Boards are hollow, not glued down properly

Q: I built a new home last July. We have had ongoing problems with our engineered hardwood floor. Two certified inspectors state that the floor was installed improperly. 3100 sq. ft. Every single room has boards that are hollow, not glued down properly. Will these eventually pop since they aren’t glued properly? The builder says he sees no problem. Sure.. he didn’t pay for the floors!

A: I think it would depend in part on how many of these boards with no adhesion exist and especially so if there are several together in a group. I believe Bostik has an adhesive you can inject into the floor. A tiny hole is drilled through which an expanding adhesive is applied by a tiny tube. This would take care of any random boards that are hollow beneath. If you are talking dozens of them, that is another story.

Wax to stop the creaking sound?

Q: What can I do to stop the creaking sound my wooden floor makes when you step on it? I heard that you should wax the floor.

A: You shouldn’t wax a floor if it is finished with a polyurethane or similar top coat. Waxing won’t stop the creaking in any case.

The movement in the floor is very likely also related to a loose and moving sub floor. The only sure way to remedy this is to replace the floor. Nail down the old subfloor with spiral nails and if need be, screw at least 3/8 spruce sheeting over top, then a new hardwood floor.

Related Q: We installed hardwood floors in our house 2 years ago. We used all short boards. It looks great, but the whole floor pops as we walk across it. I thought that maybe it was because we have so many joints, having used the short boards, but we have no idea how to fix it.

We put a new layer of OSB down since taking out the old floor left the original subfloor weak. Do you have any suggestions on how to fix the popping?

A: If the problem is the OSB no holding the nails, there isn’t much you can do short of removing the floor, installing plywood and then installing the floor again. Perhaps you can fire the occasional 2″ nail from a trim gun and putty the hole, but I’m not very hopeful that will work.

Hickory floor making popping sounds

Q: Our home is 70+ yrs old with original pecan/hickory wood floors. A week ago we had a floor restoration repair company repair and replace a badly rotted area caused by an adjoining bathroom leak many years ago. After cutting a 3′ x 5′ area of flooring and opening they found it rotted through the floor joist and someone previously cut a support beam which was just hanging.

They had to cut the rotted joist out and married a new joist in after supplying a new section of support beam.

They then sealed the hole, installed moisture barrier, new sub-floor, new wood floor boards, stained to match existing, sanded the rest of the floor, restained, sealed all with water base products. The floor is beautiful and you cannot tell anything was done. But for last 3 or 4 days we have heard loud popping from the room, which is empty right now.

Should we be concerned?

A: No, I don’t believe there is anything to worry about. Hickory is rather sensitive to environmental changes and other disturbances which means it expands and contracts a lot. I hope the guys used a sealer under their coating which has some stretch to it. I would keep an eye on that. What along board edges for any signs of cracking. As an example of how most things move, I have a steel roof. You should here the noise it makes on the coldest winter nights. It bangs! Your popping sounds should stop once the floor settles down.

Follow-up: Thank you SOOOOO much! We will keep eye on edges as you said.

Lots of loose boards in engineered wood floor

Q: What happens to an engineered wood floor when a home is left unoccupied with no power/AC for a year? I’m about to buy a repo with lots of loose boards. Is this the reason why? Too dry and shrinking away from the floor glue? I know they used glue originally via the exposed edge at dishwasher area.

A: I don’t think that is the reason. If it is a repo, the owner may have been short on money and this was a DIY project. He may not have used the correct trowel to sped the adhesive (too small a notch) and probably didn’t roll the floor so he got inadequate grip on the back of the boards with the adhesive. That is my theory.

Follow-up Q: Is there any solution short of replacing the boards? I may be able to remove and re-glue some areas that are totally hollow sounding but there are places that have pockets that are loose. How do I fix these?

A: Bostik makes an injectible adhesive. Drill a small hole and inject. The adhesive will expand and fill the void below the floor, gripping both the sub floor and finished floor.

Cracking noises when we walk on engineered wood floors

Q: I had engineered wood floors installed almost 2 years ago. The floor continues to make cracking noises when we walk on it.

What is causing the cracking sounds and is it due to faulty installation?

Also, the installer used silicone caulking to glue the bottom of the baseboards to the wood floors, is that normal?

A: It sounds like the surface the floor was installed on may not be totally flat, so when you walk on the floor it moves up and down causing a rubbing between boards or panels. I doubt he was attempting to glue the base to the floor.

