DIY How to Install a Basement Subfloor

Follow my simple process for a warm dry basement.
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Tools We Used:
dewalt laser level
dewalt drill set
my favorite olfa knife
dewalt circular saw
milwaukee tape measure
dewalt mitre saw
tile cutter
laminate cutter
dewalt reciprocator saw
makita jigsaw
dewalt mixer
angle grinder
grinder wheel for tile
drywall trowel

Video Editing Services by:
Moskal Multimedia

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Terri Light says:

I have been trying to puzzle out refitting our garage into an art studio. It is at level and contains electrical but no plumbing. Would this be a suitable choice? And , fyi, it is currently workshop storage, no car parking for 30 years.

Dan Hirsch says:

How would you transition from this subfloor system to an existing sliding door in the case of a walkout type basement?

Khalil Al Khayr says:

I wish I could do that

Microtic says:

I plan to put down a Schluter Kerdi-Shower system. Is there any issue with putting this on top of the OSB / DMX AG? Thanks!!

Jason Parrott says:

I have an old home, with rock basement walls. Do you have a video for insulation of this type of wall?

Aquil Jannah says:

how did you ensure waterproofing before building?

Pample Moose says:

Someone suggested placing a landscape fabric onto the floor before you place the dimpled black roll material down. They claim it eliminates a potential squeaking floor when you walk on it. Isn’t landscape material made from organic material? If so, it should never be used in direct contact with the concrete floor. Your opinion? Thanks!

Paul Brown says:

You mentioned Tapcons stripping out. Pull the screw back out and add one or two pieces of rebar tie wire then put the screw back in.

Mark Hatfield says:

Jeff – poured through the comments, I apologize if you’ve answered, but what size tapcons are you using? (assuming 5/8″ OSB with the DMX)

John Lennon says:

Fantastic video! Just trying to have it all sink in…thank you and keep ’em coming.

Oliver Clothesoff says:

It would have been great to see how you worked the door transition and installed some walls. Keep up the great work!

Jordan Terrier says:

We have an addition with garage underneath, the floor is brick. we turned it into a four season room but the floor is so cold (New England) What’s the best way to insulate the flooring cost effective?

danny302 says:

Seriously leaning towards this system for my basement…  Would it be a good idea to attach rigid foam to the walls then use this system on the floor and then build your walls on top of this floor subsystem?  That would keep room fully encapsulated from the concrete, wouldn’t it?

Alin Jian says:

Great videos. Very informative. Is there a video that shows how to fix large irregular subfloor holes. Eg maybe a chimney or laundry chute used to be there and was removed so now subfloor needs to be “patched”.

David_Stacey Kromm says:

Hey quick question hopefully you can help me with. Going to start installing my sub floor shortly using this method but not sure what to do with my exterior walls which are already framed, insulated and got poly on them. The poly comes down to the floor and has a little flap like maybe 1-2″ in spots. The joint at the floor is sealed with acoustical sealant (Black tar). I have seen videos for like the Delta FL that says you just over lap the poly with the Delta and seal it but I don’t have nearly enough to do that, and it would trap moisture under my floor. If I leave a gap at the edge wouldn’t that also be bad as it would allow moisture to escape up the front of the drywall?

Striker Thunderlick says:

“A few holes” lol… And the tapcon just sinks with ease…….. LOL!

Fayaz Rahman says:


Where do you purchase the DMX from?

wind river says:

Hello Jeff. This is great! I went out and purchased the DMX Ag and OSB after watching your video. I am in the Toronto area. My plan is to glue 2 inch thick EPS rigid foam to the exterior cement basement walls and then frame with 2×4’s and batt insulation. If the subfloor goes in first do I install the EPS foam boards down to the cement floor or just to the OSB? Not sure if the subfloor would be sealed or left open for air flow where the EPS and subfloor meet. I would think that air flow from the subfloor into the batts(that would be behind a poly vapour barrier) would not be a good thing. Thanks,

JPI Concepts says:

Do I need to put a subfloor on cement in bathroom? Or can I put tiles right in my concrete.

Love Life says:

Hi, in an apartment, would laying an under chip board underlay help with noise also? As well as an overlay.

Ian Couper says:

I did this over a concrete floor at the cottage. It was recommended by several people to use landscape cloth under the Delta Fl to avoid a clicking noise when people walk on it. Worked well. Any thoughts if its a little overkill?

