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Tips for Gluing Down Solids on Concrete

By Michelle Swiniarski
February/March 2012
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Glue down wood flooring over concrete? “Are you kidding? No way! Never!” That’s what many said to this suggestion years ago. And yet many adventurous individuals were willing to listen to such craziness and they glued down engineered wood flooring. Slowly, at first, and then with great fervor!

Glue down solid wood flooring? “Absolutely not! Can’t be done! Stop the nonsense!” they screamed! And there from the crowd came the few, trowel in hand, who ventured forward. They had highly elasticized, cementitious products, two-component epoxies and moisture-cure urethane adhesives. The moisture-cure urethanes took the lead and the South was now able to enjoy solid wood flooring installations directly over their concrete slabs. Voila!

There were challenges, for sure. One subtlety that some did not realize was that solid boards used successfully for glue-down installation were not the same as those used for nail-down. Initially this made for some interesting installations in the field, to say the least. Typically, solid flooring used for glue-down installations is quartersawn to produce the most stable board possible.

That being said, all wood flooring is a natural product and will move with varying moisture and humidity levels, and solid wood flooring will move more than engineered because it is not stabilized by alternating directional layers. Due to this movement, solid wood should not be installed in basements since they are below-grade and highly prone to moisture and relative humidity issues.

Before the installation begins, it is important to perform a thorough job-site inspection. Ensure that the HVAC is operational and the job site is completely acclimated to the temperature and humidity at which the room will be maintained when occupied. Test the moisture levels in the substrate and ensure they are less than 3 lbs./24 hours/1,000 sq. ft. (ASTM F-1869) or 75% RH (ASTM 2170). Moisture testing is only indicative of the slab condition at the time of testing. To ensure the condition does not change, the concrete slab needs the proper moisture vapor protection underneath and proper drainage away from the building. If the moisture levels are high, consider an adhesive that performs as an adhesive, vapor barrier and sound reduction product. (But understand that these products are not designed to overcome ongoing moisture issues such as poor drainage, flooding and the like.)

Once the job site conditions stabilize, the wood may be delivered so that it may properly acclimate. Ensure the wood reaches equilibrium (for the long-term RH and temperature of the room) before it is installed to ensure minimal movement after the installation. Consult your wood flooring manufacturer for the recommended moisture content (MC) of the wood, as this will vary by area of the country, wood species and even domestic wood versus imported wood.

Now that we have the proper acclimation and a dry slab, we must look more closely at the slab. Does it have a psi of 3,000 or higher? Is it porous enough? If you drop a bead of water on the slab, is it quickly absorbed? If not, there may be a sealer that must be removed or a non-porous surface (such as burnished/steel troweled concrete) that must be ground down so the adhesive can properly “grab” the concrete. It is critical that the slab is smooth and flat (we don’t want noisy hollow spots to haunt us later), and free of dust and contaminants such as drywall splatter, paint or a previously applied adhesive. Only use high-quality polymer-modified, cement-based patching and leveling compounds.

As many have found out the hard way, wood does move. Ensure you leave the proper expansion space around any stationary objects (walls, counters, etc.). Expansion spacing will vary depending on the wood species, current MC and the expected MC for the location. Contact the flooring manufacturer for its guidelines. It is important to discuss the natural movement of wood with the customer so they establish realistic expectations for the look of the floor and the necessity of maintaining the environment for optimal performance.

Make sure the adhesive you choose is recommended for the installation of solid wood and that you have the appropriate trowel for the specific wood flooring you are installing. The working characteristics of an adhesive will vary from job site to job site due to the type and porosity of the substrate, temperature and humidity and even the trowel size. It is best to test the adhesive in an area to see how it will behave before the job begins to ensure you do not exceed the open and working time of the adhesive.  Periodically during the installation, lift a board immediately after you have placed it to make certain you have 100 percent coverage of the adhesive to the back of the flooring.

Once you have installed the wood flooring, it is critical that you immediately clean the adhesive off the surface of the flooring. Shine a light low on the floor to help find any adhesive smudges. It takes a lot of holding power to keep a solid wood floor in place, and the adhesive will bond as aggressively with the flooring surface as it bonds the wood to the subfloor! The longer the adhesive is on the surface, the more difficult it is to remove, and eventually the only way to remove it will be to sand the floor and refinish it, so remove it early and completely.

