Porch deck finishing choices

[Wayne Whitney]

Hello,

I'm replacing the deck of my covered, open porch. The new deck is 5/4 x 4 redwood v-notch T&G. [Obviously solid boards with a gap would provide better drainage, but IMHO that is too informal for a covered porch.] A couple questions on finishing:

1) I do want to finish the redwood, as otherwise it will tend to get a bit grungy from foot traffic. My instinct is to use a penetrating oil finish, rather than a film finish, because when a film finish fails it will flake off and require sanding to remove it. I'm leaning towards Penofin red label. Anything I'm missing here?

2) Is it useful to prefinish the underside before installation? What about the tongue and groove? The porch deck is 3.5' - 4' above open soil, with the region underneath enclosed but vented.

Thanks, Wayne

[Lawrence]

Nope. If your preference is a penetrating finishes then thats fine. It will not be as durable or cleanable as a polyeurathane but it is indeed easier to apply and maintain. This is why poly is usually used indoors and penetrating oils mostly for outdoor porches.

Woodworking tradition is that the underneath not have finish. Just too much trouble and too little payoff. I have to say that it is useful since it further protects the boards and will reduce and expanding and contracting that occurs with all wood. Having said that, almost no one would go what is a significant amount of trouble to finish a surface that no one ever sees or uses.

[3G]

| > I'm replacing the deck of my covered, open porch. The new deck is

5/4 | > x 4 redwood v-notch T&G. [Obviously solid boards with a gap would | > provide better drainage, but IMHO that is too informal for a covered | > porch.] A couple questions on finishing: | >

| > 1) I do want to finish the redwood, as otherwise it will tend to get a | > bit grungy from foot traffic. My instinct is to use a penetrating | > oil finish, rather than a film finish, because when a film finish | > fails it will flake off and require sanding to remove it. I'm | > leaning towards Penofin red label. Anything I'm missing here?

Cabot Australian Timber oil is what I prefer.

| | Nope. If your preference is a penetrating finishes then thats fine. | It will not be as durable or cleanable as a polyeurathane but it is | indeed easier to apply and maintain. This is why poly is usually used | indoors and penetrating oils mostly for outdoor porches. | >

| > 2) Is it useful to prefinish the underside before installation? What | > about the tongue and groove? The porch deck is 3.5' - 4' above | > open soil, with the region underneath enclosed but vented. | | Woodworking tradition is that the underneath not have finish. Just | too much trouble and too little payoff. I have to say that it is | useful since it further protects the boards and will reduce and | expanding and contracting that occurs with all wood. Having said | that, almost no one would go what is a significant amount of trouble | to finish a surface that no one ever sees or uses. |

[Wayne Whitney]

Well, it's no more trouble than backpriming siding. Would it be silly to finish the back face without finishing the tongue and groove? Seems like it would still equalize water vapor absorption rates between faces to reduce cupping.

Cheers, Wayne

[Lawrence]

The job is yours.

[Lawrence]

That's true except siding is more likely to be backprimed since it is totally exposed to the elements and is actually your first barrier against rain and such. A porch floor has no such problem especially underneath.

IMHO is is silly to finish either the back side or the grooves. Just install the flooring and finish it in place, that's the way.

It could be damp under there so if you are worried about it then it definitely makes sense to use a vapor barrier between the finish floor and the joists or subfloor. Felt paper or paper especially for flooring are the usual products I see in this application. 6 mil poly is usually on hand as well. Heck, use both and it will still be less trouble than finishing the boards before they are installed. That's a total pain in the ass.

[Wayne Whitney]

I guess what I meant was, supposing I wish to go to the extra effort of finishing the backside, is that useful by itself, or is it only useful if I do all six faces?

This actually strikes me as a bad idea, as the floor deck should be able to exchange water vapor through both faces.

Right, those aren't vapor barriers.

Cheers, Wayne

[Lawrence]

Good luck and good bye.