Again if the sub floor was not flat, there would be spaces under parts of the base. He may have used caulking to fill that in. Also, if he felt a draft coming under the base, that would be another reason for the caulking.

Related, not the subfloor Q: Since the day they were installed about six months ago, our hardwood floors ‘crackle’ when we walk on them. (It is definitely the boards themselves, and not the subfloor squeaking.) It occurs all over: in the living room, hallway, etc.

This is a second floor installation. The first floor is fully finished and heated. Living room humidity ranges from about 35 to 55%. Our contractor says floor is not perfectly level, but he’s seen worse (and never had this degree of crackling.) Suggestions?

A: I would let the floor go through a couple of seasonal cycles. I installed one floor that had such a tight fit on the tongue and groove, it was difficult to work with. For a number of months it wold make cracking sounds all on it’s own. No doubt, this was from slight movement as the floor reacted to humidity conditions in the home. It adjusted in time.

Popping sound in hallway one year after install

Q: We live in a condo on the 10th floor. We put in engineered Brazilian hardwood. It’s been one year to the date. Now in one small section (hallway), when you step in a few spots there’s a popping sound. Sometimes it is very loud. What causes this and what will fix it?

A: It sounds like some expansion has occurred. Is it possible there is a leak someplace? You could have someone come in with a meter and check for moisture levels. You may simply have to buy a hygrometer (from an electronics store) and monitor the indoor relative humidity. You didn’t say if the floor was glued down or is floating. If it is a glue down, you may need to buy some adhesive that is injected through a tiny hole in the floor. this will expand and fill any dip in the concrete beneath if that is a problem. I believe Bostik makes such a product.

Is there a way to fill in dips?

Q: I put down some 3/8 engineered flooring on a slab with glue. In the rush to get the job done within the time I had allowed, apparently two small dips in the slab were missed. Now there are two areas, about 10 square inches, where the floor is just floating over the glue. If you step on the area, the floor dips, adheres to the glue for a moment, and then pops back up. Is there a way to fill in underneath these small areas to stop this problem, without pulling up a lot of floor to get to the spot?

A: There are indictable adhesives on the market. You drill a tiny pilot hole, insert tube nozzle and squeeze. The adhesive will expand under the floor and fill the cavity. I believe Bostik makes just such an adhesive.

Related Q: My dad and husband recently installed an engineered walnut floor in my kitchen. They ended up with a low spot, due to an uneven sub floor, resulting in the occurrence of a “popping” sound when you walk across the uneven area.

This, unfortunately, is a high traffic area. What is the best way to correct this problem?

A: If they had put a nail in the tongue at that spot it likely would have pulled the board down and helped prevent the sound. But, stuff like that happens.

How about this: there are injectable adhesives you can use which can be squeezed through a tiny hole drilled through the board and the adhesive will expand into the space under the boards. If you have access from the basement, you could even do this through the sub floor. That is one idea. You might find that this annoying movement will come and go.

Glued down floor is popping and creaking

Q: Doing a remodel about 18 months ago, we installed bamboo flooring over concrete. Going with the advice of our contractor, we painted the floor with Kilz Primer then glued the bamboo directly to the concrete. We placed weight on the floor and let it dry overnight. Now it is popping and creaking in the areas that are most often walked on. Is there any way we can fix this problem short of pulling up the floor and replacing it? Thanks for any suggestions.

A: I’m wondering if the adhesive has not bonded to the primer. What does the manufacturer say about using their adhesive over paints and primers?

Related Q: The guy doing my home improvement installed Schon 3/8″ x 3.5″ Brazilian Cherry engineered wood on my bathroom vanity floor. He installed it directly to the concrete with some type of silicone glue gun (the style for caulking). Is this a good or recommended method? The bathroom sounds a bit clicky and spongy in places. Is silicon any good for this? I live in So California.

A: I’ve never heard of anyone taking this approach. I would have suggested Bostik’s Best or some other polyurethane adhesive. You might want to look up the product online and see what their recommendations for adhesive would be.

Popping and footstep noises

Q: My house makes noises. It’s coming from the upstairs area between the kitchen and the first room. The entire upstairs is wood floors. It makes 2 distinct noises, a stomp and a pop. Is it possible the noise is coming from the wooden floor? Because sometimes after the stomp a sound like footsteps occurs. I’m an Islander and live in Seattle,WA and my family believes that the dead are trying to communicate. Please help. It’s driving me nuts. Thanks.

