Wavy appearance / waves on hardwood floor

Q: My hickory 4-inch-board floors were installed in December 2005 in a brand new home. The boards are not laying completely flat. They have a wavy-like appearance and you can feel the waves with your hands. I noticed the waves on hardwood floor probably a month or so after installation. I have been waiting, thinking they might flatten out in time. Also, I hear loud “cracking sounds” coming from the flooring from time to time. Could you tell me what caused this and if there is anything that can be done about it?

A: It sounds to me that you are describing “cupping” where the edges of the boards curl or raise. This is an indication of a moisture issue. The boards are expanding from excess moisture and pressure. Is this floor installed over a crawl space? I would do 2 things at this point. Go to your nearest electronics store and purchase a little device called a hygrometer, which gives you the temperature and relative humidity of the room. Place it on the floor for an hour or so to get a reading. Run a dehumidifier. If you had a moisture meter, I bet the reading of the floor would be over 9%.

Follow-up Q: The floor was installed over a poured concrete basement. The floor was installed in December, though, and it was not very humid then. Will it ever flatten out or will I just have to live with it? I doubt that the installer would do anything about it or maybe he couldn’t. I had been running the heat and air, however I live in Atlanta, Georgia area and it does get hot and humid here. I will buy a hygrometer and see what it registers. Will the dehumidifier make the boards lie flat again? I have a dehumidifier in the basement, but not the main floor of house where wood is.

A: One never knows for sure if a floor will flatten out. But the sooner you get on it and remove or expedite the transfer of moisture, the better are the odds.

Historic floods and hardwood floors

Q: We have a new wood floor installed in a new addition, over a newly built crawl space. The floor was installed during a very wet period of the summer (historic floods took place near that time). The floor was flat after finishing. We covered it with drop cloths for a few weeks while trim work was done. When we removed the drop cloths, the floors had cupped. There had also been a problem with drainage that the builder had fixed, but not before it flooded the new crawl space. Now we are stumped – the job is done, we are about to have it inspected, and the builder is saying to wait until winter for the floor to flatten out with the heat. What if it doesn’t? What if it still needs to be resanded and refinished? Whose responsibility is this? We are reluctant to move into the space before this issue is resolved, but how long can/should we wait?

A: It seems obvious that the water source is not in question. I don’t think covering the floors with drop cloths for a few weeks was a very good idea since it would not only slow down the curing of the finish, but may impede the normal transfer of moisture that does occur with wood.

It may well have cupped in any case, given a substantial amount of water under the crawl space. I think efforts should have been made to ventilate and dry that area as soon as possible.

At this point, it really is important to allow sufficient time for the wood to adjust and it is possible that it will flatten out once the heating season begins. The problem is, if you sand the floors too soon, they may bend the other way or crown. I think you need to have an agreement with the contractor that if they don’t flatten out during the winter, he will have them re finished. I know moving into the area and then taking everything out is aggravating. But at this juncture, time, ventilation and warmth are the only friends you have.

Humidity issue

Q: We have recently bought a townhouse in BC, in a forested area. We installed white oak, natural, prefinished wood from China. Everywhere I read, it talks about humidity needing to be around 40—50%! Humidity in our townhouse is never that low! It is probably closer to 60%, but depends on the time of day. Early morning can be 90% outside. Problem is, we would have to close all our windows, and bake – average humidity in our area is between 68 and 95%. They have only been in for a couple of weeks, and we are seeing some small separation between boards, but not a whole lot… nothing scary!

How seriously do we need to take the humidity issue? (Of course, no-one told us about this when we were looking at hardwood as an option.) We mercifully don’t have a leaky condo. Do we really have to forgo fresh air?

A: The humidity issue seems at times to be impossible to comply with in certain environments. For example, we are told to keep the RH in our homes somewhere in the range of 40-55%. If I did that in winter here in Toronto, I would have rivers of water running down my walls and windows.

I think the main thing you want to do is take the flooring onto the job site a week or so prior to installation. Make sure the flooring and sub floor are within 4% of each other. If you install the flooring at your typical living conditions, you should not have serious issues with either expansion or contraction. If it is typically 70% in your area, then acclimate the wood to that and install it. Try to keep the home within 15 points of that, either way.

I do have misgivings about buying these Asian floors. You never know what you are getting. If the milling is not good, or if they have not dried it properly, who are you going to get to support you? All this, not to mention that since these products are cheaper than what is produced here, in spite of being shipped all the way around the planet, I wonder how much the workers are getting paid at the point of manufacture?

Sorry I had to inject that. Just thinking “out loud”.

