Well, 'plain sawn' has nothing to do with it. If it's engineered flooring, as you said, the surface is only one of many plys of wood in the floor, So the way one ply is sawn can't have any greater influence than all the rest of them.

I agree with tatts but I am not an expert so what do I know:)

What makes up your subfloor? What’s the joist spacing?

IIRC acclimation takes about 2 weeks (but that is recommended for full "finish in place" hardwood). But engineered should be more stable.

Have you called the manufacturer?

That humidity level seems super reasonable, btw.

Could you provide the name of your floor. I took a look at the Mannington site and there are so many.

@ryansnow. Thanks. I was typing quickly and made a mistake--I have edited it to reflect the total thickness of my product is 9/16". The wood veneer is only 1/8" thick. @jannicone that could explain some of the problems. Thank you. It was only acclimated for three days. @PPF it's Mannington Normandy https://www.mannington.com/Residential/Hardwood/Hand-Crafted/Maison-Normandy/MSN07CAF1 @Sammy the subfloor is made up of OSB. I jumped in the attic and measured the joists. They are 22.5" OC, 24" Total. @jeffrey r. grenz Yes, all of the walls were being finished. So being a wet process, would that make the humidity skyrocket so the floors would have acclimated to an unusually high humidity level instead of what's normal in our home? Would make sense because the wood has contracted so much, thus, the gaps. But I still don't understand the gaps along the length of the wood?

Thanks. I was typing quickly and made a mistake--I have edited it to reflect the total thickness of my product is 9/16". The wood veneer is only 1/8"

She edited her post Cinar

What is the thickness of the subfloor? With joists spaced at 24” OC, your subfloor really needs to be beefed up from the standard 3/4” plywood.

@sammy interesting. I will find out. Thank you

@ryansnow I'm not sure but I will look into that. And no! I'm a skinny 105lb girl. LOL

I assume you’ve seen this?

I don't have a laminated flooring BTW. Maybe that's the disconnect?

The process for making engineered flooring and plywood is a process of laminating layers together. Plywoods are laminates, as is engineered flooring, it just isn't marketed as a laminate.

@sammy OMG! You figured it out! This is why I loooooooove Houzz. Thank you so much! For anyone else wondering about this particular issue, here is what I found so helpful in sammy's link:

With the sales growth of engineered hardwood in new home construction, Mannington is aware of some changes in the construction process of building these homes. For many years, the standard in the industry, for joist spacing for sub- oor construction, was 16” on center. This was a time tested, consistent procedure when building new homes. This joist spacing, along with a 3⁄4” plywood sub oor, gave a solid foundation for ooring to be installed.

The new materials that are being used today, Engineered Joists and OSB, allow the builder to make some changes in how these houses are being built. The new engineered joist systems, allow the joist spacing to be increased from 16”
on center, to 19.2”, or even to a distance of 24” on center. This extra spacing on the joist system, without any increased thickness in the sub oor, can potentially contribute to some increased de ection of the sub oor. This de ection in the sub oor, can cause movement between the tongue and
the groove of the hardwood panel, causing a squeak or crackle noise when the oor is walked on. Some hardwood manufacturers recommend that any sub oor over joist spacing of 19.2” or greater, should be at least 1 1/8” thick. Where this is possible, this may reduce the potential for squeak and crackle, as the sub oor will have less de fleection, or movement.

/sigh....

Your floor is bouncing and your flooring guy can't figure out what is causing the gap...

Good luck with your flooring contractor...

Your "gap" problem was probably related to installing the floors while plastering ( I assume that's what you mean by "smooth-coated").

"During installation our home was also being smooth-coated so the humidity level was higher than normal".

It sounds like you improperly installed, at an inappropriate time, laminated plywood flooring on an inadequate subfloor.

https://www.mannington.com/Residential/Hardwood/Installation

If you want it done right tear it up and find a qualified installer to install the new product on an appropriate subfloor.

Or live with it, in no time it will look and perform like an antique floor...

@springtimebuiders I did edit the thickness of the wood floor because my info was wrong in an initial reply. Moving on, double checked the floor from a downstairs bathroom that's being renovated. The joists are the same distance apart, 24" @ksc36 Yes! It was definitely a combination of a bunch of things that were done wrong. My installer was qualified and insured. Not sure why he did things this way but we will be tearing it up and starting over on a subfloor that has been built up to accommodate for the 24" joists, acclimated for a much longer period of time, and at a time when RH is within our normal range.

