Cracks and boards separating after overheating dried out floor

Q: While away from home recently for an extended period of time, a power surge caused our electronic thermostat to malfunction and the heat stayed on continuously for what may have been as long as 2 weeks. Because of that there was extensive damage throughout our home, especially to our hardwood floors which contracted to a point where walking on them without footwear is painful. The cracks are large and the boards have pulled away from the walls.

I now have a humidifier running and hope that in the coming months the floors will expand enough to close the gaps. I have noticed that because of the large gaps, not all of the boards are staying level. Do you believe they will they expand enough to close the very wide gaps? Will we experience warping when they do expand?

A: I don’t know what is going to happen. I’ve seen floors that got soaked, cupped and heaved and then later settled down to the point you could hardly tell there had been an issue. Your problem is exactly opposite. I don’t think they will cup and they should expand.

I think you need to set up a humidifier in a lower level, below the floors. This way the increased and correct moisture will rise and go through the bottom of the floor and work it’s way through the wood. If you had a moisture meter you would better be able to monitor the actual moisture content in the flooring, which generally is 7-9% for normal readings.

Good luck with it. I guess when possible, it is a good idea to have someone check in on the house every few days if we are away for an extended period.

Related Q: We just put in a new red oak floor in about two months ago. The weather was warmer and now we are in the middle of winter. The whole floor is separating. We are wondering if the boards were tight enough or if the wood was seasoned enough. The wood sat in our house one week before being installed. Does wood have to be seasoned for a period of time prior to purchasing? What else would have caused this?

A: You need to raise the humidity levels in your house. The floor may have been acclimated to the climate in the home at the time. However, if for example you don’t have air conditioning and you don’t run a dehumidifier in the summer, and the floor was installed with, say, 75RH in the home, then if it drops to 27% in winter with the furnace running, that is quite a difference.

I would buy a cheap hygrometer to keep an eye on the temperature and RH in the home and invest in a good dehumidifier. If you could find one that does that plus dehumidify that would be a bonus. Try to get it up close to 40% in winter. The gaps should close up or at least ease.

Spots where wood is cracking along the grain

Q: I have been in my house less then a year. We have distressed oak floors with a lot of character, which is fine, but there are numerous spots where the wood is cracking along the grain-enough to catch a sock.

Were they not finished properly? Another sanding and coat of polyurethane needed?

A: Cracks developing has nothing to do with the sanding. The boards were probably “defective” before they were installed and then with dryer conditions inside the house they may have shrunk a bit and the cracks revealed themselves.

You can either have the boards changed, or something you might try is injecting some type of adhesive into the fissure to stop it from opening further. If the adhesive dries below the surface you can then fill up to the top of the board with colour match wood filler. Try not to get the adhesive on the surface of surrounding boards. Cyano-acrylate adhesive may work well in this instance. It dries clear.

Related Q: Our newly installed hardwood floors have a plethora of deep cracks along and through the grain of the boards, which one can see from outside the room in multiple boards; some cracks are extended through the knotholes in the custom cut combination #1 and #2 Red Oak hardwood floorboards and seem to extend through the thickness of each board.

Should we allow the installer and contractor to do as they have proposed and re sand and fill the cracks and then apply another coat of finish, or should the custom cut hardwood floor system be replaced?

A: Not surprising you have so many split boards given the low grade of the oak. I would recommend replacing the bad boards and then sanding over. Sanding and filling won’t make the deep cracks disappear.

Filler is old, dried out and falls out easily

Q: We recently bought a Victorian farmhouse that has wide-plank pine floorboards. The boards have gaps that have been filled once, but the filler is old, dried out and falls out easily. I would like to re-do the filler, but I’m not sure of the best product to use. Any recommendations? Some gaps are quite wide, up to 3/8″ wide. I love the look, but it’s drafty on a windy day and I want to re-seal them.

A: I’ve use a number of wood fillers, but they all will crack and pop out eventually, especially so if there is movement between the boards. Even vibration can cause it to pop out. With one pine floor which had large gaps, I packed the gap with rags twirled like rope and applied some expanding polyurethane adhesive. (rope or other alternative could be used) After that dried, I sliced off any adhesive that expanded out of the gap and then filled on top with Timbermate which is a more robust filler. It is expensive and difficult to work with because you have to keep mixing water with it. No waste with the product though, which is one of the good things. Be aware that if you don’t plan to have the floors sanded, you will need to tape off the surface of the boards along the edges of the gaps so the expanding adhesive does not get onto the face of the board. One thing for sure in using this method: it won’t fall out and it helps to stabilize the boards against movement.

