Spots where I used oxalic acid (wood brightener) are lighter after finishing

Q: I have just completed refinishing a 55 year old white oak floor. To remove some water spots I used oxalic acid (wood brightener). It looked great when the wood was raw, however, the water based urethane made these areas appear lighter and bleached out in appearance.

How can I have these area blend into the surrounding floor boards?

A: I think you might have to accept it and live with it. What are the options? Sand it all down again and either bleach the entire floor or stain it. How thick is the wood? It may be too thin to take this amount of sanding.

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.

My hardwood is in a convex shape (cupping vs crowing)

Q: My hardwood is in a convex shape; meaning, the two sides of the wood are up, but the middle part is down. A “C” shape. What is going on and how can I fix it?

A: This is called “cupping”. When the centre is raised it is called “crowning”.

Both are caused by excess moisture in the wood. It can be caused by extremely high humidity, dampness under the floor in a crawl space or a water leak from somewhere in or about the house. It could be from the roof or a window with large amounts of water seeping inside the wall and under the floor. Or could be from a leaking dishwasher, bathtub etc.

Find the source of moisture and eliminate it. A dehumidifier may help. When the moisture in the flooring is within normal range (you need a moisture meter) and it hasn’t flattened out on it’s own, it would have to be sanded flat.

Related Q: Our sink clogged and our dishwasher had leakage in the kitchen, which has tile flooring. On the other side, in the living room, our hardwood floor started cupping – the next day. Even though we had cleaned up all the water. Does cupping happen this soon after water leakage or could it be from previous flooding?

A: Water has likely gotten under the floor. Cupping occurs when the bottom side of the wood is wet and the edges curl upward. Crowning, when the center of the board raises is from excess water on the surface. This seems clear. The dishwasher leaked and the water ran onto and under your wood floor. Unless it actually heaves I would let it fully dry out and see what it does. You can’t do a thing with it until then unless you intend to replace the floor, in which case removing it as soon as possible will help the drying of the sub floor along.

70% of our floor, installed over concrete, is cupping

Q: I had a very expensive hardwood floor installed on concrete about a year ago. It started cupping in places within a month, and now the problem has spread to about 70% of the floor. I have had both the manufacturer as well as the company who installed the floor originally back to inspect the problem. Nobody can give me a satisfactory reason why they should not replace the floor. Can you suggest a reason why “it just happened” and they should not be expected to fix the issue?

Is there a product they should have used to seal the floor, if in fact “the concrete is bleeding moisture”? Should they have tested the moisture level of the concrete to check for the need of said products use? This is not a fly by night business, so I trusted my purchase would be installed correctly and the manufacturer would honor a warranty for a faulty product. Please if you have any information or suggestions, I would appreciate any help!

A: If this floor is below grade there probably isn’t a solid wood manufacturer who would warranty it.

In any case, if installing on concrete even a slab at ground level the slab should have been checked first for moisture penetration. If I faced such a floor “bleeding moisture” I’m not installing the floor directly on the concrete. Clearly you have a moisture issue.

There are a number of adhesive type spreads available which serve the purpose of both a sound retardant and moisture barrier. Bostik makes such a product.

In your case it sounds like you may have been much safer putting down some type of membrane over the concrete then using dry core, for example, and installing an engineered floor on top of that.

If you have moisture coming through the concrete it is only a matter of time before mold also becomes an issue.

Crawl space or leak in kitchen to blame for cupping?

Q: I have a problem with my red oak hardwood floor cupping. It started slowly at the island in the kitchen and has spread slowly. The floor is less than 4 months old.

With background: I had a hardwood floor installed in a foreclosed home that I bought. The home initially had water damage and hence we had to remove the entire subfloor and install new boards, then tar paper (felt paper) was laid, and then the hardwood was laid. The hardwood sat in the home for over a week before installation. The man that installed the floor has done this type of flooring for about 20 years.

The house is over a crawl space that does have some moisture issues. There is proper ventilation, but we have not gotten to laying a tarp on the dirt. I just recently notice a leak under the kitchen sink due to an improper installation by a plumber. I am not sure where to place the blame.

I would like to know if moisture can get from a crawl space, through the tar paper, to the floor and cause the damage, or if it would be more likely the plumbing that has caused the problem? Also, is it possible the floor could return normal? We live in Michigan.

A: Cupping indicates excessive moisture moving from the bottom of the floor to the top. Of course a wet crawl space is something you want to attend to. The felt which was installed first serves as a moisture retardant. I wouldn’t view it as a vapour barrier since it has dozens of holes punched through it when nailing down the floor. Laying out a tarp on the dirt should help. However, the leak at the island sounds like the most likely source of the problem.