Wood flooring in a cabin in the mountains

Q: We are building a cabin in the mountains and I am looking at possibly installing in hardwood flooring. We will not be in the cabin during the winter and there will be no heat as we don’t have electricity. Would hardwood flooring work in a situation like this and if so, what type of wood?

A: Good question? I would think any wood floor could work provided there is not excessive moisture coming into the cabin. You might be better off going with a well dried soft wood and finish it with tung oil such as Waterlox. I would take it into the cabin and leave it sit for as long as you are able.

Moisture in excess is an enemy of wood

Q: I just purchased a condo with hardwood floors that were installed about 3 years ago. It is summer in Chicago and it is hot and humid. The central air has not been on in the condo so far this summer so I am assuming that the floor has expanded about as much as it is going to. I see cracks in between some of the planks and in some corners the quarter round moulding does not cover small holes in the floor. The cracks between the planks do not bother me aesthetically. I am wondering if it is OK to damp mop the floor the way it is? Or is too much moisture going to get underneath the planks because of the cracks and holes?

A: Moisture in excess is an enemy of wood. I would purchase some approved cleaner from the local flooring store, such as Bona Kemi Pacific floor cleaner. That is the best way to go.

Could improper nail down of the sub-flooring be a problem?

Q: I had a pine wood floor with 5 inch planks installed in my home on May 22nd. The first problem I encountered was that the installer brought the wood into my home and installed it the same day. I keep the temperature of my home around 68-70 degrees. Within 2-3 days I had gaps wide enough to fix 3 to 4 quarters in them.

The installer agreed to come in and take up the flooring and replace it. They removed the flooring (except for the Master Bedroom Closets) and left the sub-flooring they installed. They dropped off the new wood this time and I made them leave the wood in the home spread out among 4 rooms for 16 days. After that they installed the new floor and came back 6 days later and sanded, stained, and put two coats of water base finisher on the floor.

Now is where the problem occurred. Within two days after the water base finisher was applied, the floors cupped in the two Master Bedroom Closets and the small hallway between them. When tested, the floor moisture was 65%. The rest of the room was around 6%. What could have caused this other than a plumbing leak? The closets back up to the bathroom and are opposite sinks…. (more details included in email)… When I bounce up and down on the flooring by the threshold that was removed, you can see the sub-flooring move up and down about an 1/8″. Could improper nail down of the sub-flooring be a problem?

A: Improper nailing won’t cause cupping of the boards. The only thing that will do so is excessive moisture causing the wood to swell and press against the boards beside it. It does not surprise me that the closet is near the washroom, and I think that must be where the cause will be found.

It was certainly a mistake to bring the wood in initially and install it the same day without allowing for acclimation. Did they also test the moisture of the sub floor to make sure it is dry before installing?

It sounds to me you have a leak or you have moisture coming through ceramic tiles in the bathroom…. something of that nature.

Climates and wood flooring

Q: Does 3/4 solid hardwood flooring work better in certain parts of the United States?

A: You should be asking this question of flooring persons in the U.S. in certain extreme climates. I think solid wood is great anywhere, provided it is installed above grade and has been properly acclimated to the environment and installed on a properly prepared sub surface.

Related Q: I live in the middle of Florida. I have carpet right now and wish to know if wood flooring is acceptable for Florida climate. I keep hearing do’s and don’ts. What would the pro and cons be?

A: The main thing is to acclimate the flooring to the environment where it will be installed before installing it. Then try to maintain close to that relative humidity level in the home. If it is being installed over a concrete slab, you have to test first to make sure you don’t have moisture coming up through the slab. It is all about controlling the environment and moisture.

Flooring should always be acclimated before installing

Q: In January we had the carpet in our home replaced with hardwoods (four rooms). The new and older hardwoods were then all sanded and finished with an oil-base finish. Now, 6 months later, the new woods are cupping, not only in the rooms where there had been carpet, but also in the kitchen where new wood was used to patch a small area under a cabinet peninsula that we removed. Our first thought was that the cupping was caused by a moisture problem in the crawl space (we live in an area that is humid during the summer), but if that were true, wouldn’t all the hardwoods on the first floor be cupping, and not just the new wood? Does this have something to do with the installation? Acclimation? Finishing? What do you suggest we do to fix the floors? And can this be done without re-sanding and refinishing?

A: Flooring should always be acclimated before installing and both the floor and sub floor should be checked with a meter to make sure they are within 4% of each other on the moisture scale. Having said that, it does sound to me that you have a moisture problem that needs to be addressed first in the crawl space. I have seen floors that had cupped flatten out, so I would suggest you get someone in who has a moisture meter to check the floor. Buying a hygrometer is not a bad idea either. It will tell you the temperature and relative humidity in the air.