Cheers and thank you again to everyone who helped solve this problem!

tatts is a good poster who almost always makes solid suggestions and is, in my opinion, never rude - just straight forward.

Anyway, the problems were MULTIPLE...and the layering of an engineered hardwood (top layer laid over a diagonal layer, layered over a perpendicular layer, etc) means that engineered hardwoods do not follow the *solid hardwood properties of expansion/contraction.

The engineered products are inherently more stable....but they can and will move. And a 7" wide product, whether or not it is engineered or solid, is still a BIG plank of wood that will move A LOT MORE than a 3 1/4" wide plank.

So...the issues here (again there were multiple issues):

1. 24" on-centre-joists with an inadequate subfloor thickness (this is the *fault of the house...not the installer).

2. The 'wet' conditions of the reno work ++increased humidity (well above "normal living conditions"). Wet conditions are the *fault of the home, not the installer.

3. Wood was acclimated in and during 'wet work' (this is the beginning of 'installer error').

4. Wood had a SHORT acclimation time (3 days is not normally enough...no matter what the sales people/installers say). This is definitely on the side of the installer error.

5. Moisture Content (MC) of the wood floor was not documented and therefore could not be monitored during the 'wet' storage and was installed when too 'damp' = installer error.

6. Install used staples only (as far as I can tell....please correct me if I'm wrong...I have not seen the word "glue" used in any of your posts). The Mannington statement page (thanks to Sammy for that link!!!) makes it clear that glue assist (that's what it is called when you use glue AND mechanical fasteners) makes everything MUCH MORE stable.

Whew. There you have it. As far as I can tell, this is the whole thing in a nutshell (or a single post...either way).

I would say the home/owner needs to pay for the extra layer of plywood (cost of product and labor to lay it) and needs to pay the small up-charge for the "glue assist" install. The installer gets to take all the other issues on to his/her shoulders.

Please let us know how the reinstall goes.

SJ McCarthy, I think I disagree with you on a couple of points. You said:

24" on-centre-joists with an inadequate subfloor thickness (this is the *fault of the house...not the installer).

Apparently it was not difficult for the OP to determine the joist distance - the installer should have been able to find this out too, and inform the homeowner that a different subfloor was required.

The 'wet' conditions of the reno work ++increased humidity (well
above "normal living conditions"). Wet conditions are the *fault of the
home, not the installer.

Did the installer not realize that this work was going on? Was the increased humidity level in the house noticeable? Was the smell of skim coat apparent? If so, the installer should have known to wait for more favorable conditions before beginning install, or inform the homeowner in advance that "wet" work should be completed after the flooring was installed.

1. Thanks @sjmccarthy

   Yes, lots of issues you summarized quite well! I do however feel that without knowing the backstory it's hard to place blame. It is disappointing to hire a professional and then have so many problems. Isn't that we hire pros?? Because they are the ones who know the ins and outs of what they are doing??

   Here are the deets in response to the conditions you faulted on the home's end. Let me know what you think after you read them. Thx

   1.

   24" on-centre-joists with an inadequate subfloor thickness (this is the *fault of the house...not the installer).

   I hired a professional who should have read the installations instructions that sammy posted from Mannington clearly stating you should build up the subfloor and/or use glue along with the staples if you have joists spaces 24" apart. I feel like I would have just followed the directions if I were the installer. It was a characteristic of the home with specific installation instructions from the manufacturer. He ordered the wood. He had those instructions. He didn't share them with me and I didn't expect him to. I hired him because I'm not in the business of installing floors and telling him how to do his job. Fault of the home or installer?

   2. Shouldn't the expert be the one who knows when a proper installation time would be and about current conditions that could affect it? Or should I have known that? Everyone seems to agree you should trust the pros. Well this is why questions are asked. Funny thing tho, I actually asked him if the humidity would be a problem. Should he be acclimating and installing wood flooring while the smooth coating was happening. He told me not to worry about it. It won't affect anything. I'm going with his fault on this one.

