.

Hope this helps.

kingsway Construction Inc.

Glenn Rosborough

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Date/Time2/18/2011 at 10:37:00 PM

The dricore system avaikable at home depot is my choice for concrete,

They will give you a free dvd for installing.

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David in Toronto
Date/Time4/5/2011 at 9:58:10 AM

In place of a subfloor, try Sika MB Primer, and a full spread adhesvie from Sika, or Sika Accoubond. This is how it is down on slab on grade in the commercial market, and in that environment there are warranties to be sensitive to.

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