How To Spot And Fix Subfloor Problems Before New Flooring

 How Do I Know If My Subfloor Needs Repair Before Installation?

Think your new floor starts with the first plank? The real story begins beneath the surface. We dig into the make-or-break decisions that determine whether hardwood, luxury vinyl, laminate, tile, or carpet look and feel right for years. From weather-battered subfloors in new builds to hidden surprises during remodels, we lay out how pros diagnose problems, set expectations, and keep your project on track without overspending.

Jason Trim, owner of BPS Southeast, joins us to explain why flat often beats level for most installations, and how a simple straightedge reveals the truth about humps and dips. We talk through real-world examples, including big-room fixes that require dozens of bags of leveling compound, and we share quick at-home checks anyone can try—like paying attention to subtle elevation changes as you walk or watching how a toy car rolls across a room. If you live in an older home, we outline why legacy materials flex more and what that means before you swap carpet for a hard surface.

Moisture is the quiet villain, especially on concrete slabs. Jason breaks down how water pressure can migrate up through porous concrete, causing musty carpet, cupping wood, and failed adhesives. You’ll hear practical strategies: use primers to lock down dust and improve bond strength, add vapor barriers where risk exists, and build smart prep allowances into remodel budgets so surprises don’t derail the plan. We also cover targeted wood subfloor repairs, from grinding seams to cutting out water-damaged areas around bathroom flanges.

If you want floors that feel solid, sound quiet, and stay beautiful, start with what you can’t see: the subfloor. Subscribe for more practical contractor insights, share this with a friend planning a renovation, and leave a review with your biggest flooring question so we can help next.

To learn more about BPS Southeast Flooring visit:
https://www.BPSSoutheast.com
BPS Southeast Flooring 
Servicing Rutherford, Polk, Henderson and Cleveland County 
828-532-2141 

Transcript

Why Subfloors Decide Success

SPEAKER_00 0:00

Before new flooring goes down, the condition of what's underneath can make or break the entire project. Welcome everyone. I'm Chelsea Earlywine, co-host and producer here in the studio with Jason Trim, owner of BPS Southeast. Jason, hope you're having a productive day so far.

SPEAKER_02 0:16

So far, we are enjoying the cool weather and hoping maybe we might get some snow in the early future this winter.

New Build vs Remodel Reality

SPEAKER_00 0:23

Ah, okay. Fingers crossed for some snow. Well, Jason, let's get right into things. How do I know if my subfloor needs to be repaired before installation?

Flat Versus Level Explained

SPEAKER_02 0:33

Well, in the two different types of projects you're going to be looking at, it's either new construction or remodel. So taking new construction, you can look at it during the construction process depending on the type of subfloor they had, and then also the amount of weather in that subfloor may have gotten. So sometimes getting the house dried in, it may have gotten a lot of rain. So sometimes the floors will start to get a little warped just because the amount of water it got onto it. So sometimes a lot of the crews will take a long straight edge, which is basically just a long aluminum, almost looks like a two by four, and it may be anywhere between six to ten feet long. And they'll set that on the floor just to see if there's any gaps when you're here and it's setting a little high and you can see under it, then you know that you're either gonna have to grind down a high spot or you're gonna have to fill it in one or the other. So that's the one things that you'll look at. On a remodel, you really can't judge it unless you've pulled the flooring back. So that's a tough one because in any remodel situation, we try to forewarn them that you may have some floor prep or things to deal with when we remove the flooring. Sometimes you know that there's damage because there may be a soft spot, or you may be aware of something making noise. Like if it's some tile and you know that the tile's making a little noise, it's cracked, or different things, you know there's something going on, but that's not always the case. So we've removed carpet, and then we find out that the floor is if they're putting hard surface in its place, it's got some really heavy low spots. I mean, we had a thousand square foot area that we ended up putting about 30 50 pound bags of leveling cement over different areas of the floor as a total, and that made it flat. But we weren't looking for level, so there's a difference between flat and level. Level is everything's perfectly. I mean, you can put a level on it, it's gonna look good. Flat means over a transition, there may be some slight variances, but it's within tolerance of the warranty of the product. So we try to get it within flat because sometimes level could be, yeah, you need to add at least a half an inch to an inch of cement raising this whole floor where it doesn't have any humps in it, and we can go with flat and still be within tolerance. So level floors are a lot more expensive than flat floors if you're trying to prepare them that way.

