Paint or stain as a type of vapour barrier.

[Big Builder]

I am having a humidity problem in my crawlspace and had a thought that
I could spray the underside of joists and subfloor with my airless to act as
a barrier to moisture that is affecting my hardwood upstairs. Does anyone have any ideas about what the best product would be?

[tooltroll]

A couple good coats of alkyd primer/sealer should do the trick nicely. Cover every square millimeter you can.

[Big Builder]

Thanks Bob,

Do you think there could be any ill effects to the floor from absorbtion through the subfloor to the bottom of the hardwood??

[tooltroll]

It's pretty likely, yeah. All depends on your crawlspace conditions. . . I've only got a little crawlspace under an addition, and it's pretty nasty in there. Haven't gotten to that part yet. . . sigh. . .

[Big Builder]

That is my one concern with spraying. I don't want to make the condition of the floor worse. I will try a small area and let you know.

The conditions in the crawlspace are not bad. It's bald rock and between 3 and 4 feet high. Very dry except one corner where waster sneak under the footers.

Any ideas on a good low vapour primer?

Have to keep the few brain cells I have. Even with a respirator I find these space spaces still get toxic.

[tooltroll]

Sorry- In general, moisture can creep through subfloor from crawlspace. I don't think an alkyd primer will cause any problems, since there ain't water in it. As far as fumes go, best ask at the store for low vapour stuff, and use a couple of fans to ventilate the space while you're spraying, if you can- one blowing in at one end, the other one pointing out at the other end. Save the brain cells - Collect the whole set! :)