Some still say you can’t glue down solid wood floors, even though they are probably standing on one without realizing it. Never say never!


Michelle Swiniarski is director of product market, adhesives, at Boca Raton, Fla.-based QEP.



Wood floor adhesives            Installing wood flooring                solid wood floors   

 Comments:

I would do every thing in my power to avoid a gluedown in the first place. If the home owner still wants a solid gluedown , proceed with caution and know your products. As far as installing solid 3/4" flooring, yes there are glues that say its possible. The real problem maybe, "how can you get a crowned, bowed , warped board tight and keep it tight? Most glue downs are pre-finished and if they dont go down tight the do not look right.
Ed Peti  Owner/floor mechanic  2/18/2012 1:14:20 PM

There is no valid reason to glue a solid floor to concrete.There are plenty of good engineered floors on the market..The RH in the home must be maintained or it will cup. Then you are on your own with a cupped floor that no one will cover any warranty.
Jack Shirley  Flooring Contractor  2/21/2012 11:18:37 AM

Typical responses for such a topic. Gluing flooring down is not that difficult. If the board is crowned, bowed for warped so badly perhaps you should not install it...even in a nail down installation. Isn't this why every manufacture says there can be 5% waste factor in any material? I would recommend knowing your mills to buy the highest quality. There is no valid reason NOT to glue a solid down. The RH in the home should be maintained not matter the construction of the material. It is all wood and will all react to RH and temperature changes. All manufactures state in their "warranty" that RH should be between 35 - 55 % RH.
Kris    2/21/2012 2:33:40 PM

It doesn't sound like Kris has ever nailed a solid floor down.Those that have know how to deal with bowed boards by using the wood sub floor as an achor to pry the borads into place while you nail.Maybe he could explain how to do that with a concrete sub floor. You could throw away half of the customers flooring.It is not worth the headaches and potential failure. Use engineered floors over concrete.
Jack Shirley  Flooring Contractor  2/23/2012 2:52:05 PM

I glue and nail solids to concrete. I agree it's a bad idea but there are ways around it. If you can't use shorts you'll have to subfloor the concrete with plywood using bostics and concrete nails. Then paper the floor and nail using 1 1/2 cleats. If your installing long wide boards , glue and nail. I always recommend solids over engineered. Way better quality, more variety, lengths, widths, American mills, and generally 20-30% cheaper. They make you more legitimate a contractor. All this being said , I still lay a lot of engineered.
Todd  Contractor  2/24/2012 8:58:16 AM

After being in this business for over 40 years I never say never however I don't trust the manufacturers of solid products these days to produce a milling quality good enough for gluing. With 3/4" solid flooring it is normal to expect a small degree of warping or mis-milling that can be pulled out with a nailing gun. Asking the manufacturers to make solid 3/4" planks with tollerances good enough to glue to concrete is beyond their abilities. We will stick to engineered flooring for glue down and stay away from potential disasters. Ron Ander - The Hardwood Flooring Stores Ltd. - Toronto & Burlington.
Ron Ander  President & General Manager  2/29/2012 2:25:44 PM

Seems to me Kris knows what they are doing, Jack has never bought a quality floor, and the rest of us proceed with caution. We have been doing it in the south for years with about 99% success. Never glue anything down longer then 36", and always use aa high quality glue and never do it without a moisture barrier. Also use ONLY qtr. sawn or exotics. People get the idea that glueing solids is a cheap way out, and it really is not if you take that route and then you see what failing floors is all about. This is not one you can skip on anything with, it must go by the book. No, maybe a little over what the book says and you will have success.
M H    2/29/2012 3:39:45 PM

I have glued quite a bit of 3/4" solid wood floors \directly on the slab, but after extensive testing,evaluating climate control of the space and only herringbone or shorts. Further more only handfull of species able to stay problem free. As engineered flooring available as same wear surface as solids, there is actually very small number of applications that would force solid option anyway. _Note: we are pulling 3/8" solid cumaru installed over concrete just 2 years ago by someone, They ended up paying 18K settlement.
Sam    2/29/2012 3:41:47 PM

