Should I use thompson semi-transparent watersealer underneath a pressure-treated wood deck?

Question

The boards are screwed in from the underneath of the deck.

Answer 1

I agree with thompsons being the worst. CWF (clear wood finish) made by flood is the best I have found.

Answer 2

If you can afford it, it can't hurt. I would.

Answer 3

Thompsons water seal is the WORST possible deck treatment you can use...Go get some Cuprinol from Sherwin Williams..

Answer 4

the more sealer the better even apply it to the preassure treated stuff it will only help

Answer 5

As a painter since the 1970's I can truly say that Thompsons is really bad sealer.

It is not necessary to seal the underside. The wood needs to breath.

Answer 6

actually I wouldnt put it under a deck

Wood needs to breath and the underside is a good place not to put the sealer so the wood can do what nature made it to do

Just like you dont paint both sides of the siding on your house

But thats my opinion