You can buy cedar kiln-dried and ready to use, or you can buy it green, sappy and heavy from a small mill or a neighbour with a chainsaw. Both boards can end up on the same bench, but only if the second one is seasoned first. Cedar has a reputation for being stable and rot-resistant, and mostly that reputation is earned. It still shrinks as it loses moisture, though. Plane a green board flat on Monday and there is a fair chance it will look like a propeller by the weekend. Seasoning is not complicated. It is patience, airflow and a tidy stack.
What Seasoning Actually Does
Green timber is full of water. Some of it sits in the cell cavities and drains away fairly quickly; the rest is bound inside the cell walls, and that is the part that causes trouble. As the bound water leaves, the wood shrinks. It shrinks far more around the growth rings than across them, which is why boards cup, bow and twist rather than simply getting smaller.
The ends of a board dry much faster than the middle, and that difference creates stress. If drying is too fast, the surface shrinks over a still-damp core and you get surface checking, end splits or a hard, brittle case that will not machine cleanly. Dry it too slowly, or in still, damp air, and you get mould and staining instead.
Cedar is a softwood with a fairly low density and good natural durability, so it moves less than oak or beech and resists fungal attack better than most. That makes it forgiving. It does not make it immune. Western Red Cedar, the type most commonly sold in the UK for cladding, gates and outdoor furniture, will still split along the grain if you force it dry against a radiator. Cedar of Lebanon and Japanese cedar behave in similar ways; treat the species name as a hint, not a guarantee.
Air-Drying Cedar Outdoors
Air-drying is the slow, cheap route and it suits cedar well. The aim is to keep air moving around every face of every board while shielding it from rain and direct sun.
Start with the ground. Lay a few sturdy bearers — old fence posts or lengths of treated timber — on a hard, dry surface, and set your stack on top. Never let boards sit directly on soil, concrete or grass; they will wick moisture up and stain. Pick a spot with open airflow, ideally with the prevailing wind running along the stack rather than into its end grain.
Allow roughly a year per 25mm of thickness as a working rule of thumb. A 50mm board might need two years. Cedar dries faster than that in a breezy summer, but the middle of a thick board takes its time, and there is no way to hurry it safely. Seal the ends of every board before you stack them. A brush-on end-grain wax or a couple of coats of exterior paint slows moisture loss at the ends and is the single cheapest way to reduce splitting.
Sticker Stacking, Step by Step
Stickers are the thin strips of dry wood that separate each layer. Get them right and the rest follows.
- Sort your boards. Group by thickness, and keep the best faces up. Remove bark and any obviously rotten edges; they attract mould and insects.
- Use dry stickers. Roughly 20–25mm square is plenty. They must be drier than the timber you are stacking, otherwise you are feeding moisture back in. Kiln-dried offcuts or dry softwood battens work fine. Avoid green or resinous strips.
- Space them evenly. Around 300–450mm apart along the length, with one right at each end so the board ends cannot curl.
- Line them up vertically. Every sticker should sit directly above the one in the layer below. Staggered stickers create pressure points and you will get ripples and bowing.
- Build up in layers. Keep layers level, and keep the same number of stickers in each row. Then weight the top with a few heavy boards or a couple of concrete blocks to hold everything flat.
- Cover, do not wrap. A sheet of corrugated metal or a weighted tarp over the top, overhanging the sides, keeps rain off while leaving the sides open. Never drape plastic down the sides — you are building a greenhouse, and mould will thank you for it.
Once a month, check the stack. Re-tighten the covering, look for mould or insect activity, and pull out a sample board to test.
Moisture Meters: What the Numbers Should Say
A moisture meter turns guesswork into a number, and decent ones are not expensive. Pin meters measure electrical resistance between two pins pushed into the wood; pinless meters read a small field just below the surface. Both have limits.
Take several readings, not one. Work along the board, at both ends and in the middle, and average them. Push the pins in along the grain rather than across it, and aim for about a quarter of the board's thickness so you are reading the core, not the dry shell. Where the meter has a species setting, use it. Let timber come to room temperature first, because cold wood reads wetter than it is.
As a rough guide, timber for interior use in a heated house should settle around 8–12% moisture content. For outdoor projects, gates, planters and cladding, 15–18% is a reasonable target — it will come close to the natural equilibrium of British weather anyway. Boards that read in the low twenties are still drying. Leave them alone.
Storage Rules That Prevent Splits, Mould and Warping
Seasoned timber is not finished with you. It will keep absorbing and releasing moisture for the rest of its life, so storage matters as much as drying.
- Keep it flat and supported. No leaning boards against a wall; they bow under their own weight within weeks.
- Get it off the floor. Bearers again, even in a workshop. Concrete floors are damp floors.
- Keep the stickers in place until the timber is genuinely acclimatised to where it will live.
- Store indoors for interior work. Move boards into the house or a dry workshop two to three weeks before you cut them, so they settle to that environment.
- Ventilate, then cover. Airflow in, rain and dust out. Avoid sealed plastic sheeting in unheated sheds.
- Watch the ends and the edges. Small splits at the ends are normal on any board; splits running up the middle of the face are not.
- Mind the dust. Cedar dust is a common irritant and repeated exposure can sensitise skin and airways. Use extraction or a suitable mask when you machine it, and if you react badly, stop and seek medical advice.
When Things Go Wrong
Shallow surface checks are cosmetic and generally harmless on outdoor timber. Trim the ends back if splits run deep enough to weaken a joint. A little white surface mould wipes off with a cloth and a weak bleach solution, but if the boards smell musty or the mould has gone black and fibrous, re-stack them with more airflow and drier stickers.
Warping means the timber dried too fast or was stacked badly; re-stack it with closer stickers and more weight, and give it more time. Case-hardened boards that move every time you plane them need longer in the stack, not more pressure from your hand plane.
Before You Cut: A Quick Checklist
Pick a straight board and take a meter reading in three places. Check it is flat across the width and along the length. Confirm it has had at least a fortnight in the space where the finished piece will live. If all three pass, start cutting. If any of them fail, put the board back on the stack and use a different one — an hour of patience now saves a ruined project later.
Photo: Alexander Walch / Pexels