"Also use ONLY qtr. sawn or exotics" MH. Jatoba will fail for sure even lengths up to 36". Not stable enough.
Sam    2/29/2012 3:48:01 PM

I have been at this for 32 years and counting and shorts in mastic was a standard option at one time and the mastic was actually tar. A bit messy but worked great. Now I use urathane adhesive. The trick if you will is short lengths. But even I generally use an Owens or similar engineered over concrete. It's just simpler and faster. Have fun and be creative, that's what keeps it worth doing.
Philip Hawk Just Wood flooring co.  Owner  2/29/2012 4:57:28 PM

Glue it down! Especially here in the southwest. Our concrete slab floors are pretty dry, so using a quality adhesive is no problem. I would only be concerned about freshly-cured concrete. Have installed standard Bruce red oak narrow strip and 9/16" thick Brazilian tatajuba from LL over concrete with urethane glue with no issues so far. We used whatever random lengths came out of the boxes. I have another 600sf of the tatajuba going into my house soon and it will be glued as well. Just like with framing lumber, if it's that twisted or bowed, don't use that piece! Solid is definitely better if you can get it. Use engineered for disposable floors, I guess...
Nick  Professional Engineer and Builder  2/29/2012 5:21:44 PM

We are based in South Africa and all our houses have concrete subfloors. We ditribute to installers nationwide and use a multi-ply engineered T&G floor on Elastilon stick mat and we have 100% sucess rate. We have over 300,000m2 installed like this and we have zero floor failure. We offer a humidity failure guarantee irrespective of humidity and our humidity swings are from 7% humidity to 95% humidity in the wet season and we have zero problems. We do not offer a solid option exept for our sports floors. Concrete, Plastic 250 micron moisture barrier, Elastilon and Multi-ply engineered floor = 100% success irrespective of humidity.
Steven Suntup  MD Suntups Wooden Floors  3/1/2012 4:57:41 AM

Glue down solid all the time contract a real installer not a jackleg and you wont have any problem.Do it all the time and have never replaced one due to these issues.perform your moisture testing properly is the key use the right adhesive vapor barrier ,do not use cheap solid products from small mills that are not equiped to produce a good product and enjoy your new floor. Jonathan Dingler Certified Installer, Inspector, and Sand and Finish
Jonathan Dingler  Dingler Wood Floors certified installer and inspectorr  3/1/2012 2:09:08 PM

Note the above cumaru floor. Thanks but I will keep the $18,000 and only glue engineered floors to concrete. The only people that benefit from gluing solids are the manufacturers.Good luck with your claims.Of course gluing shorts down can work like always. That is not the issue here.This article is talking about regular random length strip and plank. Very irresponsible and unnecessary.Save your self and your customers the agony of defeat.
Jack Shirley  Flooring Contractor  3/2/2012 4:56:33 PM

Jack, I may not explained right, we are tearing out the cumaru that installed by another company,my client's lawyers made a deal for them to pay 18K compensation to replace. we are going to install engineered. Sam
Sam  Owner  3/2/2012 8:32:49 PM

Sam, You explained it correctly. I think I see the picture clearly. The Homeowner probably had no humidity control in their home and that caused the floor to fail.The installation co is going to pay $18,000.00 out of their pocket when they were told by the flooring and adhesive manufacturer that they were able to glue this solid floor to concrete. Now you are replacing it with engineered.Nothing else needs to be said. There is no reason to glue down solid floors
Jack Shirley  Flooring Contractor  3/5/2012 1:02:44 PM

Why is it everyone thinks the end user is not responsible for maintaining their ambient rh and temp to the manufactuerers and industry standard for controlling movement in the floor? If you buy an appliance or a car or anything else you get a manual and with it there are maintinance guidelines in it. Same with many prefinished hardwood floors, look in the box. When an enduser mis-uses an appliance or car the warranty is void. You don't see the installer of the appliance or car dealer paying for them do you! If your doing a site finished floor why not leave one and have them sign off on recieving it. To many floors have needlessly beed replaced because of mis-maintinance.
groovin  owner/installer/blogger  3/5/2012 3:05:46 PM

