Friday, December 6, 2013

Mike Holmes: Choosing the Right Subfloor System

In Mike's last syndicated news article, he wrote about the pros and cons of hardwood versus engineered wood when it comes to flooring (see Hardwood: Real v. Engineered for more information). Regardless of the type of flooring you choose, be it hardwood, engineered wood, or even laminate, the subfloor you install it over is very important, especially if you're laying it over concrete. When laying wood over concrete it's important to remember several things. First, concrete is porous, and will wick up moisture. When wood meets moisture, rot and mold result, so it's important to protect your flooring -- and your health -- with the right products. Second, putting a plastic vapor barrier over concrete may not cut it. A 6mm plastic sheet can protect your flooring from moisture, but can trap in all that moisture between the plastic and the concrete, causing surface mold to grow. If you must install a floor over concrete, better products, such as Amdry Insulated Subfloors, are designed specifically for that purpose, allowing for better air circulation and insulation between the concrete and the flooring. "Anywhere the potential for moisture is high, you need the right subfloor system to protect your flooring." The Holmes Spot agrees!
From the Montreal Gazette:

Mike Holmes: Choose the right subfloor system

Protects your flooring from moisture and mould

After a decade, Mike Holmes still cares because he knows the work he, his crew and others do makes a real difference to the people they help.

Photograph by: Alex Schuldt/The Holmes Group, Postmedia News

Last week I talked about engineered hardwood floors, and one of the big benefits is that you can install them over concrete and below grade, like in a basement. That’s according to some flooring experts, but I think you need to be careful.
If I was going to do this I would add an extra layer of protection to make sure I have the right subfloor system to prevent mould and water damage.
Concrete is porous, and if we’re talking about the basement floor then eventually there’s going to be some moisture coming through the concrete slab.
So it’s important to make sure that: one, moisture doesn’t damage your flooring; two, moisture can dry out once it gets inside; and three, we prevent mould. To do that we have to incorporate the right products and materials.
Some flooring manufacturers might tell you that as long as you put down a six-millimetre plastic sheet barrier on the concrete floor, you can install any type of flooring on top — even real hardwood.
First, I don’t recommend real hardwood flooring in the basement. The risk of moisture or water damage is too high and hardwood costs too much. Even if you had the money to replace your flooring it’s a huge waste of materials and of a natural resource.
And the problem with putting a layer of plastic over concrete is that any moisture that penetrates through will be trapped underneath the plastic. It won’t be long before surface mould starts to grow. Your floors might be safe but your health might not, and any mould issue that isn’t fixed grows into a bigger problem — along with the health risks.
Now we have new products and materials made specifically for installing flooring over concrete and preventing mould, like Amdry Insulated Subfloors.
This product comes in panels — one side has foam insulation with raised drainage and air-circulation channels, and the other side has OSB sheathing. The foam also has a film that is moisture, mildew and mould resistant to protect the foam insulation and OSB from absorbing moisture.
When installing this product the side with the foam insulation faces down and goes against the concrete. The foam insulates and helps keep the floor warm by providing a continual thermal break across the entire floor surface, so it’s more energy efficient. It also prevents condensation because it keeps the temperature of the concrete floor from coming into contact with the temperature of the basement’s indoor air.
Before products like Amdry Insulated Subfloors were available, contractors needed to build proper basement subfloor systems themselves.
We’d start by putting down one-inch, rigid foam board and then 5/8-inch plywood or OSB screwed through the foam and into the concrete floor using Tapcon screws, which are designed for concrete. Then a low-expansion spray foam would be applied along the all exterior edges, and finally we’d seal all the joints with Tuck-Tape.
Think about how long that would take and how much it would cost the homeowner — not to mention that properly putting the whole system together takes the right skill and technique. But now with these new prefabricated panels, not only do we cut down on installation time but also on mistakes.
And it’s not just the subfloor systems in basements we have to think about. Kitchen and bathroom floors should also be watertight.
That’s why we install a waterproof membrane, like Schluter DITRA underlayment to prevent the tiles from shifting and grout from cracking, and to protect the subfloor from water damage. It can also be installed over the Amdry Insulated Subfloor system, so if you wanted to have tile in your basement there’s a safe way to do it.
Anywhere the potential for moisture is high, you need the right subfloor system to protect your flooring. Because when it comes to your home, it’s the stuff you don’t see that makes the difference between it lasting or not — and that includes what’s below your flooring.