I have seen floors flatten out in time. You will need to be patient and give it that time to thoroughly stabilize and see what it does.

Sanding a floor before this moisture stabilization occurs would likely lead to the floor crowning, which is reverse cupping.

Will ridges flatten if we place weight on them and ventilate?

Q: We installed prefinished hardwood in a bedroom 1 1/2 years ago. The tenants ducted the dryer exhaust from the laundry across the subfloor and joists below, and never checked the vent, which became plugged with lint. We now have a section of floor which the 3/4 inch thick X 2.75 inch wide boards have swollen and bulged upwards, forming ridges.

Will these ridges settle if we place weight upon them and ventilate the area below? We have spare replacement lengths to repair the whole area, but prefer to delay that if possible.

A: Ventilating is a good idea. I have seen such floors flatten. Give it a month or 2 and see if it does.

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.

Water damage to my solid hardwood floors when a pipe broke

Q: I had water damage to my solid hardwood floors when a pipe broke. My floors are parquet and probably 50 years old. They buckled. I brought in a dehumidifier and the floor actually dried out and is now flat down. Now, they are still cupped and there are some gaps in the floor.

I can’t decide if I need to replace the floor or if the damage could be fixed by refinishing. I’d appreciate your thoughts. Thanks!

A: The structural stability of the floor has likely been compromised. A water soluble adhesive was likely used when installed. When the flood occurred the adhesive softened and the floor buckled. It has gone flat since, but how well has it bonded to the adhesive? I would suspect the entire floor or large parts of it are now or will become loose.

I would probably consider the floor lost. Somebody is going to have to sand it to get it really flat again and all these pieces/slats are going to start popping loose.

Follow-up Q: Thanks for your reply! The floor was put down in the 1950’s using a black, tar like adhesive. The adhesive appears to have come loose in the part of the floor most affected.

The problem is, only about 20% of the floor was affected and the rest is still in pretty good shape. They don’t make the floor anymore so I guess I am looking at total replacement. I hate the thought of all that good wood going in the landfill!

A: Is this parquet block? Tongue and groove, possibly 3/4 thick? Have your floor guy put his moisture meter on the floor. If it is stable, it can be sanded over. If these are blocks and some are damaged you may be able to make your own from 2 1/4 wide strip.

Related Q: I have tongue and groove, soft pine flooring. I had a water leak on a section of the floor. The floor did get wet, and after using the shop vac to get the water up the floor starting drying and started producing a cracking sound. Now several of the floor boards have risen up along were they come together. What can I do to repair them, short of replacing them?

A: I would leave it for a month and see if it drops back down on it’s own. If not, it will have to be sanded flat.

Sanding marks in spot patch

Q: I have waxed parquet oak floors. There are several places where the stain was lightly sanded out, and then stained to match the surrounding wood and waxed. However, the sanding marks still show.

A: It sounds like the spots were sanded across the grain. You need to sand with the grain so these sanding marks don’t show.

Floors sticky after being treated with insect killer solution

Q: I had worms in my old hardwood flooring. They were treated with some kind of insect killer solution, and after 2 weeks the floor became sticky. Should I sand it down and stain it or is there an easy solution to my sticky floor problem?

A: I think I would be asking the person or company who treated your floor how to neutralize and remove the residue. And I don’t think I would be handling it, walking on it, letting children or pets near it until this is resolved. It might be as simple as wiping it down with a wet cloth but check first and don’t be applying any other type of chemical until you know what the outcome might be.

Cold causing wood floor to buckle?

Q: My hardwood floors have buckled in my 1928 mountain home, due to the heater being destroyed in the basement which flooded. How can I fix them?

A: So, from your description it sounds as if the moisture is rising up from the basement, going through the sub floor, the hardwood and out. I would get dehumidifiers running, one in the basement and one on the main level and then wait it out and see if the floor will flatten back down.

Follow-up Q: The basement has been dried out for a year. I haven’t replaced the Heat A.C. unit. It’s the COLD that’s making them buckle. I don’t know how to get them to flatten out again.

A: I don’t think it is the cold that is causing your floors to buckle. Only moisture in excess can do that. I would buy a couple of hygrometers that show temperature and relative humidity. Place one in the basement and one where the floor is buckling. If you could get your hands on a moisture meter you could also test the sub floor from the basement and the floors upstairs to see what type of reading you get.

When you have a better idea what type of moisture levels you are dealing with you can decide if a dehumidifier or 2 may help. I think if you can get the floors down to acceptable limits it may flatten on it’s own. It might also help if you can remove the quarter round on the side walls to see if the floor is installed tight against the baseboard or outer walls. If it is, the floor has no room to expand. If you could cut 1/2″ off which would be hidden under the trim anyway, that would help relieve the pressure.