Oh and I'd say there are quite a few high end manufacturers out there who allow their solids to be glued on concrete. Not only do many allow it, they advertise it. With the radically changing adjesive technology. Stauf for one, even Bostik say yes with limitations http://flooringblog.bostik-us.com/2009/06/truth-about-gluing-solid-wood-flooirng.html. Basically it all comes down to the milling, type of milled wood, how it is sawn, adhesive and moisture testing with grading in mind as well as flatness of the slab.
groovin  owner/installer/blogger  3/5/2012 3:36:53 PM

Ok ive been nailing down solids since 1996. Basically if you get lower grades or cheap pre finished or as they are called "seconds" you will have warped or as we call them "smiling boards" i started my company in NJ. No concrete sub floors there really. Everything was nailed down. Now ive been in florida for 7 years and its the total opposite. All comcrete slabs. Glue downs and floaters. I would not glue soild 3/4 down ever. Why? When you can get 1/2 in engineered products that are just as good that you can gluedown. If you go the cheap route and get low grade bad milled 3/4 soild boards and try to glue it down you will be in for a suprise. Now if you like waiting around with straps on your lines every 5 mins then have at it. The reason engineered was made was to get the look of soilds with the stability and warranty of a soild. I went from being a nailer to a glue down installer and floater. Not to say i dont still nail down every chance i get. But here in florida 95 percent of my work is over concrete. And also being a sand finish company i know about cupping amd warping. I sand down the mistakes of other unfortunate home owners as well. I feel with my northern and southern experience i pretty much can say with out a doubt. Stay away from 3/4 gluedowns. If you really want to do it or get a customer from up north that moves down south and demands a solid floor. Do as i do. Tapcon 3/4 inch plywood down and use 1 1/2 inch staples to attach it to the plywood. Remember to roll out tar paper before the plywood is down and before you install your soild also. I hope thos was helpfull. If anyone ever has any further questions you can feel free to email me at Thewoodfloordoctor@ gmail.com.
The Wood Floor Doctor,LLC - Florida  Owner  3/5/2012 6:23:02 PM

Heck, why not just get a 3/4 solid engineered 3 ply? Very stable, more so than any 4mm veneer over top of a 7 ply. Resand just as many times as a solid. The people starting to manufacturer those are light years ahead of the others.
groovin  owner/installer/blogger  3/5/2012 9:52:29 PM

I am a consumer in florida with a mostly level concrete subfloor. After a complete laminate disaster, I am having all of it pulled up in favor of real wood. I've been trying every which way to justify putting solid wood down, but I am seeing professional after professional state that solid 3/4 on concrete can have disastrous consequences. At this point, I want the smoothest installation possible with the least amount of risk, so I will be going with engineered. If there's an expert in south florida that can lay down engineered wood *the right way* like it's nobody's business, please contact me at infona @ gmail dot com. The only catch is that I'm locked into using Armstrong product, since they are giving me a credit for the 1600 sq ft of defective laminate. Hopefully they sell a good quality engineered product that will look good and be a pleasure to install.
Sam  Consumer  3/5/2012 11:33:13 PM

There are very good unfinished 5/8 inch engineered floors on the market with thick sliced top layer to give you a solid look without the cardinal sin of gluing down solid boards. Be wary of the exotics. They are prone to dry cupping and delams
Jason Cupps  Installer  3/6/2012 10:45:26 AM

its interest to know how this works in other parts of the world.In Lagos Nigeria i lay straight onto the solid leveled concrete floors and if the floors are a finished floor(tiled or marbled) we lay straight on it and they last for many years. when we finish the floor is solid and firmly tight on the floor but this does not stop the wood from moving, we also don't lay wall to wall there is always a gap at all sides of the floor by the wall.
Seyi Onabule  contractor-installer  3/7/2012 4:21:02 PM

Jason, Care to share your top picks on engineered flooring? I really want to avoid the garbage, but there is surprisingly little information out there to figure out what's good vs what's crap.
Sam  Consumer  3/7/2012 8:41:07 PM

