Fresh-sawn, antiseptic or pressure-treated timber?
Choose fresh-sawn timber for structures that will stay dry or are temporary, antiseptic-treated timber for roofs and frames sheltered from direct rain, and pressure-treated timber for anything in constant moisture or ground contact. The higher the moisture risk, the deeper the protection needs to be. We saw all three ourselves at our own mill in Latvia from pine and spruce, in the same sizes, from 25x50 to 400x400 mm.
The three options in brief
Fresh-sawn boards and beams
Untreated softwood with natural moisture straight after sawing: fresh-sawn boards and beams.
- Pros: the most economical option, easy to work, no chemical treatment; you can paint, oil or treat it later as you wish.
- Cons: left damp without protection it can develop blue stain and mould; it shrinks a little as it dries, so stack it with spacers in a ventilated place before finishing.
Antiseptic-treated boards and beams
The antiseptic protects the surface layer against fungi, rot, blue stain and wood-boring insects: antiseptic-treated boards and beams.
- Pros: lasts longer than untreated wood; a frame copes better with the weather before the roof is on; costs only a little more than fresh-sawn.
- Cons: protection is in the surface layer only, so it is not meant for ground contact or constant moisture; cut ends need extra treatment.
Pressure-treated (impregnated)
The timber goes into an autoclave, a vacuum draws the air out of the cells and pressure forces the preservative deep into the wood: pressure-treated boards and beams.
- Pros: protection goes beyond the surface, so it suits ground contact and long-term moisture; the longest service life outdoors.
- Cons: the most expensive of the three; cuts and drill holes need treating with preservative; offcuts must not be burned in a stove or fireplace, and it is not meant for sauna benches or food-contact surfaces.
Which one where: table
| Use | Recommended | Why |
|---|---|---|
| Wall and partition framing in a dry room | Fresh-sawn or antiseptic | Low moisture risk, the wood needs to dry |
| Rafters, battens, counter-battens | Antiseptic | Under the roof, but condensation and leaks are possible |
| Floor beams, joists over a ventilated crawl space | Antiseptic | Dry, but cool and hard to inspect |
| Carport, shed, log store | Antiseptic | Outdoors but sheltered from direct rain |
| Deck substructure, joists | Pressure-treated | Long-term moisture, water collects under the boards |
| Fence posts, ground contact | Pressure-treated | Constant moisture and soil fungi |
| Jetties, footbridges, raised bed edging | Pressure-treated | Direct contact with water and soil |
| Concrete formwork, scaffolding, temporary builds | Fresh-sawn | Short-term use, price matters |
How to choose: three questions
- Will the wood touch soil, concrete or water? Then pressure-treated only.
- Is it under a roof but outdoors or unheated? Go for antiseptic-treated.
- Will it be in a dry room or used only temporarily? Fresh-sawn is enough.
If in doubt, take the next level of protection: the price difference is usually smaller than replacing the structure later. For ready outdoor solutions see also decking boards and fence boards.
Price and ordering in Riga
Antiseptic treatment and impregnation are already included in the price per m³. The current price per m³ and per piece is shown instantly in the calculator on each product page, with VAT for private buyers and without VAT for companies. For the treatment class and batch details of pressure-treated timber, call +371 29568256. Minimum order is 1 m³, the PDF invoice arrives by e-mail at once, and we deliver with our own truck in Riga and the surrounding area (delivery) or you collect free of charge from Vējstūru iela 3. All types are in sawn timber.
FAQ
Can antiseptic-treated timber go in the ground?
No, for ground contact choose pressure-treated timber.
What is the difference between antiseptic and pressure treatment?
Antiseptic protects the surface layer; with pressure treatment the preservative penetrates deep into the wood.
Can I treat fresh-sawn timber myself?
Yes, with a brush or sprayer, but that is a surface treatment and does not replace pressure impregnation.
Can pressure-treated wood be used in a sauna?
For benches and anything in contact with skin choose untreated wood, such as our aspen bench boards.
Can I burn pressure-treated offcuts?
No, chemically treated wood should not be burned in a home stove. For heating choose split firewood.