Related Q: We refinished an old wood floor. There were a lot of little gaps between some of the planks, so we filled them with wood putty, then stained and polyurethaned. Now we notice that a lot of the putty is popping up through the floor. What do we do? Can we sand what’s above floor level and re-stain and poly again? What do you suggest?

A: Which brand of wood filler did you use? The way this is suppose to work is the gaps are filled, sometimes more than once to bring it to the level of the floor surface or above. When it has dried this all has to be sanded off flush with the floor surface. Staining is done after this. If you are saying that the filler is now being pushed up this means the floor is expanding from excess moisture. This could be from high humidity or perhaps from water in the filler itself. You have already finished the floor. I think I would cut the excess off with a razor knife carefully, then buff and coat if needed.

Similar Q: There were gaps between some of the floor boards in my home, which a flooring company repaired with a wood filler. The filler has already cracked and it looks as if the edges of the hardwood floors have cracked with it. What is the best solution for this problem? How best to remove the old filler?

A: Gaps as wide as a dime are considered by the National Wood flooring Association to be normal. Of course, good climate/humidity control and proper acclimation of the floor before installing will go a long way to minimizing gaps. It should also be noted that some wood species are more susceptible to gapping than others.

From what I’ve found to date, all wood fillers will crack if there is movement between the boards. Removing it is tedious and may result in some chipping of board edges. You could simply run a thin screw driver inside the gap and suction out the pieces of filler. At times you may have to tap down on the filler to break it away from the board edge. A razor knife may also help in removal. Perhaps a better solution on larger gaps is to mostly fill the gap with an expanding polyurethane adhesive and when it cures, use wood filler to top up the gap flush with the floor surface. A word of caution however: Moisture can exert a lot of stress on a floor. If humidity readings and moisture readings in the floor are high the wood is going to expand and push planks over. After the moisture level drops the boards will shrink. A very strong side bond created by the adhesive could cause a problem called panelization where the floor gaps in sections. Best solution is to control indoor humidity or accept that floors are an organic substance and will move with the environment.

House — ceiling, stairwell — is cracking

Q: A week ago we installed hardwood flooring on our main floor. 2 Massive cracks have developed: first in ceiling, and then an even larger crack appeared going up the stairwell above the new flooring. Is this common? We will have them filled and repaired, but I’m concerned. Thank you!

A: I don’t know what the relationship could be of having a hardwood floor installed with cracks in the ceiling or up the staircase. If this is a new house perhaps it is still drying out. If this is the case, I hope the installers checked the sub floor for moisture first.

Splits on edges of board due to wear

Q: We recently had some oak engineered flooring installed and have noticed two small splits at the very edge of one of the boards. I think they have steadily gotten worse as they sit right near a door threshold, which is a high trodden area. Can it be repaired or will we need to replace it? Thanks.

A: You could use some colour matched wood putty to simply mask the cracks. A good product is Color Rite. Comes in tubes. Dozens of choices and easy to work with. If the split get serious then of course the board will have to be replaced.

Glue down hardwood floor separating at joints

Q: My parents had hardwood floors installed in their home a little over a year ago. They live in a home that is about 8 years old and the 3 rooms that had the flooring put in all had carpet in them previously, which was properly removed. Then the floor was levelled. This weekend the flooring started separating at the joints, in random parts of all 3 rooms, which are in different parts of the house. The installer is a friend of mine and he had never seen or heard of such a thing. The flooring was purchased from my work, and when I spoke to the decorator here she said that it has to be an installation problem. The installer knows he used the correct type of glue, but have you ever heard of a floor doing this after being down long? The house has no structural issues.

A: This floor is glue down? It sounds like the sub floor is shrinking and the glued down floor is separating at the sub floor seams. I’ve seen it only a few times in 40 years, even on very old floors. It stands to reason, the finished floor will react to what the sub floor is doing. I would put a moisture meter on both the finished floor and sub floor if you have access to that. They should be within 4% of each other. You may also check the humidity level by placing a hygrometer on the floor for a short time, say 15 minutes. I feel fairly confident the issue is the sub floor itself. What was used to level the floor? If water was added to the sub floor along the joints (I assume it is sheets of something) it may have expanded and then as it dried it shrunk.