Gluing a solid to concrete is never a good idea. When your customer is interested in solid, it is best to educate them on the dimensionally stable engineered floors that are available. Mirage, preverco and lauzon are all using the Dry Sawn cutting methods. Dry sawn explained below: Instead of boiling the hardwood logs, in this process they are kept at a low humidity level and dried slowly to keep moisture from inside of the wood cells. The manufacturing process to get this top veneer layer is similar to how a solid hardwood is manufactured. This style of engineered hardwood has the same look as solid hardwood, and does not have any of the potential problems of "face checking" that rotary- and slice-peel products have, because the product is not being exposed to added moisture Mirage's top wear layer has a comparable sandability of a solid product and a baltic Birch ply backing ,making it the best quality engineered floor any homeowner can invest in.
S&M Hardwood   Dealer/Installer  3/8/2012 5:18:11 AM

Ther is no reason to accept the Liability of gluing a solid down, once that floor cups or has issues, the dealer or installer is who the homeowner is going to turn to and blame. if you dont educate them that is exactly what they will say when there floor is cupping and needs to be replaced and they will hold you responsible. I work and Live in florida and I have not glued a solid down in years because I will not accept the Liability. I would rather walk away if the homeowner insists on going with the Solid.
S&M Hardwood  Dealer/Installer  3/8/2012 5:23:28 AM

Sam I don't think you would be here iof you were a consumer.Most of the top brands of AMERICAN MADE engineered floors are very good quality. Avoid importers and liquidators. They don't back their products.
Jason Cupps  Installer  3/12/2012 2:55:40 PM

Wow, talk about being all over the map. Quite a range of opinions between nail-down country installers to those from slab areas. After all, it is about perspective and knowledge of current technology. Keeping in mind that the US is one of the very few countries in the world that actually nails down wood flooring. Most of Europe, east and west, lives in and on concrete. Those folks glue millions of feet of wood flooring to concrete a year, and some floating of course, but mostly glueing. Most of those installers have never heard of a wood floor nailer. This does not mean "you" have to glue a floor to concrete or gypcrete. But it also does not mean you cannot just because "you" think it should not be done. There are products available that allow and guarantee such a procedure in the US as it does worldwide. It is really not that complicated. It does require some investigation and understanding of the physics. There is always moisture in concrete, no matter what the age. The issue involves the source of the moisture "vapor" and then stopping the transmission of same. Keep an open mind.
Mike Hodges  product manager  3/12/2012 3:19:34 PM

Jason, I'm not sure what you mean. Either you are doubting that I am a consumer (I assure you, I am), or you are saying I shouldn't be here because this is a more professional-oriented site. Either way, I came across this thread because I'm trying to find an installer here in South Florida that's really good at installing wood floors. I'm also back and forth on the engineered vs solid wood debate, because the opinions are "all over the map", as Mike Hodges pointed out. I've been burned by laminate, and I don't want anything like that to happen on the second try. Solid wood floors would be the most authentic, and add the most value to my home. But how can I forgo so many warnings from all these professionals who are against this type of installation? It's encouraging to hear that Europeans are much more comfortable with solids on concrete, but until I find an installer who is also that comfortable, it's going to be hard to pull the trigger.
Sam  Consumer  3/12/2012 3:39:54 PM

BOSTIK'S FAILURE....Please beware of Bostik's Ultra Set Single Step Adhesive. Bostik's claimed no limitation what so ever on moisture content from slab, no need for moisture test, as long there is no visible water standing. Anyway, we glue down engineer hardwood with this adhesive 14 months ago, adhesive failed to protect this engineer floor from moisture. I also had a 3/8 solid glue down buckling on me, and guess what adhesive underneath it.......ULTRA SET SINGLE STEP.
Alain  installer  3/17/2012 10:08:35 PM

Sam We are all consumers of many things.If you read the above commments by guys who have had jobs fail you will not allow a solid plank floor to be installed in you home without a plywood underlayment. The industry developed engineered floors for a reason.Don't let anyone sucker you into buying their product with a risky installation.If you need a solid look use a 5/8 engineered with a 1/4 inch sawn wear surface. That way you dont have to worry about a failure. You will have the same look and ability to refinish many times.If you are trying to save money by going with solid all I can say is good luck
Jason Cupps   Installer  3/20/2012 2:53:41 PM