Brian Boyce says:

Hey Jeff – awesome videos I’ve spent hours watching them. They’re exactly what I need, thank you! I’m just south of you (in Belleville) and I’ve got a new build with an unfinished basement. Still in the planning process but looking to start working soon.

Seems like you suggest subfloor first and then interior framing? I gather that means no need for pressure treated on the base plate? Is it possible to use a Ramset through the subfloor into the concrete or is drilling/screwing my only option?

I’ve read a few rather opinionated comments regarding the OSB, and I know this is your system that has worked for you, but have you ever laid laminate directly on top of the barrier? I’m looking at using the grey Delta-FL from Lowes but I’ve got about 1000 sq.ft to finish. I’m all for over-building and doing it right but if it really is overkill and I’d be fine right overtop of the Delta-FL (with an underlayment?) then it would definitely be a big cost saver.

Thanks again for the advise, love the channel! – Brian

Jon G says:

Is the OSB acceptable for stick-on carpet tiles? Or should I go with plywood? It’s a pretty big cost difference and I’m seeing conflicting advice elsewhere.

JH says:

Can I install these product over my uneven basement floor?

fastdr88 says:

I just bought a house and I’m redoing the basement. I love your videos I’m learning a lot. In the basment in my new house already has walls up so then I should use the blue product under my flooring?

CompCrasher86 says:

Hi Jeff this really seems like the Cadillac of subfloors for the basement. I just measured and I have 76” from the slab to the bottom edge of my I-beam (low bulkhead point in the basement). The bulkhead is just after the bottom of the stairs so you won’t run into it coming off the stairs but it’s going to be there every time you enter the room. Think I’ll have enough head clearance for this system?

LetOffSomeSteamBennett says:

Hi Jeff, I’ve learned alot from your videos. I have a mudroom off of the garage that I need to renovate. The room itself is on a concrete slab with copper lines running through it for the washer/dryer. The rest of the house has a basement beneath it. With that scenario, should I still use your method of the DMX + OSB on top of the concrete? That room gets pretty cold as well so insulating it is another factor, especially with the concern that there are water lines in the concrete I’d rather not see burst in the winter. The wife wants a checkerboard style vinyl tiles in there. I’m trying to come up with a plan for that area where it’ll be mold/mildew resistant, warm, and safe. Any tips would be appreciated. Keep up the good work.

Philip B says:

I’ve used this product before.. it’s pretty good ( the Delta FL) I used Delta MS since it comes out a little cheaper /sq ft.
One thing I would recommend is to put landscaping fabric BEFORE putting down the plastic underlay to eliminate the clickety-clack noise if some floors are a little uneven. (Recommended by the manuf.)

Shawn Doe says:

Thanks for the video. Is it worth it to insulate the basement floor with rigid insulation before putting the floor down?

wcndguy says:

I really like this method of finishing basement floors however I was wondering if you really need to use T&G subfloor for this and not just regular OSB. Correct me if I am wrong but I thought that the T&G portion of the subfloor was to ensure rigidity of the joint between floor joists. When sheeting over a solid concrete floor I don’t see the advantage of T&G. I may use your method shortly in the future, could I get away with using 1/2″ osb and maybe a couple of extra screws around the perimeter?

Joe H says:

Hi Jeff. I like your method but I framed my interior walls first. Is it possible to use your system (house wrap plus T&G 5/8 OSB) but keep the OSB floating? or does it have to be screwed into concrete? floating laminate is going over this. My reno friend suggested leaving the OSB floating.

Jeff Gruber says:

If you were to use the blue underlay without OSB, and just lay the laminate directly onto the blue underlay. Would you not put this under the bottom plates of your interior wall framing?

Inav Banz says:

My basement floor was dug in a few places to install concrete pads for support posts It seems that the concrete now seeps moisture year round at the junction of the new company concrete pad and the old basement floor. Seems like the concrete pads shrunk. Should I fix the water/moisture seepage first or simply install the dmx on top of the floor as is? Thanks.

Pample Moose says:

If you are drilling into the concrete and through your vapor barrier underlayment, haven’t you just breached/destroyed (and rendered useless) the moisture and vapor barrier and it’s effectiveness? Also, by drilling holes into the concrete haven’t you just opened up an easier way for water, moisture and harmful vapor (radon) to enter into the room?