Filling large gaps in wood floor

Q: I live in a 200 year old house that was nicely restored about 40 years ago. Our living room has a pine plank floor, which was finished in shellac (I think). The boards have separated over the years and there are large gaps ranging from 1/16″ to 3/4″ of an inch. Since the boards go under the walls there is no way to lift and move them. I also don’t want to refinish the floor, as it is rather striking as it is. What was in the gaps previous seemed to be a mixture of clay, sawdust, hair, and maybe glue (very old-timey). I have cleaned all of this out.

My current strategy is to fill the large (3/4″) gaps with a strip of wood (dyed and finished to match), and use dyed hemp rope in the medium sized gaps. I might use dyed hemp rope for the bigger gaps as well. If you have any other suggestions, I’d be grateful. I also wonder if there is something to put in the smaller gaps that won’t require refinishing the boards.

A: It sounds to me you’ve got a good grasp of how to take care of these gaps. As for the small ones, there are numerous coloured fillers in jars and tubes you can search out. Push it into the tiny gaps and wipe the residue off the surface with a damp cloth.

Related Q: I need to repair large gaps, in seams in several spots, in the old hardwood floor of our upstairs bedroom. These are bad enough (about 1/2″) to allow any liquid to drip through and down to the ceiling of the 1st floor. I had planned to mix sawdust and Elmer’s glue, let it harden and sand it level. Any comment or suggestion would be appreciated.

A: I would likely try some version of your suggestion, except I would probably use Gorilla polyurethane adhesive or equivalent. You would have to stuff something into the large gap to hold this adhesive until it starts to set though, so it doesn’t just run through to the ceiling. Also, you would have to apply painters tape to the boards on each side of the gap because this adhesive expands as it cures and you don’t want it all over the surface of the floor.

When it has dried, cut the excess off with a knife, preferably to below the surface of the floor. Then use a colour match wood filler to just glaze over the top so it doesn’t look too obvious.

New wood floor splitting

Q: We moved into a new home. Our oak floors are only 1 year old. In their first year there have been dozens of splits in several areas of the main floor. What causes new wood floor splitting? We have an HRV that runs all the time and the humidity is 40%, constant.

A: I would say your humidity levels are near perfect as can be. However, you say this is a new home. To me this is a clue. I’ve worked in houses being built. It isn’t pretty! The structure is suppose to be dry and the floors acclimated before installation but often that is not the case. And so, everything is rushed and over months the sub floor and finished floor continue to shed moisture and shrink. Certain cuts of flooring are more prone to getting splits such as quartered and rift sawn. It may be the cracks were present in the boards at installation but were not noticed. As the floor dries and shrinks they appear! Ideal at installations is 7-9% moisture in hardwood and not more than 4% difference between it and the sub floor.

Follow-up Q: Thank you for taking the time to respond. That’s what my wife and I thought. It may be because the builder isn’t owning up and said it’s on us. We’re just trying to find as much info as possible. Is there any else that could cause this? Thanks again.

A: Well, wood and wood products will react to environmental conditions. I don’t see a thing wrong with the humidity levels you hold. I live in a fairly cold climate and in winter 40% would be the upper level I would recommend in a house without creating condensation issues. When I lived in —— I was asked to look at pre finished floors in a sub division in Welland. The floors were all cupped. Clearly the structure was not dry when the floors were installed. Terrion, the warranty company and the builder said this condition was acceptable within their standards! It’s a load of crap in my view but how can you fight it without it costing more than the floors and enough stress to bring on cardiac arrest? I suspect the system is set up that way. Kind of like getting a ticket and to fight it will cost more than the price of the ticket. When it comes to new construction, builders usually have different price packages. I would tell someone go for the cheapest and do upgrades with private, personally chosen contractors after you move in. That way you avoid the huge builder mark ups and get personalized service. I know that is too late in this case.

Related Q: Hi. We built a house last year and had wood flooring fitted on top of UFH. Within the last 6 months the solid floor has started to split. We currently have 70-75% of the floor showing cracks, some of the cracks are quite large. The UFH was all fitted correctly with no problems. Any ideas why this might be? I’m not having much luck with the company who fitted it. Thanks.