Catch Mike Holmes on Holmes Makes It Right, Tuesdays at 9 p.m. on HGTV. For more information, visit For more information on home renovations, visit


  1. I just got my gravel floor basement done. (reno for a 1 bdr apt.) My contractor used a ply board with raised grey cells that went face down on the concrete. He said any moisture would dry out with this product. Mike, is this ok?

  2. I wish to place a home to be repaired , there is a 88year old woman in my area that need help with her home and her daughter who is handycaped that also needs help with her home also but I do not know if there is any way to get them the help they need.

  3. My dream kitchen has turned into a nightmare!!! I spent to much to have it redone.
    Cabinets was (refinished to dark). Ordered a stove sight unseen and it looks to industrial (stainless steel). The line are to strong for the look I wanted. Any advice.

  4. hi mike I live in a condo and I would like to replace my carpets with laminate flooring.
    Should I have to put a subfloor down first.

  5. I am planning to do my basement after many years delay, the original builder put insulation and wood at least three quarters of the way down each wall, instead of ripping out the whole thing and starting from scratch, I found a product Dri Core Smart wall that will easily or I was told its easy go over the original wall. The staff at Lowes recommended also a subfloor covering it rolls out in sheets and is blue I think it was called DMI(flat on top nodes on concrete to allow air/moisture flow) all I had to do was tape each section together...sounded easy...since I'm a novice...that last thing I built was a lopsided birdhouse...that even the birds wouldn't anything pre done and easy sounded good to me...the Lowes people also said I could lay my laminate floor that already has a foam backing right on top of the DMI...again sounds easy...but I'm unsure whether I have to put the subfloor in 1st...then the 2x2 on top...and attach it into the concrete floor...or does the subfloor butt up against the 2x2...question is what I am planning make any I have talked to reject the Dri Core Smart wall, as they prefer traditional walls, but I hate to rip out what was already done...and I don't see how to complete the traditional walls the rest of the way to the floor...just covering the whole thing makes more sense....I understand that this new product is just for the outside wall and all dividing walls will be traditional wood framing....does my plan make any sense...please advise

  6. We have had to gut everything in our farm house including the subflooring and now we are told that all we have to do is put down a roll of yellow floor vapor barrier. It is an old garage that was revamped into a house. We have no cement around the front of the house because everything was so rotted that the cement actually was no longer in place to hold anything. The carpenter didn't think we needed to redo the cement and that she is just putting a special vapor barrier underneath the new wood. I do not think it will last long sense the water can just come in at anytime because it has nothing to stop it. It was a double car garage so it has a slant from 5" to 3" (to the opening of the garage.)The out side is also cement and there are a lot of sinking areas that are right in front of the door.

  7. I had a engineered vinyl plank placed through out my house about 2 years ago on a cement slab, the floor is starting to shrink and curl, should the company and their contractors suggested placing down a moisture barrier before installing the floor?

  8. Hi Mike ,I am a big fan...I have a question...i bought a new house and they didn't cut control joints in the basement even though this builder usually is way past the 21 day curing... is it worth it to still do it or should I just leave it. There is a fairly big crack now but no lifting.The house is finished and I am afraid they will get dust through out the house. Are control joints necessary in a basement? I have heard people support both sides of the argument so I'm stumped...I trust your opinion

  9. Hello -

    I'm in the process of pulling carpet and abating some asbestos tile that's adhered to the (entire) lower level of a raised ranch. The lower level is below grade and the (original) tile is adhered directly to the cement slab. After the abatement of the tile and mastic, I would like to install the Amdry subfloor system.

    I have two questions:
    1. I know you use the quarter inch spacers with the Amdry system to allow for expansion and contraction; but it there any advantage of (also)using a low expansion foam around the perimeter (for extra protection)?

    2. I'm concerned that the height/thickness of the Amydry system will cause clearance issues with the baseboard heating system that's currently installed in the home. Any suggestions on how to best address? (the height of the Amydry plus the new wood floors will exceed the original tile adhered directly to the slab, need to lift the baseboard heating system? how?)

    Thanks in advance,

    PS - Hat tip to Mike and his team for the years of coaching they've provided. Very much appreciated.