Hey Guys, I made a good living doing wood floors in Florida... Think that anything under 36", like the large parquets from Europe... Just have to know how to install it properly... Back in the 80-90's we use to use a FHA vinyl glued to the concrete for a moisture barrier. We would ruff it up then install. We like to take on the higher end of the business. My dads 75 yrs old and he made a great business in north FL. Good luck for those who take it on... Sincerely, Tina Darling Boone www.BooneWoodBrokers.com
Tina Darling Boone  Owner  3/29/2012 2:10:17 PM

Thanks to all your help; I am officially going engineered on my concrete. I am still looking for a reputable installer in south florida!
Sam  Consumer  4/29/2012 1:01:47 AM

Alain - Bostik Failure- Actually there are limitations and directions for this product that need to be followed. Check the product data sheet. Floor must be dry at time of installation and always check for coverage / contact with adhesive by pulling up the occasional board. Coverage must be 100%. Know the product before you use / dis it.
M Keenan  Flooring installer / consultant  6/15/2012 10:17:24 AM

We are in middle Georgia, and currently have engineered hardwood glued over concrete at grade. We have some water issues (discoloration/moisture) that are being investigated -- both areas are in straight lines. I think one may be plumbing issue as it lines up with toilet in bathroom, although it is several feet away in another room. Other area doesn't line up with any known plumbing....still having that investigated. Floor is metering high moisture in about a 2 foot area by ~8 ft long. The reason I'm on this site is to figure out what type of wood floor is the best to put over concrete slab once we get this pulled up, leaks repaired and start over. The hardwood I have now is continuous thru foyer, living room, den, dining room, kitchen, breakfast area and bathroom on main floor. Whatever the issue ends up being, we are trying to educate ourselves on the best options for moving forward with wood on concrete. So I am interested in what should be done to seal concrete, and the best way to install an engineered floor. I don't believe solid would be an option as I believe the sub-floor required would make my floors too high for doorways etc. I will definitely look for made in America flooring, but any specific brands that are good would be helpful of both flooring and the best sealant/glue that you guys know of? Will be looking for an installer also but I don't know the ones in this area so I'm trying to make sure we have some information before we get in those discussions.
June  Consumer  10/17/2012 4:30:07 PM

Nice post. I was checking constantly this blog and I am impressed! Very helpful information specially the closing part I deal with such info much. I was looking for this certain information for a long time. Thanks and best of luck.
Concrete Crack Repairs  Owner  1/3/2013 1:30:50 AM

Hello to All and happy New year Nice article and very close to the point , very deep!!! In my case i am on this stage of bulding and i would like to put solid wood especially American white oak 12 cm width and 22 mm thickness my flat is on the first floor and i have concrete so it will put with glue also plywood no space to enter!! Αfter reading all of this reviews i am afraid to do it. Note that i live in Greece Athens if this means sth for moisture levels. Please i am wating for your advices. Thank you in advance
Nick  Accountant  1/3/2013 7:12:36 AM

Alain, re: Bostik failure- So what did Bostik say about this? The only time I've seen this glue fail was due to improper trowel application which left voids in the glue once the boards were set. This was discovered when the material was ripped out and you could see the glue was missing in some areas between the ridges.
EM  Distributor  3/28/2013 4:21:05 PM

I live in a condo and must have cork as sound barrier. I had engineered floor glued down and it failed. The remodel is not finished and the flooring is being removed. I think I should go with solid wood since the engineered failed but I have height restrictions. My flooring installer said he can glue the solid but the store said solid can only be nailed. I'm confused what to do since the mfg failed. If I go with solid wood glued is it cement>glue>cork>glue>floor. Or if its nailed is it cement>floating cork>floating plywood>floor nailed. What failed was Bruce engineered flooring with install being cement>glue>cork>glue>mfg wood. I appreciate suggestions.
Vickie  Retired  4/3/2013 7:34:05 AM