Warning Signs You Can Feel

SPEAKER_00 3:05

Oh, that's interesting. Okay, so are there some common warning signs that homeowners should look for?

Old Homes And Shifty Subfloors

SPEAKER_02 3:14

If it's on a concrete slab, which is normally your basements or some of your single-level homes, depending on where it's being built, uh, when you walk into a room, sometimes you can feel your body just kind of go up and down slightly. You can sometimes feel it, and also if if it's an existing floor, let's say a glue-down product, you may have sheet vinyl or something. If your children are playing on it and their cars kind of go in one particular direction and then stop, more than likely you got a hump in the floor that it's now in a low spot. So sometimes visually, you can play it just by children playing on a hard surface that you want to replace, you can see ups and downs. If it's carpet, it's a little more challenging because carpets can be real, it's thick, it's soft and absorbed, so you can't always visually see it because it's a it's a fabric that's designed to kind of blend, make the whole floor blend together. So it doesn't stand out. And people who go from carpet to hard surface, those are the ones it's really difficult to say because you typically run into uneven floors on either concrete or older homes. So say that the home is built between let's say mine's 1949, and then you go to let's say something into the 90s. Any of those older homes when they're changing the types of subfloors within the constructions, different types of products were used before standards were set. Some of those products tend to flex and move more. So older homes, the regulations were not as strict. So the subfloor products they used were not as strong or more as rigid. So you can tend to get more uneven floors out of older homes.

Wood Subfloor Repair Basics

SPEAKER_00 5:00

Hmm. Okay. So so Jason, um, when we're looking at the repairs, how do you how do the repair needs differ between subfloors and the concrete slabs?

Concrete Slabs And Moisture

SPEAKER_02 5:13

Subfloors typically are wood if it's anywhere often if it's not on ground level and it's not raised. So if you don't have a crawl space and you're building up, it would typically be wood. So the only damages that we try to take care of is if it's not flat, we can sometimes take grinders to where the joints are and grind it down. Because it would that you can you can pair it down with a grinder. You can also fill it in with a little bit of semen if it's some low spots. The worst issues is if there's water damage, we'll have to cut open and you never know what you're gonna run into if you're dealing with water damage. So if it's a bathroom, we had a leaky toilet, and you know you have some damage. Well, once you pull that toilet up and take the floor, and it could be not much just around the toilet flange, or you may end up ripping out half the bathroom floor. So water damage is something you'll never be able to really know until you get into it. Concrete slabs, the biggest issues that you'll see are uneven floors and water moisture problems. Because concrete is porous, you don't think of it as porous, but if the water does not drain away from your home, there's an there can be enough weight in water will actually push up through the concrete. And then if you have carpet, it makes your carpet smell musty, like that real moldy smell. But if you have wood or vinyl or laminate, it can actually cause those products to buckle and to come up off the floor, and you'll have to tear it open and then seal the concrete with a moisture barrier.

SPEAKER_00 6:50

Wow. Sounds like a lot of additional work.

Cost Buffers And Precautions

SPEAKER_02 6:53

It can be. If you're doing a remodel, we try to include all that information. So if we're doing a concrete so far, we put floor prep in as a blanket cost. So if we don't do it, we don't include it in the bill. But we also explain to the customer we could run into more than what this blanket covers. So we try to be very, we try to hit the worst possible outcome, but we can't always guarantee that. But if we're doing concrete, if we're doing carpet, vinyl, wood, we will tend to put a moisture barrier just for precaution, even new construction, because the landscape can change around a home. You can get heavy rains, you can get gutters that get clogged. A lot of factors can change where moisture become can become a problem. And then on wood floors, we try to make sure that the floors are sealed with a primer. Doesn't necessarily have to be a moisture barrier, but at least a primer so that if you're gluing a floor down, you get a good secure bond. If you're putting something down, it does it basically seals the dirt down so there's no loose dust underneath your flooring as well.

SPEAKER_00 8:03

Ah, that makes a lot of sense. Well, Jason, you are clearly the expert on all of this. I appreciate you walking us through this. It was very helpful information, and we will see you next time.

Primers, Barriers, Better Installs

SPEAKER_01 8:15

That's today's step in the right direction from the BPS Southeast Flooring Podcast. Ready to finally love what you're standing on? Call Jason for a free estimate at 828-532-2141 or visit bpssoutheast.com. Luxury vinyl, hardwood, carpet, tile, flooring for everyone. Thanks for listening. And remember, great rooms don't just happen, they're installed.