Yes. Glue assist is required for wide plank floors. It’s NWFA standards. Which rule over any builder practice or personal preference. Read the manufacturer’s instructions about the required testing of humidity levels and everything else. You should also calculate the deflection of that subfloor and joists.

https://nwfa.org/wp-content/uploads/2020/03/JobSite-Checklist2.pdf

I put rosen paper under and nail. If in doubt ask your flooring manufacture. You have to acclimate the flooring and may be wait 60- 90 days after drywall is finished.

If you ever want to change the floor though, if it's glued, you're going to rip up the subfloor - granted that wouldn't be for like 25 years. I thought glue was bad for floors since it stops them expanding and contracting?

Nothing stops wood from expanding and contracting but precise indoor humidity control. If you want to argue with industry standards, call up the manufacturer and the NWFA.

But unless you follow industry standards, including the required documented moisture testing, you have zero warranty and will be buying all new flooring a lot sooner than you think you will.

A properly installed wood floor’s lifespan is well over 130 years, if treated with proper respect, and not 95 gallons of mop water after gravelly shoes walked on it. Not to mention the ridiculous changes of color because of fashion rather than finish wear through. A floor is not a pair of drapes that you get tired of and donate to Goodwill or attempt to dye another color. A floor is infrastructure. Like the house’s studs and drywall.

Never understood the love for hardwood when you gotta baby them or they will get messed up. If you want to change them later, I recommend getting some LVP. Much more forgiving and they don't hate you if you waste water on them. They don't whine if you step on them with boots. They don't scream if your pet runs across them for their toy. They don't bawl if you kids smears syrup all over them(true story). I HATE wood floors(had them in our last home and would never buy them again)! They are not meant to be lived on. xD

But to answer your question, yes you can either float them (making sure your OSB is level and whatnot) and use nice "thin" foam underlayment(which will pay off down the road when you walk on them....trust me) OR glue them down to the OSB(again want to make sure this is level to account for movement). Will need to rip them up later if you want to change them. OR you can lay LVP right over once you realize it reigns superior. xD

I am sure you know how to lay hardwood down perpendicular the floor joists assuming you are in a multilevel home. ;)

No, you can not float 3/4” solid. Or any of that other nonsense about 5 minutes of plastic being superior to 130 years of wood.

Industry has evolved. We can now float 3/4" solid hardwood floors with Elastilon glued down floating system.

And to be CRYSTAL clear, regular OSB (the cheap stuff, not the subfloor rated OSB) is NOT something you glue to. It is also something that does not like being nailed into (it LOVES to shrink and cause loose nails = NOISY floors. Read the installation instructions. A well written set of instructions will CLEARLY spell out the how and then when.

Many OSB products are NOT allowed underneath a nail/staple/glue down floor. A few are. You have to make sure YOUR OSB is the RIGHT TYPE. If it isn't, your warranty is gone before you nail down the first plank.

And the installation instructions for a 5" wide 3/5" hardwood will also state whether or not you are required glue assist or full spread adhesive.

I highly recommend you read the installation instructions before going ahead. It sounds like you will need some guidance with this install. The installation instructions are written to ensure the owner is happy with the floor they purchased (assuming the instructions were followed by the installer).

130 years of wood that can warp with unnoticed spilled cup of water. Hardwood is not meant for people who have kids and pets running around. No young family wants to deal with this. Every person I talk with who has hardwood flooring wished they put in LVP. I had hardwood floors and it only takes one time to scuff them or ruin them. Now, we made sure to put LVP through over 2200sf+ of house because hardwood floors were/are a nightmare.

Lastly, OP if you don't give a hoot about warranty then proceed. Hardly anyone even uses flooring warranty because they usually have some type of asterisks to weasel their way out. Guess what my neighbor did with their glued down hardwood? Ripped them up(voided their "Warranty") and put down LVP :D

If you haven't done this before OP and have no idea of the things to consider when putting this (HW) down; either watch hours of Youtube, Google, call an experienced friend/family member OR call a professional(expensive route but may be worth it for you). ; )

Nail-only into OSB?

And honestly - since we started doing kitchens in hardwood, I have gone to even bathrooms and laundry in our current house.

Listen, there will always be wood lovers and vinyl haters. And apparently wood haters and vinyl lovers. And different climates.

My last house had nailed only wide plank 3/4 walnut on typical floor rated OSB (Advantech). Did great. Scratched like the dickens and that drove me crazy but no issues with no glue.

I am completely embarrassed that I am not sure what my varying width, engineered floor is now. Definitely nailed but not sure if it is also glued.

I am not sure that average house life expectancy is 130 years (we just tore down a 70 year old one). And I am not sure that Vinyl couldn't last 70 years. Plastic in general lasts forever and wood never does (but that doesn't mean anything really).