Related Q: How long does wood have to settle / acclimate in room before I install? Does it have to be removed from the package?

A: I would open the cartons and let it sit a week, but keep it away from heat sources. It is also a good idea to check both the flooring and sub floor with a moisture meter before proceeding. They should be within 4% of each other. The sub floor should not contain more than 4% moisture above that of the floor.

Related Q: How long should wood flooring dry before being installed? We live in Colorado, a very dry climate and understand most oak comes from more humid climates. Is there a way to tell if the wood is acclimated to this climate enough to install?

A: I would have the flooring on site, in the rooms it is to be installed in for 5-7 days. If it is boxed, open the boxes. It is still a good idea to test both the hardwood and sub floor with a moisture meter prior to beginning the installation.

Another Related Q: If I purchase hardwood flooring from one of the warehouse stores, prior to installation, does it need to sit in the house to assume the climate in the house before installation? If so, how long? I’m considering Mesquite or Brazilian Cherry. Does the type of wood matter? Thank you.

A: I would have it sit in the house a week and check it against the sub floor to make sure it’s moisture content is normal.

Related Q: I have 2.25 unfinished red oak. The house is under construction and the back up electric heat is on a constant 55, because it will run the bill up until I get the condenser bought and hooked up. But I need to get the floor laid..

A: I think you should follow the rules and acclimate the floor to the living environment the house will usually be in, before installing it.

Humidity and cracks forming on the wood boards

Q: I installed pre-finished floors in my kitchen, family room, and entry way about a year and a half ago. They were installed over plywood which was over concrete. There was a moisture barrier put down as well. I have been noticing cracks slowly forming on the wood boards, especially now as we are transitioning from winter into spring. It seems like the cracks start somewhere within the board and somehow get to the surface and bubble up the finish. The cracks go with the grain. In all your answers, you say that the cracks are due to lack of moisture. Could the cracks also be due to too much moisture? I bought a hygrometer and put it on the floor and the humidity in those rooms run between 55% and 65%. I think in your answers, you said the relative humidity in the air should be between 30% and 45%. I’m just not sure if I should add more moisture in the air or take out moisture.

A: This humid question is a sticky topic. If you read the advice of floor manufacturers, they will give the figure, likely of 45% relative humidity. However, where you live can dictate what to do. If I kept the humidity in my house at 45% in the cold winter, with furnace running, I would have condensation running down the windows.

I think the most important thing one can do is this: you know your environment and how humid it will be throughout the year. Install the flooring at the average and try to keep it close to that in your home throughout the year if possible. Also, make sure the flooring is in the home at least 5 days before installing so it can have a chance to adapt to the environment. If flooring was brought into a home in a high humidity environment, measuring, say 9% relative moisture content and you had high humidity outside, say 70% and the floor was installed immediately, it could expand after installation and cup, especially if no gap was left on the outside walls. If the humid condition dropped significantly, the floors could then shrink, leaving gaps.

In the above case, excessive moisture caused gaps because it caused the boards to swell, pushing against each other and moving each board just a little, then shrinking. This however, usually includes cupping of the boards.

Moisture content

Q: We installed our hardwood floors in Nov-05 and about six months later the floor started lifting. I had a gentleman come and do a moisture test and he mentioned the moisture should be 14% or below my moisture was at 25%. We have pulled all the floor up again and are wanting to redo it but can you please suggest what an individual can to put on their floor if there is moisture?

A: Normal would be 7-9%. Your floor is soaked and that amount of moisture has to come from someplace, and I suggest it is not from the air. It sounds like you have a leak someplace, and you will have to fix that first. The sub floor will have to dry out and before a new floor is installed. The sub floor and finished floor have to be within 4% of each other relative to moisture content.

Aired before installed

Q: Does pre finished 3/4 – 2 1/4 birch wood have to be “aired” in the house before being installed. If yes, how long? Individually or just open the cardboard box on the ends?

A: All flooring should be acclimated to it’s new environment 3-5 days before installation begins. Yes, open the box ends. I am sure I have read someplace to crack open all bundles/boxes of wood etc., but in practical terms that is impossible in most homes. Set the wood in the rooms where it will be installed, but not in front of operating heat vents. Make sure to check the moisture content of the sub floor and reference that to the hardwood being installed. There shouldn’t be a difference of more than 4%.