Related Q: This house is less than a year old. At first when my partner and I moved into this new house everything seem to be fine. A couple months later, we noticed that the hallway timber floor was starting to lift. Eventually the floor lifted quite high and some parts of the timber are starting to split. Any idea what would cause this problem?

A: There is definitely a moisture issue at play here, whether it be a leak from the bathroom or laundry room. The floor is buckling because the boards are growing due to increased moisture content. It will take some investigative work to isolate exactly where the excess moisture or water is coming from.

Similar Q: I am in a condo and the tenant above had a flood a year ago. A team came into my condo to see if there was moisture under these very expensive wood floors, and there was. Some kind of air sampling was done. They brought in 2 fans and had them going 36 hours (there was no water to “see”). Now, more than a year later, the floors are buckling. Just where they had put the fans. If I replace only some of the floor it will look goofy. Also, since so much time has lapsed do you think the upstairs tenant’s insurance will cover it?

A: I honestly don’t know but it is worth a try, as it seems apparent the problem with your floor is connected to the water from your upstairs neighbour. Do you have some type of report from when the people came in to check for moisture, affirming that their was some?

Black stains where some of the nails were

Q: I removed the carpet from our stairs. Some nails from the carpet strips must have been wet a time or two, because there are black stains where some of the nails were. It looks like rust to me. How can I remove these stains? Or at least lighten them? I thought that Clorox may work, but some say that this will darken the stain.

The Fe will react with the Cl and form FeCl3. CLR (The household cleaner) does not recommend any use with wood. I looked at OxiClean and there was no information there. CARBONA has a product that is targeted for rust, but it is only available over the Internet. Any suggestions? What about something as simple as vinegar or baking soda?

A: Household bleach isn’t near strong enough to remove stains in wood. Try to scrape or sand them out. The treads will have to be completely sanded and finished.

Similar Q: I am redoing my oak hardwood floors and there are black marks from staples used to staple down the carpet pad. How do I get rid of these black marks?

A: If they won’t sand out and you feel they are too much of an eye sore, you could use a fine nail set and depress them below the surface, then fill the depression with a wood filler that will be less visible.

Grooves from piano being moved

Q: We recently sold our piano. We neglected to tell the people moving it out that they should lay something down to protect our hardwood floor. We now have grooves going all the way from the living room through the dining room from the piano wheels. We are renting the property, which makes me really nervous! When I run my fingers over the grooves, it seems as though they are only in the finish of the floor rather than the wood itself. (I’m guessing that’s a good thing?) What is the best way to fix this, since they continue through several rooms? Does the whole area have to be stripped and refinished?

A: If the depressions are into the floor surface which is likely you will probably have to sand the floors. You might try wetting a towel, placing it over a spot in an inconspicuous spot and iron it dry. See if the moisture is able to get past the finish and pop the wood back up. It’s worth a try.

Matching sheen on spot repair of heavy traffic area

Q: I would say 90% of my 1956 oak wood floor is pristine, but the area of heavy traffic flow has basically no finish remaining. I didn’t do anything to fix it and then the real problem came when my cat became ill and threw up in several places in this area. It bleached the wood, which I attribute to having no top coat left, because when he threw up elsewhere it did not bleach the wood. I weighed my options and honestly would rather travel than pay a couple thousand to refinish a floor, so I decided to try to at least improve the look. I live in a sort of low rent neighborhood so am not overly concerned about resale, which gives me some freedom to experiment. I prepared the area, sanded, used a conditioner, stained, and now put a coat of satin poly and lightly hand sand with 220 grit. Problem is the satin poly is a bit too shiny for the rest of the floor. Is there anything I can do at this point? Mainly, can I change the type of poly for the second coat to a lower luster sheen? It already looks much better.

A: Given the age of the floor it is possible that it actually is a wax finish which could help explain why the satin poly has more of a shine than the old finish. Another possible explanation is that you didn’t stir the satin well enough. Having said that I see 2 options for you.

There are matte and super matte finishes available which have no shine whatsoever. You could coat with that type of coating or use 3 or 4 zero steel wool or super fine sandpaper in the range of 1000 grit or finer to buff the satin coating until there is absolutely no shine at all.

Newly installed oak wood floor is cupping

Q: We had 1/2 white oak installed in our dining and kitchen area to match the 40 year old oak floors. The contractor did not acclimate the new wood at our site. It is now cupping, but the old floors are not. Do you feel like he should replace the flooring?