All of you guys talking about glueing solids (not shorts), find me one adhesive manufactor that will "in writing" guarantee the glueing of solids? Correct, no one from Franklin, Bostik or Stauf chemicals will! If I am not mistaken the NWFA does not recommend it either. Now Sika Adhesives offer there foam matting system with adhesive sausages and they will guarantee silids over concrete.I know factual Bostik and Franklin Adhesives will not. Also Vickie did you buy first quality flooring? What species? Why did it fail checking or delamination? I would reccomend using a good rubber foil pad underlayment with a rating of 72 or higher and floating the floor. We have this underlayment specified in alot of high rise buildings for the purpose of sound absorbtion.
Tim  Importer / Distributor  4/3/2013 2:57:44 PM

Question- the concrete slab tests at 3 pounds per 1000 sf. The HVAC is fully operational as required by the manufacturer. The solid flooring is glued down.What is the EMC of the solid flooring 6 months after the installation is finished?
David  Owner  4/9/2013 7:31:59 PM

Basically everyone has their own preference due to their own benefits pastexperiences. But in the end, no one can convincely say it can or it can not be done. At least did not find any rule say "DO NOT". Then why bother.In realty is, you do your way and I do mine, isn‘t it?
Andy  Contractor  6/23/2013 3:00:53 AM

Hello all and thank you for all the information. I am experiencing a horrible situation with Brazilian teak 3/8" over concrete slab. Manufacturer Bellawood from Lumber Liquidators Home owner hired me to pull out carpet and install wood. Pulled out carpet waited 3 weeks, brought wood to the house, spread out the boxes throughout the house and opened them, we let the wood acclimate for over 2 weeks. I did moisture testing throughout the slab prior to install and readings were all within the allowable moisture amount according to Mapei 995 moisture barrier and adhisive 2in1. L.L. Sold the, the wood and adhisive/moisture barrier assuring the that that is all they needed. They paid me $5,400.00 to install the wood, very low price because they were "friends" 2 months after they called me saying that the flooring started cupping throughout, I ran over to their house and saw that all the wood flooring was cupping and had failed throughout! We installed the wood towards end of winter. I called a National hardwood flooring inspector to give us a explanation and he said that it was a site related issue due to the homeowner not using the HVAC system in the house explaining how the drastic tempature and relative humidity changes caused the floors to fail. The home owner is now trying to sue me and is asking $24k or he will do his best at ruining my Contractors License. I offered to supply him the labor no charge. He is still trying tu sue!!
Michael C.  2400sq' Solid Brazilian Teak gone bad  7/19/2013 6:21:06 AM

Michael, It can be worse to acclimate during the heating season!!! The wood drys out and you install it tight. Come spring time, the heat gets turned off and the humidity(moisture in the air) rises. The wood absorbs that moisture and the wood cells swell. The wood edges compress against each other and you get a cupped appearance. Acclimation is not a time thing. It is a moisture thing. A pin-type wood moisture meter will tell you if the wood is acclimated and which way it needs to go for year around problem free wood floors.
Floorguy    7/22/2013 5:14:38 PM

Man, that 3/8" solid they sell yells "Run away" to me. It's half the thickness of 3/4", so any expansion will be done throughout the entire thickness of the board, rather than at the bottom first like a thicker board. I'm betting that since the wood is 1/2 as thick as 3/4" solid, it's nearly twice as sensitive to moisture as the thicker solid. Add to that the density of the flooring, and you have a lot of pressure building up. So, regulation of moisture in relation to installation conditions and living conditions are twice as critical. Floorguy has a point -- the wood was allowed to acclimate to the interior conditions of the winter heating season -- most likely low interior RH, therefore acclimating would lower the MC of the flooring. That said, if the homeowner is not using HVAC during the summer, and the interior RH is above the recommended RH level set by the manufacturer, I don't see how the installer can be fully to blame. The purchaser of a product, in this case the homeowner, has a responsibility to read the directions, just like the installer. If the living conditions of the home are not in accordance to the manufacturer's guidelines, I would think the responsibility falls on the one who regulates the living conditions.
Tom Werner    7/25/2013 1:55:17 PM