A: I don’t know how old the house is or what the dimensions of the floor are nor what sub floor it is sitting on. It could be possible part of the sub floor is loose and that spot will make a noise. It might be good to check the relative humidity in the home and also the floor itself with a moisture meter to determine if there is excessive expansion in your floor.

Related Q: Twice there has been a loud pop noise in my house, any idea what it is?

A: Possibly expanding hardwood floors. Any moisture or humidity issues? Everything expands and contracts. Even steel roofing. It can make quite a bang.

Floors popping after nearly 5 years

Q: My Shaw engineered floors have been down 4.5 years, and one area recently started to pop when walked on. It spread to 4 boards. Then there are two pops under my oriental rug. Then one board in the bathroom started, and finally an area of 3 or 4 boards in a hall. The floor guy is mad at me because this happened! Why, you might ask, as I ask? Apparently he doesn’t know what to do. The floor under the pops feels spongy when walked on. The floor is on concrete, glued down. Having not been educated on laying floors of any kind, I’m at a loss also.

I read a lot on your website, will that injectable glue work on these floors? An independant inspector came out and just said it was not the manufacturer’s fault. His report was so vanilla, that one could make it mean anything or nothing. The installer paid the 150, and he thinks it means that he is in the clear. Can I expect this to continue to happen in other spots? This occurred about 3 months ago, and I’m wanting to put my house up for sale, but wondering if no one will want it due to these 4 areas of popping wood. Can you help me? I live in upstate South Carolina. We did have heavy rains this past winter,but there is no smell of moisture in my house and I use no humidifier. The report said that the inside conditions were 55% RH and 70 degrees F. Moisture presence in the flooring measured with a Tramex moisture meter averaged 15.6% with 24 total checks made.

A: Clearly something has changed in the environment. It sounds like your floors have swelled and this side pressure is causing the floor to raise in these areas. 15.6% moisture content in the wood I consider high and not normal. Is it possible you have a slow, hidden leak someplace and moisture is creeping under the floor? The moisture level in your floors will need to be corrected before you can think of going to other measures such as injectable adhesive. Did the inspector think this reading was fine?

Follow-up Q: Thank you so much for answering. Do you mean a leak in a water pipe under the floor? What do I do to find out? The areas where the popping occurs are far apart. Each place involves 1-3 planks. There are 4 places, rooms apart. The inspector was not useful in my opinion. He was working for the guy who laid the floor, so it seemed to me he thought it was the installer’s lack of preparing the floor, but didn’t have the courage to say so. He kept speaking about how an installer had to prepare cement because it was never even, but put nothing of the sort in his report. What do you think should be my next move? I want to sell in a few months, and need to have everything in good condition. Thank you again. There is no change in the appearance.

A: I would contact The National Wood Flooring Association and see if they have an inspector near enough that he would come out for an inspection. They will give you an impartial, honest appraisal. It could be that for some reason he didn’t get real good grab between the adhesive and floor. But why is this all happening now after 4 years? The spongy feel in those areas and the what I consider a high moisture level reading tells me to suspect something else.

I’d be interested to know the results if you are able to get one of the NWFA inspectors out to look.

Second follow-up: Good morning, I have consulted with my water provider, and there has been no change in the amount of my water usage, thus no indication of a water leak under my concrete. That’s a relief. Still eager to hear where you think I should start.

A: I don’t know what you should do at this point. As I mentioned in my last email, if you received it, the inspector who was there is NWFA certified. His report seems to indicate concern with the high moisture readings in some areas, 15.6%. He mentions in his report that some boards should be removed to check the concrete. I think you should phone him and discuss his report. He is certified. He has inspected the job site.

Third follow-up: Thank you, so much. I’ll let you know how things turn out, as you requested.

A: How old is this house?

Fourth follow-up: It is a 20 year old, middle unit of 3, one floor, brick condo. I have lived here 12 years. Previously it had carpet. The other owner spent more time at the beach than in the home, so it was not used much the first 8 years. No one in the units next to me have had problems with moisture. One still has carpet, and the other one has some type of laminate (Pergo?) that has been there the whole 20 years. The floor is still in excellent condition.