A: Possibly the flooring or the milled wood used to make the flooring was not properly dried. Are you also getting gaps between boards? I would definitely press the installation company to come back and have a look. I would also find out who the manufacturer of the floor is and contact them.

Follow-up Q: Hi, thanks for getting back to me. I have tried contacting the supplier, but they don’t deal directly with the public. I have got gaps but nothing substantial.

A: Wood will always react to it’s environment. I think your floor is drying and is thus presenting some cracks. Honest business practice would say somebody should come back and at least look at it and take some moisture readings and give advice. I will suggest you contact the National Wood Flooring Association as a last resort. They have a lot of expert advice and have trained people who may be in your area to come in and evaluate this problem.

Q: Our pre-finished floors began splitting shortly after installation. The floor boards are continuing to split with the grain of the wood. We were told the installer used too many nails.

What would be the proper fix for this issue? A complete re-install or just replace the splitting boards?

A: I would replace the splitting boards. I don’t think it is possible to use too many nails.

Have you checked the RH in your home? Perhaps it is too dry. And it could be the boards had hidden fissures directly from the mill that only opened up after they started to adjust to the climate in your home.

Poplar floors have cracked, gapped, and some planks slightly cupped

Q: Problem- Floors have cracked, gapped, and some planks slightly cupped.

Floor Description: 3/4″ Thick, 5″ wide new poplar floors, installed fall/2008.

Finish: A water-based polyurethane finish was applied to unfinished boards after installation.

There is a full size, unheated basement below the floors.

Humidity readings we started taking in late winter of 2009 have run consistently between 40 to 50 percent.

Our contractor has contacted the poplar flooring supplier who said he does not guarantee his lumber. I was not told this when I bought the planks.

Our contractor has said there is nothing he can do. He explained (which we already knew) what would have to be done to replace the floors: moving furniture, ripping out baseboards, damage to dry wall, etc. Needless to say we are talking about a huge expense. Additionally, he said he couldn’t replace the cracked/split planks, as they are tongue and groove. He also stated the cracking may happen again with any new planks. We are not willing to accept this non-solution as it has greatly decreased the value of our home, not to mention how it looks. Last year when I talked to him about the floors again, he said the cracks just make the floor look old.

I need to know what I should do to pursue this issue, as my contractor is not interested in seeking further information in helping solve our problem.

I was 3 hours away taking care of sick parents the majority of time the contractor was installing our floors, so I do not know how they installed the floors. I do think they placed paper on the subfloor. The contractor said they protected the planks prior to installation. I do know they cut the planks outside as they installed the floor and I know they did not take lumber back to the basement at the end of the day. I also do not know if they allowed time for planks to acclimate to the environment. I do not know if they checked the moisture level of the planks or the sub-flooring prior to installation. How should they have installed the floors? Adhesive? Should floors have been nailed or stapled?

The contractor has stated he thinks this would not have happened had I used an oil-based polyurethane finish. I question this, as the supplier I purchased my finish product from is reliable and has not had this problem occur.

Another interesting observation: The floors installed in the first two rooms have not cracked.

Bottom line, our contractor has basically walked away from the problem (both literally and figuratively). We have had a leak in our ceiling originating from the bathroom vent, and he has not returned to fix it since we revisited the floor problem.

Should we, the homeowners, be financially responsible for this problem? What steps should we take to investigate the problem? Call in a floor specialist to look at the floors?

We live in a very small community. Finding resource people is difficult, as we live 2 to 3 hours away from a major city. We do not want to get into litigation.


Many thanks for responding to this problem.

A: I’ve never worked with poplar flooring. It isn’t very common, at least not in Canada. I have read however that it is subject to checking and splitting during drying. These boards probably already had splits in them which went unnoticed during installation but opened up after finishing which is a common occurrence. Everything you have described to me is a moisture related issue. Gapping? Given the readings for RH in your basement this would tend to suggest the flooring may not have been acclimated to the room it was installed in. One of your comments suggest the flooring was stacked in this unheated basement. I would suggest perhaps running a dehumidifier year round in the basement to keep the RH between 40-45%. I doubt using a water borne coating had anything to do with any of this. While they are called water borne, there really is only a minute amount of water in modern coatings of this nature.

