Sauna Wood

If you are building a sauna, or re-lining one that has gone grey, the wood is the decision that shows. It is also the one people get wrong — usually by buying ordinary cedar from a lumberyard, which is kiln-dried for a deck and not for a room that runs at 190°F.

This is sauna-grade lumber from PROSAUNAS: 63 milled profiles across seven species, in stock lengths from 2 to 14 feet. Cladding for the walls and ceiling, thicker stock for the benches, and matching trim to finish the corners. Boards run $2.67 to $176.31 each depending on species, profile and length — $1.33 to $29.38 per linear foot.

Not sure which species? Tell me the two or three you are deciding between and I will mail you samples, free. Grain and colour do not photograph honestly, and this costs you nothing.

Shipping is free on wood orders over $999. More on delivery below — the long boards have one real constraint worth knowing before you order.

Which wood goes where

Cladding lines the walls and the ceiling. It is tongue-and-groove, so the boards lock together and the face stays flat as the wood moves through each heat cycle. The V-joint and nickel-gap profiles leave a deliberate shadow line between boards; a plain T&G reads as one continuous surface.

Bench material is thicker stock, milled smooth on four sides with eased edges so there is no sharp corner anywhere a bather sits. This is the one place the species choice is not cosmetic — see below.

Trim and moulding finishes it: corners, door casings, and the T-moulding that covers a joint between two runs of cladding. Same species, same mill, so it actually matches instead of nearly matching.

The seven species, and how to choose

Western Red Cedar — the classic, and the one most people picture. Dimensionally stable, naturally resistant to decay and warping, warm reddish tone, and an aroma that comes forward as the room heats. The vertical-grain clear A+ stock is knot-free. It is also the most expensive thing on this page.

Nordic Spruce — the traditional Finnish wall material and the least expensive cladding I carry. Pale, lightly knotted, and perfectly good for walls and ceilings when the budget matters more than a flawless clear face.

Hemlock — pale, even-toned and almost odourless. The usual answer for someone sensitive to cedar's scent, or who wants the room to disappear behind the heat rather than announce itself.

Aspen — pale, very smooth, completely odourless, and it stays notably cool to the touch at sauna temperature. That last point is why it is the default for benches and backrests.

Alder — reads warmer than aspen, a soft reddish-brown that deepens with use, with the same low thermal conductivity that makes a bench comfortable at full heat. Close-grained, takes a very smooth finish.

Thermo-Treated Aspen and Thermo-Treated Spruce — ordinary aspen and spruce taken through a high-heat kiln that drives out moisture and resin. They come out darker, honey to light brown, more dimensionally stable, and far less inclined to move with the humidity swings a working sauna puts them through. The aspen is still odourless and still cool to sit on; the spruce is a good deal cheaper than the aspen.

If you want one rule: cedar or spruce on the walls for looks and budget respectively, a low-conductivity species — aspen, thermo-aspen or alder — on anything you sit on. A cedar bench is beautiful and hotter than an aspen one. Behind a salt wall, use a thermally-treated species.

How much to order

Two numbers catch everyone out.

Coverage, not width. Divide your wall by the coverage figure on each product page, not by the board's actual width. A board that measures 3.72 inches covers 3.52 once the tongue is seated in the groove, and that five percent compounds across a room.

Add ten percent. Fifteen if you are running the boards diagonally or the room has more than one opening. Do not subtract the door from your square footage — the offcuts around an opening are rarely reusable.

Then order the longest lengths your walls will take. Fewer end joints looks better and goes up faster.

Or send me the room dimensions and I will do the take-off. Wall sizes, ceiling height, where the door and any window sit, and what you want on the benches. It takes me five minutes and it is the cheapest mistake in this whole project to avoid.

Delivery

Shipping is free to the continental US on wood orders over $999. Below that there is a $195 freight contribution, because a pallet costs the same to move whether it carries ten boards or a hundred.

Up to 40 boards at 8 ft or under generally goes FedEx Ground. Bigger orders, and anything over 8 ft, ship LTL freight on a custom skid.

The constraint worth knowing before you order: boards over 8 ft cannot take a liftgate. They need a dock, machinery, or hands at the site. If that is a problem, tell me and we will look at whether shorter lengths work for your walls instead.

Somebody has to be there to receive it, check the count and condition, and sign. Photograph anything that looks wrong before you sign — that is what makes a freight claim stick. Then let the wood sit in the room for a few days before you install it.

Frequently Asked Questions

Can I just use regular cedar from a lumberyard?
You can, and it is the most common expensive mistake in a DIY sauna. Construction-grade cedar is kiln-dried to a moisture content meant for a deck, often has knots that bleed sap at 190°F, and is not milled to a tongue-and-groove profile that tolerates the movement. Sauna-grade stock is dried further, graded clear, and profiled for the job. The difference shows in year two, not week one.

Which wood should I use for the benches?
A low-conductivity species: aspen, thermo-treated aspen, or alder. All three stay comfortable to sit on at full heat. Cedar benches look wonderful and get hot — so do hemlock and spruce. If you want cedar walls and a bench you can sit on in a hot room without a towel, mix them. Nobody will notice; you will.

How much wood does a sauna take?
A 5 x 7 foot room with a 7 foot ceiling works out at roughly 200 square feet of cladding once you count the ceiling, plus bench stock and trim. That is arithmetic on a bare box, not a quote — send me the dimensions and I will give you the real list, including the ten percent for cuts.

What is thermo-treated wood, and is it worth the money?
It is the same wood taken through a high-heat kiln that drives out moisture and resin. It comes out darker and markedly more stable, which is exactly what you want in a room that swings from dry and cold to hot and humid several times a week. It is worth it on a bench, behind a salt feature, and in any sauna that gets heavy use. Thermo-spruce is the inexpensive way to get the stability.

Can I get a sample before I commit?
Yes, free. Tell me the species you are choosing between and I will put pieces of the actual stock in the mail. Wood colour is the one thing a screen cannot show you honestly, and I would much rather you held it first.

Do you sell it by the board or by the square foot?
By the board. Each product page lists every profile that species is milled in and every stock length it is cut to, with a per-linear-foot figure so you can compare profiles fairly. Pick the profile, pick the length, add the quantity.

What finish should I put on it?
On the walls and ceiling, nothing. Bare wood breathes and that is the point. On benches and backrests, a paraffin-based sauna oil is the only thing that belongs in a hot room — never a varnish, a polyurethane or a deck stain, all of which trap moisture and will blister.

Do you ship to Alaska, Hawaii or Canada?
Not through the website — the freight on long lumber to those destinations has to be quoted individually. Email me with what you want and where it is going and I will get you a real number.