The rest we both agree it was the installers fault:

3. Wood was acclimated in and during 'wet work' (this is the beginning of 'installer error').

2. 4. Wood had a SHORT acclimation time (3 days is not normally enough...no matter what the sales people/installers say). This is definitely on the side of the installer error.
3. 5. Moisture Content (MC) of the wood floor was not documented and therefore could not be monitored during the 'wet' storage and was installed when too 'damp' = installer error.
4. 6. Install used staples only (as far as I can tell....please correct me if I'm wrong...I have not seen the word "glue" used in any of your posts). The Mannington statement page (thanks to Sammy for that link!!!) makes it clear that glue assist (that's what it is called when you use glue AND mechanical fasteners) makes everything MUCH MORE stable.

Thanks for your input. I really do appreciate it.

AnnKH thank you! I was typing my reply at the same time. We are on the same page.

@bennyben75 He told me engineered flooring behaves differently. Which is correct as @MJMcCarthy pointed out "the layering of an engineered hardwood (top layer laid over a diagonal layer, layered over a perpendicular layer, etc) means that engineered hardwoods do not follow the *solid hardwood properties of expansion/contraction."

Because solid wood doesn't move the same way engineered flooring does I chose to trust his knowledge that the impact would be insignificant. My bad for not questioning his every move and trusting the expert.

@bry911 I was reading through the comments so I could gather my thoughts for the flooring guy when I came across an old comment of yours that is incredibly helpful. Why did you add an essay to an old comment and not just post a new one? I'm not sure I ever would have seen it and it's very good information. Explains the longitudinal movement. I was stumped by that one. FYI, never said plain sawn lumber is the most stable, just thought it was important to the discussion. And I'm pretty sure we have agreed on wood movement the entire time. Also, not sure where you got the floor is bouncing from. It just makes a cracking sound once in a while. As for the floor, it's not something to get upset about, just a floor and can be fixed thanks to all the feedback I received.

Your new info is amazing. Exactly what I was looking for earlier.

Wood moves radially, tangentially, and longitudinally. Flat (plain) sawn lumber has the most widely varying grain pattern and therefore moves in the most directions.

You appear to be asking why your gaps are happening at the end (longitudinal movement) rather than across the width. Which is a fair question, the most obvious answers to that question are poor layering of your core material, or that it isn't and you are just noticing it more on the ends of long boards and not noticing the gaps on the width as there are more of them.

In essence, plywood gains dimensional stability by coupling tangential movement to longitudinal movement. Since longitudinal movement is much less than tangential movement (trees swell fatter with water rather than taller), this increases dimensional stability by limiting the amount the wood can swell without breaking the adhesive bond (that is why really thick face layers can be bad as the force of the movement overcomes the bond). In good plywood the grain is rotated many directions and so the wood has longitudinal resistance in all directions. However, poor plywood can actually increase longitudinal movement if most of the core layers are between 60° and 120° of the face layer you will see an increase in length shrinkage and a decrease in width shrinkage.

Modern plywoods often use some composite core but those cores have the same quality issues. MDF is usually very dimensionally stable, while any of the chipboards can suffer from quality control issues.

All of this means that the face layer and its quality are at the mercy of the core layers and their quality, which is what Tatt's said originally.

-------

Of course, it can be the movement of the subfloor too, but a hardwood installer shouldn't be stumped by that. If your floor is bouncing a lot as you walk on it, then the floor is going to move, but your installer should have noticed that.

Why did you add an essay to an old comment and not just post a new one?

The comment you are referring to was posted in two parts on my cell phone. It only added detail to something in my first post, if you notice the two say the same thing, only one uses a lot more words. It was posted in two parts because I got a call on my cell phone and didn't want to retype everything. Immediately after the call I finished the post (it was just adding details to simplify the explanation).

Sorry about that...

Great threads guys. As someone who is moving to engineered with the next house, it is great to see what issues can come up.

What our builder mentioned is that sure engineered is more stable - but you are asking it to do a lot more - like really wide planks. Really wide planks are always more of an issue. I am living with a 2 1/4 plank right now that is 35 years old in a leaky house in NC - like huge humidity swings. Zero gaps.

David, that is one reason I wouldn't want planks over 5". Initially I wanted 3" planks but couldn't find the color I liked in them.

So, anything new to report on the floor?

Not yet. Will definitely update you when it happens. Will probably wait until our renovation downstairs is complete so the entire house isn't torn up at once. :-)

And thanks for all of your help @sammy and everyone else! This is a I wonderful thread. I cleaned it up a bit so the comments that weren't directly related to the solution--by me and a few other user--wouldn't distract from all the good information it has to offer.