Only person in our neighborhood who had problems is one lady who had her Mohawk floor, mine is Shaw, installed just before I did, by the same company who did my floor. She has had the same problem. They cut into her floor and replaced the boards. I haven’t seen it, but she says it is bad looking. I will try to go by to see it soon. No one else in our neighborhood used the same company that we did. Both of us are widows. The other lady is older than I, and not very well. I think she just gave up. I haven’t asked her what they told her was the reason her boards were popping.

A: Interesting. I can only do so much. I’m far away. It seems odd your floor was down without any issues for several years and now you have these areas with high moisture content readings. I don’t see the point of changing the boards unless the cause is identified. How is the floor being cleaned? Is a lot of water being applied? Do you have a cleaning person helping you?

Last follow-ups: I use only Shaw hard surface cleaner which is what Shaw company told me to use when I contacted them soon after my floors were installed. Thank you again. Since I don’t really have any faith in my installer and it appears not to be his error? Where do I start to get to the bottom of the issue. Plumber, builder or who?

Thank you so much for your time. This has been very upsetting to me, and the installer has been so rude. He is so scared that it is his fault, that he would not help me get to the bottom of this. I definitely will do as you have suggested. In case I misunderstood the anything in the inspector’s report, I am including it in its entirety. After your response, I will begin my quest, and will definitely let you know what the final verdict is.

I appreciate your help very much.

A: Okay, this inspector is NWFA certified. He basically is concerned over the same issue I mentioned. High readings for moisture in certain areas which would require removal of some of the boards to expose the concrete and then test the concrete. My question is why it took this long for this issue to appear. Perhaps something has changed around the building? A drainage issue? I don’t know. The excessive moisture appears to be the immediate problem.

Old floor popping sounds during the night

Q: I know that the question of wood floors making popping sounds during the night has been asked; however my white oak floors are original to the house built in 1948. I did have the floors refinished about 6-7 months ago with water-based finish and like the others, the popping only happens at night without anyone walking on them. I’ve had this house for 17 years and it’s never done this before. Do you think it’s still humidity related? I live in Southern CA so it’s pretty dry here. Thanks!

A: As companies have been forced over the years to develop water borne coatings they soon discovered they also needed to develop special sealers to prevent an issue called side bonding. These coatings are more brittle and rigid than oil based finishes and thus don’t stretch as much with movement in the floor. I suspect the noises you hear are the finish stretching and cracking along the board edges or between boards where it slipped into tiny gaps between boards. Once that has completed the noises should stop.

Hollow spot in floating floor

Q: I wondered if you could suggest a fix please, for our new kitchen. The original floor was concrete, and this had levelling compound put on top, a floor fitters request. All looked okay, but there is a hollow spot in floating floor (now it’s all fitted where it creaks when you step on it, you can see the wood dip when you apply weight). Obviously it’s a little hollow in that area. The floor is floating engineered wood, sitting on a moisture barrier/underlay.

As the floor is not glued down, can I still inject adhesive though the board and wait for it to cure effectively “filling” the hollow rather than gluing it down? The hollow spot is only a few boards in, so I may do it from side rather than drill down. Or is there a better way? (The fitter is no longer with us, floor is a year old now..)

A: I think you’ve got the right idea for an easy fix. I believe Bostich has such an ‘injectable’ adhesive. I’ve never used it but I would think it expands as it cures, thus filling the void. So, if you can do this without drilling a hole, all the better.

Similar Q: Why are there air bubbles in the glue that I’m using for our bamboo floor? I recently installed my living room and now when you walk on it, you hear popping.

A: It’s possible that you didn’t get complete grab of the adhesive between the sub floor and the bamboo. This could be caused by something as simple as a slight depression in the sub floor. It’s probably best with a glue down floor to go over the floor with a weighted roller as you work. If there are hollow spots here and there you can use an adhesive syringe after drilling a tiny hole. This will expand in the cavity under the floor and stop the movement. I believe companies such as Bostik Findley make products like this.

Related Q: We just installed engineered maple over concrete slab. There are some areas of “hollow” sounds, when you knock on boards, but no sounds when walking on floor. What do you think causes the uneven “hollow” sounds?

A: A possible small dip in the concrete and perhaps poor grab of the adhesive in those areas. Was the floor rolled with a weighted roller when installed?