I still don't really get why glue is necessary since the tongue and groove holds the wood down on both sides. However, if it's glue assist from a caulk gun in a "s" pattern then it's not so laborious to do. Troweled glue would be a real pita.

L shaped nails should hold just fine in OSB. It's stronger than plywood. I have standard subfloor osb

130 years of wood that can warp with unnoticed spilled cup of water. Hardwood is not meant for people who have kids and pets running around. No young family wants to deal with this. Every person I talk with who has hardwood flooring wished they put in LVP. I had hardwood floors and it only takes one time to scuff them or ruin them. Now, we made sure to put LVP through over 2200sf+ of house because hardwood floors were/are a nightmare.

Lastly, OP if you don't give a hoot about warranty then proceed. Hardly anyone even uses flooring warranty because they usually have some type of asterisks to weasel their way out. Guess what my neighbor did with their glued down hardwood? Ripped them up(voided their "Warranty") and put down LVP :D

If you haven't done this before OP and have no idea of the things to consider when putting this (HW) down; either watch hours of Youtube, Google, call an experienced friend/family member OR call a professional(expensive route but may be worth it for you). ; )

Well tell that to the 90 year old wood floors with inlay in my first house. We moved when my son was 4 and my daughter crawling and then walking at 10 months. Those floors were in perfect condition and I never babied them.

Or how about our 100 year old floors in our second house that were refinished and again, I never babied them at all.

Maybe if you chose a quality wood floor you wouldn't have the problems you mentioned. I've now had wood floors in every house I've lived in and have never had a problem. Do they get scratched and scuffed? Of course. But so does LVP

In fact when my friend and I were building our houses here by the water, he insisted he was putting down LVP for all the reasons you stated and I decided to put down engineered white oak hardwood. Now 3 years later, he says his one regret is that he didn't go with the engineered hardwoods because even though he chose a very high quality LVP (in a $$$$$$$ house), it's starting to peel and discolor.

Plus LVP is made from petroleum products. Not something I want either.

Hi Chispa and Carey. Which manufacturer have you had success with?

Glue assist is needed because a wide plank wood floor is UNSTABLE. The wider the plank the more plank there is to CURL in the presence of HUMIDITY. Yep. Just the humidity in the air can cause it to crown (when the centre of the plank sits higher than the edges) or the humidity in the basement/slab/subfloor/crawlspace will cause it to cup (when the edges of the plank sit higher than the edges).

Water is the most damaging force on earth. Water carved the Grand Canyon. It created the ice caps. It created U shaped valleys when the ice age retreated. It can cause your house to sink. It can split a granite megalith (it's how the Egyptians made the massive granite slabs cut away from the mountain side).

Just because moisture is in the air (humidity) doesn't mean it is inert. Wood EXPANDS in the presence of water/moisture. The wood expands ACROSS the grain (not so much the length of the plank). A plank that is expanding can 'pop' the nails right out of OSB (OSB can have really 'sh!tty' grab...it can be right horrible). The glue-assist offers more stability across the WIDTH of the plank (something is trying to hold down the plank ACROSS the entire width...thereby trying to keep the plank 'glued' the the subfloor.

And OSB does NOT like to have glue applied to it (Advantech is different). The waxes and adhesives in OSB make it very difficult for glue to 'grab'. That's why smooth faced plywood (subfloor grade) is required for nail/cleat/staple/glue down wood floors.

Please CHECK your OSB grade...and then check to see if the wood you have purchased (and the glue you need to use) is allowed to be paired with the OSB you have. Be prepared for "No" as the answer. Because it is a very strong chance that's what they manufacturers will come back with. You might luck out and have the correct OSB...but you might not. Be prepared.

It's APA sturdiflor truflor rated

TruFlor is suitable for carpet, wood strip or parquet flooring (must be installed to manufacturer’s and/or NWFA instructions)

Another question. Most recommend putting black tar paper down before nailing the flooring. Obviously you can't glue to the paper, so you just forego the paper and instead suffer moisture problems from the crawl space?!

Do you not understand that polyurethane glue is what is used direct to moisture laden concrete slabs all the time? It’s a moisture barrier and adhesive both. If you have a moist crawl space, you’ve got big giant problems of another kind. The crawl space should be encapsulated. Is required to be encapsulated as semi conditioned space. That must be addresssed first, or the whole rest of the house will have major issues. Who on earth is in charge of this build? They do not seem to be very qualified.

It's OSB not concrete that the wood floor is going onto. None of the crawl spaces around here have vapor barrier as most of the buildings are 100 years old. I could put one if needed or just dehumidify the crawl

Apply a roll on polyurethan/epoxy vapor retarder/barrier. Then glue on top.