Hurricanes + humidity and wood floors

Q: I’m considering putting 5″ maple engineered floors on the 2nd story of my house (plywood subfloor). But I’m worried that when the power goes out for a week of two after a hurricane the humidity in the house will cause the floors to be ruined. If so, will they come back to normal? Also, is engineered flooring much better resistant to buckling etc.? Is there a particular species of engineered wood better then another?

A: I’ve never been to Florida, nor suffered a hurricane…thankfully. However, a few tips might help. The best engineered floor I have ever seen or worked with is Mirage. Engineered flooring is designed to be more stable than solid wood, which is why it is fine to install below grade also. If you follow the installation recommendations, and leave a small gap between the last board and wall I don’t think you will have any problem with this floor. I would give you a word of caution. The wider the board, the greater the chance of cupping, especially due to excessive expansion. Some species are more likely to react badly with humidity fluctuations than others. Maple is one of these, and you are thinking of a very wide plank. I wouldn’t go wider than 3″ or so and would likely stick with oak. White oak, quarter sawn would be most ideal, since it is most stable on side to side expansion.

Gaps for expansion

Q: I am in the process of renovating my house. One of the improvements is the addition of pre finished “Aztec Cherry” floors. I had a few people helping the day that we started the floors. The guy that had experience installing hardwoods was working on the 1st room while I was working on something else. This room is roughly 10′ by 15′. My concern is that, he didn’t leave a gap on the wall that the first strip of wood went down on. For the two walls that the wood runs perpendicular to, some of the pieces were cut to leave 1/4″ for expansion, but some run right up to the wall. On the wall where the last strip was installed a 1/4″ gap was left. I am wondering if you think that this will cause problems in the future? Is there anything that I can do to correct this problem? Also, should an expansion joint be left in all of the doorways? I would prefer to have all of the wood seamless, but want to install it correctly.

A: This likely won’t be a problem unless you have climate control issues in your home with very humid summers. If that is the case, you could always remove the first or last row of boards and run them or new ones through a table saw. 1/4 isn’t really enough of a gap for 3/4 thick flooring. 1/2-3/4 is what some manufacturers recommend. Whatever, some gap should be left along the walls, just in case. I would not worry about doorways.

Follow-up Q: What about the boards that run perpendicular into the wall? Should I worry about those?

A: No. The wood only expands and contracts from side to side.

Nail holes and moisture

Q: We just had a 3/4 inch common white oak floor put into the addition of our house. It is way too dark and even after bleaching it is still too dark. We would like to have it replaced. How do we deal with any damage that may occur to the subfloor? Will air and moisture be able to come through nail holes from crawl space under floor?

A: The floor is only nailed down. I wouldn’t expect any damage to the sub floor of any consequence. If there are moisture problems in the crawl space, it will work it’s way through the plywood, nails or no nails.

Hardwood floors in bath and laundry rooms

Q: We are currently remodelling our home and plan on putting wood flooring in both our master bath as well as our laundry room. I know wood floors are generally not recommended for these areas because of water, moisture, etc. However, we are unable to be perfectly happy with any other flooring. Is there any particular species that would be able to hold up better than the others? Also, we are planning on painting both floors? Any suggestions?

A: I would suggest, if this is the way you intend to go, to install quarter sawn white oak. A bit harder than regular oak but more stable as far as side to side expansion/contraction. I don’t know why you would paint rather than have multiple coats of a top quality polyurethane applied. Maple would be good for painting because it is so smooth with tight grain, but it gets a little cranky if subject to fluctuations in humidity.

Severe cupping

Q: I bought a home in New Mexico (extremely dry climate) three years ago which had been completely renovated. The entire home had been installed with soft wood flooring. The subflooring I believe is wood with a crawl space under the house. I noticed this winter that the floor was severely cupping in certain areas (the onset of which appeared to be quite sudden).

Since moving into the house I have noticed that the house creaks very loudly which appears to occur more frequently during seasons with greater temperature differentials (cold nights, warm days). I’ve wondered whether the creaking is a sign of the house settling and therefore a possible cause of the cupping in the floors.

I did pull up the moulding along the walls closest to the most severe cupping and the there was absolutely no gap between the wood floor and plaster wall – in fact the floor looked like it was burrowing into the plaster along one wall and along the opposite wall was being forced downward so the plank had assumed about a 30 degree angle. I’ve just assumed the cause could not be due to moisture since we have been experiencing the driest winter in recorded history. And there has been no water damage to the floors or in the crawl space.

The only change I have made over the last year is have a wood burning stove installed. Are there other possible causes of cupping floors aside from moisture? Do you have any suggestions? My inclination is to create space between the wood floor and the plaster walls but am reluctant to do that before determining the cause of the cupping. Any advice would be greatly appreciated.