Floor popping after refinishing

Q: Oh my goodness….. We just had carpet ripped up and prefinished ash laced in to an existing prefinished ash floor. The installer then sanded everything down and restained. I went to look at it tonight and every single step I take makes a very loud “popping” creaking sound. It sounds like the fourth of July! Interestingly enough, everywhere the original floors were made no discernible sound. Only on the areas where the new floor was laid. I have not yet paid the installer. I sent him a message asking about it and so far no response. Is this due to a faulty installation? Is it something that goes away after the floor “settles”? I have a whole series of other work scheduled to be done before I move in which is only 10 days from now so I would rather not have to redo the floor, but I cannot live with the sound it is making. Thanks for your help,

A: It seems clear to me this should not be happening. Did he nail adequately? Did he make sure the sub floor was secured before beginning the installation? Did he acclimate the new floor before starting the installation? Did he make sure the ash was within 4% moisture content to the sub floor? So many questions. So few answers. It is easy enough to find out how far spaced out his nails, cleats or staples are. Get one of those magnetic stud finders and run it down the edge of the planks. Any time you pass over a nail it should point downward. You should find a nail at least every 10 inches or less.

Follow-up Q: Thanks for getting back to me.We questioned the installer and he claims that it is because he did three coats of water based sealer and there is so much moisture. We made him put in writing that the problem will go away as it dries but I am very sceptical! Does this sound like a reasonable explanation?

Thanks for all of your help!

A: I don’t know what product he used and I haven’t used water borne coatings in quite some time. However, I have used them off and on for probably 30 years. Having said that, from my experience it is really pushing it to try to apply 3 coats of a water borne finish in one day. And my bigger question is: why did he use 3 coats of sealer except that it is cheaper? And did he give you one coat of the finish which is generally tougher and is meant to stand up to wear? If that is what he has done you can expect this floor to need refinishing not too long down the line. Applying multiple coats in one day can cause some swelling of the wood.

Bamboo floor lifting in doorways

Q: We just had bamboo floors installed over cement, and now I’ve noticed the bamboo floor lifting in our doorways. Any idea what happened?

A: Do you mean it is buckling, heaving up or the edges of the boards are loose on a few boards? If it is buckling, heaving the culprit is likely a water leak somewhere. If it is the latter it could be the adhesive was missed in those spots or the floor, if it was rolled with a weighted roller missed those spots and failed to get good adhesion. There are injectable adhesives for situations like this or when there may be a low spot in the concrete. Bostik makes such an adhesive.

Similar Q: I just had click bamboo floors installed 2 weeks ago and now in nine certain areas they seem to be lifting off the subfloor, and popping when stepped on. What can be done to fix this problem permanently and cost effectively?

A: Perhaps there is a small dip in the floor (concrete?) under that area. If this is the case, though it would require taking the floor apart up to this area, it could be filled with layers of roofing felt to make the area flat. Seems like it could be a real pain though.

Pilot holes through the sub-floor to stop creaking

Q: Our 3 year old 3/4″ maple hardwoods (nailed down with a nailer) are creaking all over and some boards actually feel loose. It was nailed down to OSB on top of I-joists. I’ve checked the sub-floor (our basement is un-finished) and it is secure to the joists. I have tried adjusting the humidity and that didn’t help.

I was wondering if I could pilot holes through the sub-floor underneath and pull the hardwood down secure to stop the noise. Will this cause damage, because of the natural movement of the wood through the different seasons and the wood unable be able to move because of the screws? I just don’t want to make things worse, but it’s really annoying. How to fix a creaking subfloor?

A: Screwing from below is certainly worth a try. I would suggest drilling pilot holes using a depth gauge on your drill. I don’t like installing on OSB even though it apparently has been approved by the NWFA. This being a new build I’d even guess the builder went minimum code and only used 5/8 instead of ‘¾. Little wonder the floor is moving. There isn’t much really holding the cleat or staple and maple can be sensitive to humidity changes as it is.

New floor popping loudly in middle of night

Q: My question is related to your posting on “popping” or “cracking”, wood floor popping sound Q&A.

In my 2nd fl bedroom I recently replaced the old carpet to hardwood floor (not the pre-finished kind). We have, several times, been awoken by the loud popping sounds from the wood floor around 2-4 AM. What is the cause of that? Could it be the old sub-floor is very thin? When we walk on it, we don’t hear any noises. Thank you for your help.