You can pull a glue down flooring together with straps its very easy solid flooring. I spent 20yrs up north nailing and 10yrs in Florida gluing. The right tools and product and testing and you can do anything
Tom    9/20/2013 9:39:08 PM

We just got done gluing down 3000sqft of 3/4 x 8 white oak flooring to concrete. The boards were 4ft to 7ft long. All the testing was done and we used bostik singlestep glue. The floor looks great. We have been in business for over 92yrs and spent 80yrs up north nailing down. We been in Florida for 12yrs and if it works in Florida, it can anywhere. Just be smart test and test and test again AND USE BOSTIK SINGLESTEP. I wasn't a believer to now. The floor sits in the lobby of Streamsong Resort
Tom  Courduff Hardwood Flooring Co.  1/10/2014 10:23:12 PM

Tom @ Courduff, I'd love to chat with you. I'd normally NEVER glue down a solid wood floor. Yet I'm about to buy a house in which most of the floor is 3\4 inch solid red oak, 2 1/4 wide long planks ALREADY glued down on concrete. My wife wants wood in all the remaining bedrooms. My choices are to pull up all the floor in the house and install new (umm...no!) OR to continue on with what we've got. Any tips, tricks, advice? The existing floor looks nice, but I see movement. I don't know how old the floors are, but the house was a rental so there may not have been careful maintenance. The house is located in Orlando Florida. It sits above grade. Any advice is greatly appreciated!!!
Ray Brown  Installer  2/25/2014 6:41:42 AM

I'm looking at having wood floors laid over a concrete slab in rainy Seattle.. We're on the "ground" floor of a 1989 4-story condo built on a hillside with our entry being at grade and our unit extending out over a commercial space below; our parking garage is behind and up the hillside from the entry to the complex and our unit. Our current floor has what appears to be nailed down 3/4" solid 2 1/4" wide white-washed red oak in the entry and kitchen with carpeting throughout the rest of the unit. We'd like to keep the existing wood and lay new floors in the remaining areas then refinish to match. Keeping a level surface between the existing and the new wood is particularly important for me due to mobility issues. This was done successfully with a glue down solid hardwood installation over a cork underlay in an upstairs unit where the carpet was over gypcrete and it looks great. That installer recommended the same approach over the slab for us using shorts. Another installer suggested gluing regular length solid wood directly to the slab without the cork (unlike the upstairs unit we are not required to use cork for sound dampening). A third advised against sold wood altogether, not for reasons of dimensional stability so much as what he described as less surface area with tongue and groove available for adhesion, and suggested a more expensive 3 1/4" wide engineered product glued down over cork. All three claim the glue itself will serve as a moisture barrier. Since we are on the slab in a notoriously damp climate dimensional stability does seem like a legitimate concern; additionally, I use power wheelchairs which can weigh in at up to 600 pounds -- the third installer said that the glue down engineered would be better able to take that kind of pressure than glue down solid hardwood flooring. Any advice would be welcome.
george  homeowner  3/8/2014 3:29:25 PM

I should say: the first installer proposed using short lengths -- 3 1/2 feet and under -- not "short" grade. The proposed grade is "select".
george  homeowner  3/8/2014 3:48:25 PM

George-I work just south of Seattle in Pierce County. I would recommend using a solid product without the cork to maintain the same height as your current floor. Lengths and grade would be more of a personal preference. Solid material would hold up better to your wheelchair traffic because a thin wear layer of an engineered product is usually backed by a softer wood and thus easier to indent the floor. I probably wouldn't use the 3rd installer. If they use a 2-in-1 glue such as Bostick's single step or similar then a moisture seal shouldn't be needed.
Joshua Crossman  Owner PTL Hardwoods  3/10/2014 3:14:56 PM

I am about to glue down solid bamboo over concrete (30 year old concrete in houston texas. I am using a moisture barrier urethane glue that is made specifically for Solid bamboo flooring. Any issues I need to know about?
Joe  Owner  6/2/2014 10:07:41 AM

Joe, I would highly recommend you check out this article about bamboo: http://hardwoodfloorsmag.com/articles/article.aspx?articleid=1674&zoneid=2
Kim Wahlgren  Editor  6/2/2014 1:52:00 PM


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