I have an enclosed porch and I've just striped carpet and two layers of laminate as well as all the adhesive. I have it sanded down and the original tight-grain pine t/g floor looks amazing.

The porch is completely enclosed and surrounded with 17 single-pane glass windows. It has no heating or cooling. It is above a crawlspace that has free access to outside air. So it is protected from the elements but still gets large temperature and humidity swings. It also gets quite a bit of light from the windows, though we do have plenty of trees around.

I'm wondering what type of finish I should use on this floor. Just the same oil poly I use on indoor floors (probably Varathane floor finish)? Is there something more suited to these conditions? I have some Varathane spar urethane which says it is good for outdoor furniture and has UV protection, but it also says not to use in high traffic areas and I get the impression that means floors.

Should I plan to treat the bottom of porch? At some point someone put up fiberglass insulation but that's falling apart and not doing anything. I pondered about spray foam just to seal up the bottom and insulate it some.

Thanks!

 

Poly is not a great finish outdoors where the wood is subject to swings in the moisture content of the wood. So while you can use a floor poly, it may require some maintenence in the future if it blisters due to the moisture coming up from underneath. Pretty much any finish will be subject to that. But floor poly will wear the best.

 

Interior poly will probably be ok. I've used it on a bunch of wood porch ceilings and they held up well although we don't have quite the temperature swing you do further north. The main thin is it's not apt to get rained on.

 

I wonder if spar varnish would be an option. It's intended for coating the wooden parts of boats but I've never tried it on a floor.

 

I've tried spar varnish on oak door thresholds that were protected under a porch. It did not hold up very well at all.

 

Did the spar finish not hold up well because of the foot traffic? Or did the weather wreck it?

 

Foot traffic. Its under a porch, protected from the weather. Of course, peoples feet could be wet.

 

Spar varnish/poly dries to a softer finish than it's interior counterpart. That helps it withstand weather better, the hardness of interior poly helps it withstand traffic better.

 

There isn't a perfect product for this but polyurethane would be the best choice. Additionally, I really like the look of aged pine with two or three coats of oil based poly on it.