It doesn’t matter that the floors are tongue and groove regarding board replacement. Make 2 saw cuts down the center of the cracked planks and remove that center piece of plank between the cuts. Then remove the lengths on each side with hammer and chisel. Remove the bottom edge on the groove side of the new plank, apply glue and tap the new plank in place with the tongue being the leading edge. That isn’t all that difficult really.

You could see if you have an inspector from the National Wood Flooring Association who would be willing to come and give a report.

I understand not wanting to go to court. That drags it out, doesn’t fix the problem and just causes everyone a lot of pain.

Large slivers of wood have broken off leaving big gaps

Q: We purchased a foreclosed home and it had water damage on the hardwood floors. We have been here 5 years and within that time large wood slivers have broken off leaving big gaps. We were told that nothing could really be done because of the heat expanding it, that it will continue to get worse. Before we go ahead and tile I would like to try and save these floors. I love hardwoods, but can’t afford to put in all new flooring.

A: I suspect the edges are breaking because the floor has been sanded too many times and the stress of the water damage (which does swell the wood) was just too much for the floor. If there is a lot of flex between the oak and the sub floor that would put even more pressure on these thin edges when you walk over those areas. It depends how many areas have splintered as to weather it is worth trying to keep. I have used a polyurethane adhesive in such gaps. It does hold the 2 boards quite well, but expands as it cures. So you would be wise to tape the floor along and around the gap first. This adhesive is in bottles from Home Depot. It’s not the thick adhesive in cartridges. This is moisture cure polyurethane adhesive. Also, you will have to cut the excess away flush to the floor with a sharp knife when dry and spread some wood filler over top of it to try to colour it and fill the air pockets it has a tendency to leave.

Repairing a split/crack in one of the boards

Q: We just recently bought a new house that has hardwoods throughout. In one of our rooms we noticed a split/crack in one of the boards. Can we replace that piece or repair it in some way? It seems like it could get worse, like someone could catch their socks on it. Any suggestions?

A: Of course, a piece can be dropped in after cutting the old piece out. You will need a matching board, a circular saw, hammer, chisel and some adhesive.

Similar Q: I recently installed hardwood flooring in my living room. One of the boards has a crack in it. It was not there when I installed it. What would cause this? Is there a way to repair it?

A: It was there when you installed it. You just didn’t see it. Now, with shifting of moisture levels it has opened up a bit. Replace the board.

Best product to fill gaps

Q: What is the best product to fill gaps in a hardwood floor? What is best wood filler for hardwood floors? Or putty? I am refinishing.

A: There are a lot of different fillers on the market. I haven’t used them all. Woodwise is OK, but like most of them will crack out if there is movement between boards. The toughest one I’ve ever used is Timbermate but it is quite expensive and difficult to work with. For small, occasional gaps and nail holes I like a tube filler called Color-Rite. It comes in hundreds of tones and is easy to work with and being more of a caulking won’t pop out. There are also stain-able adhesives on the market that have a place.

Related Q: I have old, wide plank chestnut flooring in my kitchen/dining area. The boards are approx. 12′ wide and 1 1/4′ thick. The house was built in 1803. I am looking into what I need to do to prep and refinish (seal) the boards. They have not been addressed in approx. 10 yrs. They are not smooth and there are spaces between ranging from 3/8 to 1/2′. Is there a caulk of some sort that I can fill the gaps with?

A: Wow. I’d love to see that floor! You might take a look at Timbermate:

Related Q: Our old wooden floor has some very small openings (i.e. small pieces missing). What do you recommend we use to fill these small openings?

A: Any colour matched wood filler such as Color-Rite would do the trick (comes in a tube) or any wood filler which can accept stain if you need to match a particular colour. Any wood flooring retailer will carry such products.

What causes cracking in wood boards

Q: What would cause cracking in wood floors, board ends and the centre of the boards 6 months after installation?

A: What species of wood is it? Some very hard exotics seem prone to splitting. Likewise, sometimes a piece of oak can have a crack in it but not be noticed during installation; it can appear later as the floor shifts with humidity change.

A couple cracks and scratches on newly installed floor

Q: I have recently installed hardwood flooring. I have noticed that, on some strips of wood there are scratches and in 2 strips of hardwood there is a crack about 3 inches long. Please advice as to how I could fix this, how to repair cracked floor boards. The hardwood used in this case is cherry kempas.