A: The only reason a floor will cup is from excessive moisture and lack of expansion along the side walls does not help at all. Your floor is picking up moisture from some place. I would definitely cut the floor back along the walls 1/2″ at least. A moisture meter and hygrometer could help you to know exactly what the environment is at the floors surface. The moisture source is likely from the crawl space. If the crawl space has a dirt surface, I would place heavy plastic sheeting over it and make sure it is cross ventilated.

Floor might level itself out

Q: Providing I cut back the flooring along the walls and address the moisture issue once I determine it (as you assumed the crawl space has a dirt surface and there was no intentional source built into the crawl space for cross ventilation from what I can determine) will the cupping that has already occurred level itself back out or will I have to level it manually (i.e.- sanding)?

A: The floor might level itself out. I would give it several months to determine if it will adjust itself. If you do have to have it sanded, make sure it is tested with a moisture meter first to be sure it has returned to normal range.

Separations during cooler months

Q: Two years ago we had our 30+ year old oak living room floor refinished. The results were excellent! We had the same guys install a new site finished oak floor in another room this year. The new wood was allowed to sit in the room for about 3 weeks this fall to adjust to the temperature and humidity characteristics of the house. A product that they referred to as liquid oak was used during finishing. I understand completely ( from the old floor refinishing ) that during the cooler months, separations will appear between planks and subsequently close with warmer conditions. My concern is that some of the separations in the new floor have a very jagged appearance. Both the finisher and I agree that this resulted from the liquid oak separating alternately on each side of the boards as the wood contracted. In a small ” test ” area, he used a putty type product intended to fill such openings. Would you advise applying this ” putty ” along all of the openings? Do you have any suggestions? Am I better off to see this through for a year of expansion and contraction?

A: I would see it through for a season. If the floor expands in summer, what is going to happen to the putty? I would suggest trying to maintain in house humidity to between 36-42% in winter. You may need to buy a humidifier and hygrometer to keep check on the environment. I have not heard of this particular finish. Some coating will stretch a bit.

Install hardwood in basement

Q: I would like to install hardwood in my basement. I understand the moisture problems with basements, is there not a product out there that would seal the cement making it water proof? I was thinking of an epoxy paint, like the one they use on garage floors. Would this stop ground moisture from penetrating the concrete? I would then use a plywood subfloor prior to installing the hardwood.

A: I would not suggest a paint, as it may also interfere with a proper bond with the adhesive for the engineered floor. There are numerous products on the market that serve to retard moisture. One such can be found at www.bostik-us.com. Follow the hardwood flooring links for bostik products to the surface preparation link. You can even watch a video telling us all about MVP sub floor treatment. Don’t forget to make some popcorn! Perhaps a less expensive approach would be to glue plastic sheeting (at least 4 mil) to the concrete using one of the Bostik adhesives which are all moisture resistant. Check all the data at the bostik web site.

Flooring glued to concrete buckling

Q: We have recently had a solid oak floor laid in our living/dining area. The floor consists of oak planks (160mm x 20mm) glued directly onto concrete subfloor. Unfortunately the floor has buckled severely in couple of areas. How do we rectify this matter without incurring huge costs? Will it go back naturally with the aid of a dehumidifier or would we have to replace the whole floor?

A: I am not sure why you elected to have solid 3/4 thick oak “glued” down, rather than having a sub floor constructed which could be nailed to, or else using an engineered product such as Mirage engineered that is designed for this sort of installation. Whatever the reasoning may be, the one element that will cause such buckling is moisture migrating into the hardwood floor. Either you have a leak or moisture is coming through the concrete. Did the installer check to see if the concrete was and remained dry, or was bleeding moisture?

You will have to correct the moisture issue first. You will also have to remove the damaged areas, remove the adhesive from the concrete as much as possible and proceed to install only when the concrete is dry and the moisture issue is solved.

Bostik’s Best or equivalent urethane adhesive is best for a project such as this. There are also products that can be applied to serve as a vapour lock. Using the proper size notches on the glue spreader is also important.

A dehumidifier won’t help you in this case because the adhesive is already cured.

Related Q: Approximately 4 months ago, we had engineered flooring installed in our home. Lately, we have noticed that in certain areas the flooring is releasing from the concrete sub floor. Would you know as to why our flooring is acting this way and if there is anything we can do to fix this problem?

A: Pretty tough to comment on that. I don’t know the adhesive used. I don’t’ know if moisture tests were done (though it doesn’t sound like it is a moisture problem). It could be something as simple as the wrong notches in the trowel to spread the adhesive. Did they roll the floor after installing?