What wood to withstand rain?

[radhak]

A friend has a gable house, with a circular 'window' high up on an external wall - more ornamental than utilitarian (leads into an attic). It used to have a slats installed, cut such that water would not get in. Couple of years ago he asked my help in replacing the slats as they had rotted away, being directly exposed to rain. (The slats are simply nailed in).

I did the job quick, but made a blunder : I did not stop to think deeper about the wood, and used regular poplar. Well, today he tells me that what we put up has rotted again, and needs replacing.

The job itself is pretty easy, but what can I do to avoid the wood rotting in the rain in a couple of years? Exterior wood? Regular wood with exterior paint? Exterior wood with exterior paint? Or some sort of artificial material?

[LCHIEN]

if you want natural wood look, Cedar, redwood, cypress, teak or ipe are all naturally rot resistant with no finish, but they will weather and look weathered (turn a silvery gray) and ultimately can rot away but it will take years. Cedar is probably the easiest to find. You can also finish them with UV resistant varnish coatings every few years and they will last longer and look "natural" - no graying or splintering from weathering.

Pine, poplar etc can be painted but the paint will need to be renewed every few years but properly paint protected can last a long time. Louvers would make painting harder to coat all the sides that are exposed - even if not directly rained on or sunned upon they will see moisture and humidity and ultimately need repainting.

There are wood substitutes made of plastic that will last a long time without rotting, paint would still have to be replaced when it starts fading or peeling. One popular brand goes by the name TREX; look in the decking dept of Lowes or HD.

[Knottscott]

White oak, lyptus, and mahogany are a couple of other good exterior woods. Cedar is pretty readily available around here, but YMMV.

[JimD]

Pressure treated pine will take paint well when it is dry. Painted, it would last indefinitely.

Jim

[cabinetman]

Your longest lasting protective finish would be a painted finish. If a woodgrain needs to be seen, a penetrating oil like Penofin Red Label will provide suitable protection, which would be an easier finish to maintain than a film finish (like a spar varnish, or spar urethane), which would be a PITA to sand and recoat.


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[chopnhack]

https://www.azek.com

expensive but final

[Bruce Cohen]

TREX,
And you only have to deal with a mop and soapy water.

Bruce