A: You will have to replace the cracked board, and probably the scratched ones also. You could try hand sanding the scratched boards and applying a water borne coating to the entire strip in the appropriate sheen but I don’t think you will get a match.

Filler that won’t crack?

Q: I was wondering if you could help me with a flooring wood filler cracking / polyurethane issue. My floor was professionally refinished 1 year ago and was to have a ‘worn’ look to it. We left many gaps and wanted only to fill the gaping holes and to make the entire house seem uniform in its’ ‘old world’ floor appearance.

One year later, however, the filler has separated in several areas, causing an open space for debris and dirt to land. The floor had 2 coats of Poly, but these gaps do not appear to have any poly stopping dirt from entering into the cracks.

My question: The floors still look great and we like them to look old and worn, but we wonder if these gaps are going to soon cause problems or if this is a refinishing issue that should not have appeared so soon. Is there something we need to do, like apply more poly, or is this just typical wear for wood flooring?

A: The only wood filler (I know of) which makes boasts about not cracking out is Timbermate. As robust as this product is, it also can separate if there is shrinkage of the floor, which is what it sounds like has happened to your floors. This has nothing to do with the sanding-finishing job that was done. You might want to buy a colour match tube of Color-rite filler/caulking to try. Polyurethane is not a gap filler.

How do you fills gaps in laminate floor?

Q: How do you fills gaps in laminate floor? There are gaps between the boards in my laminated floors.

A: There really should not be any gaps between laminate if it is a decent product to begin with. There are all sorts of wood filler on the market to choose from. It probably won’t look great. But you can fill gaps in laminate flooring with them. If there are not many gaps, consider a tube filler product such as Color Rite.

Filling gaps in pine floors and planks

Q: We have pine plank floors in our century home and they all seem to have developed gaps up to 1/4′. What do you suggest to filling gaps in pine floors, so all the misc. floor things (dust, etc.) don’t buildup?

A: You might consider a product such as this:
You no doubt will have to tint it to get it to a close enough colour to match the pine floors.

Similar Q: Is there a product that will fill gaps between the long planks for a polyurethane covered floor, that can be applied to a large area? Using wax sticks seems like it could take days to apply. I’m wondering if a colored paste wax might do the trick? Any help appreciated.

A: You could apply a product such as from Final Touch with a putty knife or trowel. You would have to wipe off the residue from the finish before it dries with a damp cloth, and you would have to apply stain or finish to the gaps after it dries.

Gaps developing between some boards

Q: I have hardwood installed throughout my home (maple 3 inch). Lately, I noticed some gaps between some boards. Maybe 1/8 inch or less. I have air exchanger installed. What could be the cause of these gaps? Our home is 1-1/2 years old.

A: The humidity levels are too low. Common problem in winter. In cold climates I would try to keep the RH in the home near 40% RH.

Similar Q: Unfinished oak flooring was installed in our home a few years ago. Sanded and finished on site. It now shows cracks at the end of boards (not down the side). Is this from a lack of humidity?

A: Difficult to say, because wood flooring usually expands and contracts side to side, across the width of the floor. Though in the case of quarter sawn, it expands and contracts up and down. Shrinkage and hence gapping does indicate a lower moisture content in the wood compared to when it was first installed. If the shrinkage is more severe the top coat finish may stretch and fracture making the gap more obvious.

What is “checking”?

Q: I hear our new engineered hardwood floors are ‘checking’ everywhere. Though I’m not sure what checking is — please describe and is this normal?

A: I wouldn’t have expected an engineered floor to do this. Has a glossary of terms under their FAQ section which explains what ‘checking’ is. What species of wood is this? Another related site mentions some exotic species and the need to make sure the wood if properly dried or checking could occur:

Further, I have a wood dictionary which defines ‘checking’ this way: a lumber defect caused by uneven shrinking of the wood during drying. A checked board has splits which develop lengthwise across the growth rings.

Is it possible that this product was purchased from some far off place such as…let me see….China? Did the installers take moisture readings of the product before they started installing? If it had abnormal readings for whatever reason and then started drying out after installation perhaps this may have caused the problem. However, in that severe scenario, I would also have expected separation between the boards themselves. I think the manufacturer should send a representative to have a look.