Why is engineered wood floor crowning?

6 years ago

In my recently renovated house, I used engineered wood flooring for the basement level in large part due to its ability to address humidity issues better than traditional hardwood floors. Installed by the same company that installed "regular" hardwood floors in upper levels. I've started noticing areas of what I believe is called "crowning" - i.e., the center of the board is raised up. Or it might be more accurate to say some boards seem to be very slightly elevated and when you rap on them, they sound more "hollow" than other boards.

Some of these problematic boards are in my wine cellar but before you suggest that the higher humidity levels in there have caused this, please note that the problem exists in the basement bedroom too, which I assure you is not humid. Also in my wine cellar, the front board the first stair tread is pulling away and so is the riser to which it attaches.

I am trying to figure out what is causing this so I can get it properly corrected. Any assistance greatly appreciated.

I'm attaching pictures.

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PRO

WeShipFloors

6 years ago

last modified: 6 years ago

Winonelson,

Yes, the top is expanding in size and the bottom is not. That's what causes the crowning. If the bottom were expanding and the top was not, you would have cupping.

In that wine cellar, I believe you'd need to bring the flooring, treads etc. up to that humidity prior to the install. You'd need to have a moisture barrier too, not to keep the moisture out, but to keep it in. Anytime you have a wide spread in moisture between the room and the subfloor, you're going to have problems.

Case in point: The largest flooring retailer in Knoxville TN used to be a very good customer of mine on the distribution side. They turn huge numbers, but they are terrible about installing flooring improperly. They would take prefinished solid 3/4" hardwood flooring out of their non-conditioned warehouse at 7 am and they would be nailing it down by 9 am that same morning. On one of the many claims they had, the entire house was cupping. This means the bottom of the floor was growing. While there inspecting the home, we found a open box of the product in their basement. Because this floor had not been nailed down it had plenty of time to acclimate properly. Even thought the rest of the house was cupped like crazy and sub-floor and basement had very high humidity, the un-nailed product was flat as it could be. When flooring get installed too quickly, it encapsulates the moisture. That moisture has to go somewhere. The wood soaks it up like a sponge. The bottom of the floor grows while the top does not and this causes the cupping.

Alan Ward
WeShipFloors.com
1-844-356-6711

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Comments (14)

PRO
WeShipFloors
6 years ago
If the top is growing (which it obviously is) your moisture levels in your basement are too high- in relation to the subfloor moisture. Did you do a moisture test prior to doing the work? Did the floor acclimate prior to install?
PRO
WeShipFloors
6 years ago
last modified: 6 years ago
As far as the tread goes...

I believe the board behind the one with the bullnose is growing, this is what has pushed the miter apart. It's hard to tell without being there.

You need someone to do some moisture testing on your project if you want to get to the bottom of what is going on.

Alan
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winonelson
Original Author
6 years ago
well, the pictures of the stairs are in my wine cellar. And it is certainly humid in there - that's the goal. As to whether there was a moisture test I cannot tell you - but I'll see my GC tomorrow and ask. He did say the subfloor (concrete) cured well over 30 days.
winonelson
Original Author
6 years ago
and by "growing" do you mean what I understand "crowning" to mean?
josephene_gw
6 years ago
Take out the humidity and it will level off. You have a foam substance

under the very thin layer of wood, right? The foam grows when damp/wet.
PRO
User
6 years ago
last modified: 6 years ago
This may sound redundant but the crowning you are experiencing is from moisture. The moisture content above the hardwood is higher than the moisture below the hardwood(i.e. the subfloor) The proper Relative Humidity(RH) for hardwood flooring is between 30-50%. Some say that 40-60% RH is OK. Anything higher your flooring has the risk of buckling. Even if the humidity doesn't seem that high in certain rooms- it may actually be. I would invest in a RH reader. They sell them on Amazon and we had purchased them for many clients.

Moisture Reader on Amazon

If you click on the link above- it is the moisture reader we have purchased. It reads the temperature and moisture content in percentage. It also has a gauge which will tell you when the RH is low, high or just right.

Cupping vs. Crowning
PRO
G & S Floor Service
6 years ago
Was this a glue down, site finished floor? If, yes, the flooring was sanded to early. The moisture in the wood did not return to the original reading prior to installation. The floors were sanded, then drying was completed afterwards, leaving you with crowning. Repair will depend on the thickness of the veneer.
SJ McCarthy
6 years ago
How was the flooring installed? Floating or glue down? If glue down, what glue was used? How long did this have to acclimate in the SPACE (with all humidity ranges set at the appropriate levels, etc) BEFORE it was installed? How much expansion gap was left at the walls? Can you pop off some trim to measure it? Photo of the measurement?

Wood happily expands in the presence of moisture. It is hydroscopic. That's what it does. That expansion/contraction is supposed to happen BEFORE the installation. That's why the acclimation in the CONDITIONED space must happen BEFORE the floor is installed.

When you pop off the trim, you can do a quick guestimate to figure out if enough expansion was left around ALL vertical obstacles (door jams, walls, corners, etc): the expansion gap is often the same as the THICKNESS of the floor.

That means: a floor that is 3/4" thick plank (19mm) should have (roughly) 3/4" expansion gap (19mm). A 1/2" plank should have 1/2" expansion gap. This is a rough estimate of what is needed. You get the idea. Go ahead and pop off some trim and measure the gap.

What is the humidity reading in the wine cellar and in the rest of the basement?
winonelson thanked SJ McCarthy
winonelson
Original Author
6 years ago
well, my GC and his flooring guy are supposedly meeting me at my house in the morning. I've sent the explanations above to my GC. Not sure what he will do. Part of the issue in the wine cellar is that the racking is installed above this floor and it's full of wine! (A picture of part of the space is below.) I guess I could let the humidity go down some (it was hanging out at 70% this summer - that's ideal for a wine cellar). Frankly, I wanted to put in a cork floor but my GC said the engineered wood would work in there.

If the humidity drops to closer to 50%, will the boards retreat to a proper shape or do I still need to have remedial work done? And I'm curious about what is causing the problem elsewhere in the basement, where it's not nearly so humid (probably well below 40% now.)
winonelson
Original Author
6 years ago
Oh, and when I get home I'll check the humidity levels at present and report back.
PRO
G & S Floor Service
6 years ago
Is the issue only in the wine room and bedroom? Or is it consistent throughout basement?
PRO
User
6 years ago
First, your wine cellar is absolutely beautiful. Some can only dream of having a space like this in their home. Simply stunning.

How is the flooring cleaned? I'm asking because maybe that is one of the culprits causing this issue in the other areas of the basement. Maybe there is too much moisture being applied to the floor. It's hard to definitely tell what is causing this issue without doing a proper walk through and looking at all check points.

If the humidity drops, there is a possibility the flooring will retreat to normal condition. But there is also a possibility that it won't.
PRO
User
6 years ago
SJ McCarthy makes a valid and strong point, definitely check if there was proper expansion space left. Good Point.

Why is engineered wood floor crowning?

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