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Material to protect newly refinished hardwood floor?

1K views 2 replies 2 participants last post by  gilliganslin 
#1 ·
I am almost done re-finishing the hardwood floors in my old (1906) home. There is no sub-floor; this hardwood (Douglas Fir) sits directly on top of the floor joists. The hardwood floors will have 4 coats of oil-based polyurethane.

In the crawlspace, insulation sits beneath the floor in between the floor joists. I've heard I should put a breathable barrier on the bottom side of these floor joists to protect the newly re-finished floor.

Is this true? If so, what material should I use (tyvek?)

Thanks.
 
#2 · (Edited)
Douglas fir is not a hardwood although it can seem harder as it ages. If it has lasted this long with just the insulation (which should have its own moisture barrier) I would leave it alone so it can breathe and respond to temp changes. A moisture barrier between the joists and the finish floor and the joist tops might have been an idea for consideration but the floor has worked out since 1906?

I think you risk more problems sealing the bottom of your floor joists, especially in a Bay Area climate. As you know, you can really wish for a sweater in July and August in your part of the World if near the Bay as it can be cold on foggy mornings or evenings. In the armpit of the Bay we had fairly dramatic drops in temps overnight most of the summer months.

I worked on exterior projects in Foster City where you had to watch a tide chart when building decks or installing pools or you would hit sea water drilling or digging. A friend dated his future wife based on a tide chart because she could not open her exterior apartment doors at high tide. Floors must have had to flex a lot too! My own custom home, at the base of the East Foothils in San Jose, was nicely custom built but still rattled and rolled at times and it had only a crawl space for a foundation. I put bamboo floors in it to deal with the temp and humidity changes on a daily basis.

I would check to make sure you have adequate crawl space/foundation vents though. There was a trend to close them off out your way which was a bad move. It is good to check them once in awhile to make sure they are intact or you could end up with unwanted tenants. Let your crawlspace breathe! I assume water is not draining into it and it smells like healthy dirt when crawling around under the house? Then let it be.
 
#3 ·
Thanks for the helpful reply, sdsester. (I used hardwood in lay terms.)

We purchased this home last year (June 2012) and have done a whole home remodel (down to the studs). Funny you mention about the trend in closing vents. The previous owner did so but also left a couple open... Lo and behold, we found after closing escrow that we bought an Animal Farm - we ended up with 7 raccoons and a few old rat nests. I think you replied to some of my posts helping me out dealing with the raccoons...

In any case, why we acquired the home last summer, there wasn't any insulation in the crawlspace below the 1st floor, nor was there any polyurethane. The owners merely painted the floors... (That was a bundle of fun stripping that paint off.) As part of our remodel, we put in new vents and rat proofed the crawlspace (yes, it did smell before when it was just dirt.) It smells just fine now.

Given the above, please let me know if you think I should install a breathable membrane below the floor joists.
 
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