A: My guess, especially since it is a newer floor is that it is moving slightly according to changes in humidity in the house. Especially when the fit of the tongue and groove are a tight fit noises like popping sounds could be heard. This should stop in time. Try to control the humidity levels in the house.

Similar Q: On the 2nd floor of my house I recently had the hardwood flooring replaced with new. Now when I walk in a room the entire floor crackles like breaking ice. If I walk around a few times it will stop for a while. At night I can hear it pop even though no one is walking on it. What is wrong and how can it be fixed?

A: Did the installers acclimate the flooring before installing? It sounds like there is some movement happening. If the milling of the tongue and grooves is particularly tight as the floor contracts it can make such noises. Try to control your humidity levels. I would think given some time the floor will settle down. Unless it starts to cup or buckle I would consider it a temporary annoyance.

Another Similar Q: We recently moved into a home and refinished the hardwood floors which had been down for 5 years. Spring has come (in Sydney) and the floors are now starting to pop and separate at some of the seams. Could this be caused by the refinishing?

A: It sounds to me that the wooden floors are simply reacting to changing environmental moisture levels in the home. Wood can and does release moisture that is in the air. If it is very dry the wood can shrink. Solvent based top coats generally allow more film stretch than water born urethanes. The popping may be the sound of the finish cracking at the joints from board movement. Perhaps you can add humidity to your home.

Squeaky floor without a sub floor

Q: My wife and I moved into a rehabbed 2nd floor condo this summer. It was built in 1970, has hardwood floors throughout, and tiles in the kitchen and bathrooms. As we’ve been living here, the wood floors (red oak, I think) have become really squeaky. A little Internet investigation lead me to think that most people with this problem nail the offending board to the sub floor and are done with it. But our problem isn’t just one or two boards, it’s pretty much all of them. Also, I don’t think we have a sub floor.

I think this for two reasons: I installed a ceiling fan this summer and got a good look at the bottom side of my upstairs neighbor’s floor. It looked a lot like the top of my floor, with about 2′ boards with the ends offset. Since the bottom of his and the top of my floor look the same, this makes me think, that both of our floors are just one layer of boards running perpendicular to the joists. The second reason I think there’s no sub floor is that there are rows of nails (in every third floorboard) spaced 16 inches apart running parallel to the joists.

So, how do fix my squeaky hardwood floors? I noticed that some regions of the floor don’t have the rows of nails, and so I assume aren’t nailed to the joists. And the few places where the floor is quiet is where there are lots of nails. Since nails seem to make it quiet, I was thinking of putting more nails into the floor, like maybe at every joist.

Since it seems like a simple solution, I’m a little nervous about adding more nails, because there may be a reason that the original flooring guys didn’t put nails everywhere. Did they nail every third board (and not every board) to let the wood move a little bit? If I nail more regions down, should I also nail every third board?

A: I have seen a few floors like this installed without a sub floor. Sometimes they did not stop the end of the plank at the middle of the joist, but between them. Not a good thing. This floor may be quite old but should have been nailed through the tongue and into the joist. They likely didn’t have a nailer but used simple 2′ common finishing nails. These would tend to work loose over time, especially if there was seasonal movement. You could try a few nails through the face and see if it helps. Counter sink the head and use colour match wood putty to fill the hole. Use spiral nails, not the ones with the smooth shank.

Edge of floor coming unglued

Q: We had wood floors installed in our kitchen. They put in a transition piece between the dining room and kitchen. The edge of the wood floor unglued and you can push it down. The company drilled a couple of holes and filled it with glue but it is coming up again. What can be done to fix this problem?

A: I would think the drill and insert glue method is a good approach. Did they weigh the strip down after doing that? If this is a nail down installation, could they fire a couple of nails through and fill will colour match putty?

Follow-up: No they did not weigh it down and it is not a nail down. It’s in a very open area that is quite noticeable. The company now thinks they will have to take out the transition strip and re-glue the floor underneath.

Wood planks pop when you walk on them

Q: My house is almost two years old, concrete slab, wood floor B****-Manufacturer (glued down). There is a section of my living room where the wood planks pop when you walk on them. All the pops seem to be in a line (where the concrete floor had a small crack due to settling). How do I fix these pops? I’ve heard that I have to drill a small hole and inject wood glue or a putty, to fill the gap between the concrete and wood.

A: The only thing I can suggest is to use an injectable adhesive. Bostik makes just such a product.