Varnish on the bottom of wood flooring?

Woodshop
#1

I was talking to one of my co-workers today, and they mentioned they were putting down some hardwood flooring in their home. And they mentioned what a pain it was putting on the varnish before laying the floor down. I asked what they meant, and they said that they learned from there father back in the day that it helps the floor if you put a layer of varnish on the bottom of it, in addition to the underlayment, to help against moisture. I’ve never heard of this, and I was wondering if anybody else at DMS had, and what y’alls’ thoughts on it were?

#2

I put traditional tongue and groove #2 oak in most of our house 15-20 years ago. I hadnt heard of varnishing the bottom. I havent had any issues with cupping, I sanded and finished the floor. I still have a manual floor nailer you are welcome to borrow. It was alot of work, first project was two small bedrooms which ended up being harder than living/dining floor and family room due to the number of closets and doors and a hallway.

#3

I’ve done wood flooring before, as has my father, and his father too. And we’ve never had any issues with that either. But I never claimed that I know everything, and it’s always good to hear New perspectives. So just reaching out to the larger community to see if anyone else had any thoughts on that, or ever heard of the practice.

#4

Any chance your coworker’s father was working with wood flooring that did not have backside relief cuts? I think, maybe, the use of boards flat of both sides would be more troublesome and therefore benefit from backside protection. Same applies to really wide planks as well.

#5

I’ll ask him tomorrow

#6

You want a vapor barrier under your wood flooring. Normally this is accomplished by the Wood Flooring Urethane. If you are not using urethane then maybe they are accomplishing this with varnish. There are other vapor barrier techniques for concreate floors so not sure why they would use varnish.

I will like to say that I think Wood Flooring Adhesive is the way to go. Feels way more solid and give you peace of mind for water and cracks.

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