Hire a better contractor here. Whomever you have doing the job is unqualified.

It's flooring, hardly rocket science. If the crawl space is not encapsulated, which it won't be any time soon then polyurethane seems best. Air exchanger will be on.

We just had 7.5" wide by 1/2" thick engineered hardwood installed in our new house. We live on a river with lots of moisture, particularly in the morning when the fog is thick, so we erred on the side of caution and had our floors glued down AND nailed over the top of our Advantech subfloor. We have a basement so some people said the glue down is overkill but again, we didn't want to have any regrets. It cost us about $3K extra for the glue down but to not have squeaky or cupped floors, it was probably worth it.

Evidently it is rocket science to some that cannot read and comprehend manufacturers instructions, or industry standards that were provided. And standard construction industry details. Which is why your installer is completely unqualified. He should be informing you of all of this. You should not be online searching for any of this. It should be second nature to him.

We cannot afford to put vapor barrier in the crawl space right now due to labor costs so need another solution. The vast majority of crawl spaces do not have this in old houses.

And the vast majority of old houses have narrow boards, and still have moisture issues. It’s a much bigger functional home maintenance issue to be taken care of than luxury cosmetic floor cladding. It’s a misplaced priority to concentrate on luxury decorative products rather than functional home maintenance and moisture infiltration prevention. You can’t afford to not manage home moisture infiltration. That’s when it gets really expensive.

@qwertyjjj, how wide would your flooring be? I saw thickness but I never saw width given in the OP.

JuneKnow is correct, no matter how badly you may not want to hear what they say. If you're not going to glue down, which you should, you should put a moisture barrier in the crawlspace. If you can't do that, glue it down as the glue acts as a moisture barrier. Doing both would be ideal but.....

Don't skimp on this. We are currently staying in a cabin on our property while our new house is being built and it has 5.5" walnut plank floors. They are beautiful and rustic BUT they were only nailed down into the subfloor by the previous owner with no glue and no moisture barrier under the house in the crawlspace. Guess what? They floors cupped this summer in the humidity. Not horrible but certainly enough to notice. This winter, they will shrink back to normal. The unevenness that the expansion and contraction leaves fits into the character of the cabin but it's certainly not something I'd want in my regular home day in and day out.

By the way, the link in post 2 is just a checklist - it doesn't give any instructions on how to do anything. Is there a link to the nwfa install guidelines, crawl space, vapor barrier. Every installer round here seems to use Rosin paper. That's why I'm asking, you cannot glue to

If you want to skip the glue you can always add some screws and plugs.

Your installer should be well familiar with ALL of this. https://nwfa.users.membersuite.com/shop/store/browse

https://www.buildingscience.com/documents/information-sheets/crawlspace-insulation

Every installer round here seems to use Rosin paper. That's why I'm asking, you cannot glue to

They use rosin paper in my area, too, if it's not a glue down. However, using glue negates having to use rosin paper and is MUCH more helpful at keeping floors from cupping, warping, and squeaking.

Sigh....0h dear. "If the crawl space is not encapsulated, which it won't be any time soon then polyurethane seems best. Air exchanger will be on."

I'm going to ask a simple question: How much will it cost you to redo the floors in 2-3 years time?

An unsealed, unconctrolled crawlspace is against NWFA requirements. It voids your wood flooring warranty and it will void the adhesive warranty. I know the cost is bigger than you want, but it will cost more to redo 'soaked' wood floors. By the time you catch the soaking wet wood, you will need new subflooring as well. And you will STILL have to pay to have the crawlspace encapsulated.

You can skip it today, but it is only a matter of time before the floor fails. A wide plank product is going to cup very quickly...even with moisture barrier adhesive. It just takes more time. By the time it shows up, the subfloor will be soaked and will need replacing.

By skipping this today, you are at very high risk of having to pay quadruple the costs later on. If it were me, I would throw down a vapour retarder (plastic sheeting with holes in it) and a floating laminate floor with a nice underlay (cork is my favourite) and WAIT until I can afford to encapsulate the crawlspace before purchasing wide plank hardwood.

It is your choice. But this is not going to be covered by anyone's warranty...including the installers labour warranty. The conditions are completely wrong for hardwood install.

I installed over 2500sf of solid strand bamboo in my new home 7 years ago. With 3 dogs constantly running in the house. Not one issue. That is unheard of with typical hardwood. The floors look as though i just installed. Plus we live on a small farm so between the dogs and ourselves you cannot help but bring in dirt.

Carpet is disgusting. Vinyl is cheap looking.

Just purchased solid strand eucalyptus for the master bedroom. Cant wait till its installed.