As you can guess, I really don’t like drilling into the concrete floor however, I don’t want a “floating” floor that can potentially move around. I also do not want spots that can rise and fall when walking around on the finished floor either. (Where you can feel high spots that give way under ones body weight when walking around).

Please advise and thank you in advance for your help, knowledge and expertise.

Will Beames says:

During the video you mentioned not using 1 step when building walls as it would break the vapor barrier. Here’s my issue…… My basement is a 22×22 room in a split level house. The basement walls are approximately 4′ of foundation wall (lower) and 4′ of studs (Upper). The foundation creates a kind of ledge around the room. Also, I had a pretty significant water problem with ground water so I have already dug an interior drain and laid gravel, pipe and run it to another room with a pit and pump. However, the water is still seeping in through the cold joint between the footing and the foundation so my plan was to use the black DMX to line the foundation wall, down to the footing then fold it across the footing and over the drain trench so that it rests across the top of the gravel – then put 3″ of concrete over the top to match the height of the remaining basement slab floor. That way the DMX creates a barrier that channels any moisture coming in through the foundation wall and cold joint, down to and across the footing and under the concrete, into the drain and out to the pump. That said, I then wanted to use the 1 step on the whole concrete floor before I put studs against the foundation walls so that the 1 step would run beneath the base plates up to the foundation walls that have the black DMX on them. Can I do that and maintain a moisture barrier by tuck taping the seams where the one step meets the black DMX ? (ie, where the floor meets the walls) I really don’t want to go the full black DMX and T&G OSB route. The holes I drill through the base plates and secure with tap-cons or similar would be pre-filled with some sort of caulk as an extra barrier.
Lastly, the ledge, can I just use a 6 mil vapor barrier along the ledge so it hangs down the foundation wall and tucks behind the black DMX – rather than using a lot of the DMX up the wall and over the ledge ? Seems wasteful to do that. I would tack the 6 mil along the bottom of those upper studs.
I don’t see a way to just use the 6 mil from the studs and down under the concrete as there will be limited gaps for the water seeping in at the cold joint to escape to the drain and I’m worried it could all fail. I figured lining the walls with black DMX maybe 12″ up the walls would be sufficient with the 6 mil the rest of the way up to the ledge and studs since there’s no evidence of water actually coming through the foundation above the cold joint. Great videos….very informative. Thanks !

adiadiadii says:

What about a basement bathroom? Would you install this underlay under the basement bathroom as well or not? Thank you sir.

Logan Chen says:

What is your opinion on expanding basements? Do you think it is worth the money (normally runs around 70k usd from what i see around here)

Love Life says:

Is chip board or osb better for sound proofing please

Zak Shack says:

First of all, thank you VERY MUCH for your instructional video series Jeff. They have been a Godsend on more than one occasion now! I have a quick question… I am in the middle of doing a
combination of this video AND framing in a basement room door jamb. Basically I’m laying DMX
Airflow in a new basement bedroom with insulation and a metal stud
frame, up against already in place concrete block walls. I then have
3/4″ T&G OSB over the underlayment, and now I find myself literally
up to the doorway. Basically, I am wondering in this situation, do I
construct the door jamb ON TOP OF THE DMX AirFlow (in this opening), or
JUST OUTSIDE of the DMX, and on the concrete directly (using treated
lumber for the base of course)? I can’t help but feel that if I install
the jamb ON TOP OF the DMX, that I would effectively be trapping either
airflow into, or out of the room because of how snug the door jamb
would sit on top of the underlayment? Do you, or does anyone, have any
suggestions on this? Thanks very much in advance! Jason Paluszak

2732hill says:

Wonder if I can lay radiant tubing on top of that? Also I can’t find the tuck tape at my local building supply house in northern VT

Rob From Oak says:

The DMX AG (the black roll) is not recommended for indoor use – that’s what the manufacturer says (on the label). Is there a reason they say that except it’s cheaper by square foot and they have other products more expensive for indoor applications and they want you to buy them instead?

hazelwood55 says:

Here is a much better product.

KM says:

After finishing up with tile or wood floor what will happen when basement get flooded.

Kieran Fleming says:

Should I paint the floor first with a waterproof concrete paint to prevent moisture from exiting the concrete?

ItsInTheDetails says:

He does things the right way! Good job

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