Redwood deck: what sort of sealant/stain should I use (if any)?

June 18, 2018 11:24 AM

I recently had my front porch and steps cleaned up, sealed, and covered with low- to mid-grade redwood decking ("construction grade"). What's the best way to decide which sealant and possibly stain to use on the redwood boards?

It's been 2 months, and I'm ready to pressure wash and seal the deck, but I have zero experience with stains, sealants, etc. (I do have a fair amount of experience painting interiors, but mostly execution, not picking product.)

My first priority would be non-toxicity, in terms of off-gassing (??) or environmental impact (I don't know much about it). My second priority would be effectiveness in sealing vs. sun and rain (south facing porch). My third priority would be aesthetics/appearance.

(I also have railings and posts to seal/stain.)

I gladly welcome any expert advice or personal experience or random comments.

If there are any wonderful online guides out there with solid, vetted info (again, I have no clue), please pass them along. Thanks!

posted by mrgrimm to Home & Garden (5 answers total)

I don't have any decking, but I find my independent Benjamin Moore Paint Store (and likely Sherwin Williams) to be the perfect place to get this sort of question answered - and to purchase the product. Yes, it will likely be more expensive than a big box store, but IMO, you get what you pay for in terms of paint and stain.
posted by sarajane at 12:20 PM on June 18, 2018 [1 favorite]

Though your third priority, one of the decisions you need to make is solid stain (basically like a paint, little grain will show if any), semi-transparent stain (some color, brings out the grain, what I'd most likely use for redwood), and clear stain (will most likely still allow the wood to grey, but will waterproof). My next thought then would be how often are you willing to re-treat? Clear will probably be an annual event, tbh. Semi-transparent, depending on the brand, will need it before three years, and then a solid stain is a three year event (maybe longer, depending).

SaraJane is correct - I'd send you to a specialty store (or a small hardware store) over a big box - knowing that the big box stores don't necessarily carry the best, they carry what suppliers they've negotiated singular agreements with during that time period. (I.E. Olympic is no longer available at Lowes due to Sherwin Williams distribution agreement, so if you want Olympic or affiliated you'll need to go to Home Depot.)

*Disclaimer: I am a paint librarian, but not your paint librarian.
posted by librarianamy at 12:39 PM on June 18, 2018 [1 favorite]

I've used Penofin Marine oil and Red Label both are great, but expensive.
posted by Dr. Twist at 3:22 PM on June 18, 2018 [1 favorite]

My first priority would be non-toxicity, in terms of off-gassing (??) or environmental impact (I don't know much about it). My second priority would be effectiveness in sealing vs. sun and rain (south facing porch). My third priority would be aesthetics/appearance.

Raw linseed oil is super cheap and fits those criteria. It will take anywhere from a few days to a few weeks to stop making the soles of your feet oily when you walk on the deck, though, depending how much direct sunlight it's exposed to (ultraviolet light helps it oxidise and cure). It doesn't actually seal wood like a varnish would do, but it soaks in and makes it water-repelling, then oxidises and hardens both on the surface and deep inside the wood's pores.

Simple oil finishes degrade with weathering, but because quite a lot of the oil ends up inside the wood where light can't penetrate much, it keeps on protecting it to some extent even when it looks well overdue for a re-do; and a re-do is as simple as a wash-down and re-oil because you don't need to sand off a flaky old finish.

Commercial "boiled" linseed oil sets faster but that's because it has some additives to help it oxidise, and those additives are poisonous. You can also take your life in your hands and heat-treat it yourself to reduce curing time without turning it toxic, but this is hella dangerous; a litre of oil at 450°F is not something you want to be anywhere near if it suddenly bursts into flame.

I always just use the raw stuff, and keep a large cotton bathmat between any recently oiled bit of decking and the inside of the house until the bathmat stops showing new oily footprints. As a bonus, it feels really nice to walk on barefoot, and any linseed oil the soles of your feet pick up if you walk on an oily deck in bare feet is as good for your skin as it is for your deck.
posted by flabdablet at 5:39 AM on June 19, 2018 [2 favorites]

Seconding the Penofen, especially the red label. It’s expensive, but a gallon goes a long way.
posted by donguanella at 4:49 AM on June 23, 2018