A: I think you need to determine why the floors are cupping, which is a clear indicator that the moisture in the wood has risen sharply since being installed in your house. Why would that be? Do you have a leak some place? Is this over a crawl space that is very wet? It couldn’t be so humid in your home at this time of year. Some measurements need to be taken to find out where all the moisture is coming from.

Similar Q: We had new oak floors installed in summer 2016. After about 7-10 days we noticed planks lifting in one area. After about 4 weeks it was up to 15 planks lifting. In addition, the entire floor is cupping. The installer believes it is all due to too much moisture in house. However, the new hardwood floor replaced an old hardwood floor. Never had any issues with the old wood floor. In addition, the other rooms in the house on same floor with new hardwood floor are also hardwood, we’ve never had any cupping issue. I think it is a installation problem. What do you think?

A: If the floor is heaving and cupping this is a sure indicator of a moisture imbalance. It sounds like the floor is under pressure. Somebody should come in and check with a moisture meter. 7-9% is normal. Any reading significantly above this will create a problem.

Follow-up Q: Thanks. We tested moisture in different parts of the floor. Again every plank appears to be cupped. The floor is about 700 sq feet. The monitor reads moisture levels all over the map. Anywhere from bone dry to 15%. I asked that the manufacture of the floor be called in to inspect. Anything else I can do?

A: It is always a good idea for the sub floor and floor to be installed are tested with a meter for moisture content. The sub floor should not be more than 4% higher than the floor to be installed. I don’t know if this was done. I don’t know how high the humidity is in the house. But generally cupping where the edges of the boards are curled as opposed to crowning where the center of the board is raised is from the moisture coming from the underside of the floor. This isn’t a new house is it?

Follow-up Q: Not a new house.

There are rooms (den and office) under the floor with new hardwood floors. We have custom wood furniture in that first floor room and custom wood crown molding. Both are about 5 years old. No warping or sign of moisture problem. The new hard wood floors replace older hardwood floors. Older floors were perfectly straight even in summer months.

A: It is bewildering because if the new flooring was poorly stored and not protected before delivery to your house and it had unbalanced moisture content it likely would have shrunk and produced gaps after being installed in your place. I would have the manufacturer send a rep and perhaps if you can contact an inspector from the National Wood Flooring Association they can find the problem.

Indentations from a floor nailer?

Q: We had a new hardwood floor installed three weeks ago. When we got to installing the baseboards we noticed hundreds of indentations. Could they be caused from a floor nailer? We haven’t used the room so it isn’t us that did it. How could these indentations occur? We checked an open box of wood left over and there were no scratches on these. They are everywhere, some the whole length of the board.

A: Could be from a floor nailer, unless they are round dents appearing even in the center of the boards, in which case it may be high heel dents.

Rough spots from vinyl adhesive

Q: When I bought my home 7 years ago there were vinyl stick tiles on a 3×3 area in front of the door. I removed these tiles years ago. I’ve done all the steps required to refinish the wood floor. I used 50 80 and 120 grit to prep the floor. I’ve stained the floor. Now that I am applying the poly, I notice rough spots where the adhesive was on the floor. How do I remedy these spots?

A: Did you fully remove the adhesive to clean, smooth wood? You should be applying 3 coats of finish at any rate after sanding with fine sand paper between coats. Hopefully this will result in a smooth floor. I think you were fortunate to be able to rough off the mess with 50 grit.

Follow-up Q: Thank you for your response. I went ahead and spot sanded the areas with 120 and my orbital palm sander. It seems to have worked so far. I just reapplied a coat of sealer and so far so good. When I originally removed the tiles years ago I used an adhesive remover and didn’t even see the affected areas until I applied the first coat of sealer. There were other areas along the same wall where there was still adhesive on the floor when I sanded yesterday and those spots are not visible. I’m wondering if the chemical I originally used to remove the glue damaged the wood to an extent that I had to sand deeper in those spots.. guess I’ll see when this coat dries.

A: You would think and hope after years of exposure the chemical you used would have neutralised by now, but you never know. As long as you have adhesion with the first coat, you should be okay from here on. Just make sure to thoroughly abrade the finish and clean well before applying another coat. Are you using water borne or solvent/oil based finish. If it is water borne you should be able to apply succeeding coats without buffing if applied within a specified number of hours, but check the documentation or label before doing that. Oil based should always be sanded first to completely scuff up the coating.

Follow-up: It’s a water based coating. The directions say 2 hours between coats. I did my dining room floor several months ago and had great success. It’s this one area that is troublesome. After sanding again and coating, some of the spots are gone but some came back. Definitely a learning experience. Thanks again for your input.