Thermo Spruce Cladding Board – Triple Slatted Profile – 140×26 mm – 4500 mm (15 ft.)

Thermo Spruce Cladding Board

Thermo Spruce gives you a spruce cladding board made more stable by heat rather than chemicals, machined to a triple slatted face that turns a plain wall into fine, even lines. Each board is 140×26 mm and 4500 mm long, a solid section that feels substantial on the wall yet still cuts and fixes easily. Use it on sauna walls, relaxation rooms and feature walls, or on garden buildings and exterior elevations. Every board is stocked in our warehouse for delivery across Ireland.

Why Thermo Spruce?

Thermal modification heats the timber in a low oxygen kiln. That permanently changes the cell structure of the wood, so it takes up far less moisture than untreated spruce and moves less as the air around it warms, cools, wets and dries. For you, that means boards that stay straighter on the wall, joints that stay tighter, and a wall that holds its lines through the heat and humidity of a sauna or the swings of an Irish year outdoors.

The heat also gives the spruce a warmer tone than a pale, untreated board, with the grain and knots still visible, so the wall has more character than a uniform modern profile. The triple slatted profile machines three slats into the face of every board. Up close it reads as a lined texture with soft shadows; from across a room or a garden it gives a clean, linear finish that suits a traditional sauna as well as a contemporary garden room.

Installation guidance

Spruce is one of the easiest timbers to fit, and the heat treatment does not change that. Fix the boards onto a level batten frame with a ventilated cavity behind, so air can move behind the wall and any moisture dries out. Use stainless steel fixings, which will not stain the timber or corrode in a humid room.

One honest point: thermally modified timber is a little more brittle than untreated wood, so pre-drill close to board ends and keep fixings back from the edges. Set the first board out dead level and run the slats the same way across the whole wall, because the fine lines of the profile make any drift easy to spot.

Finishing & maintenance

Inside a sauna the rule is simple: leave the timber bare. Never use oil, varnish, paint or exterior stain in a hot room, as they can turn sticky, blister and give off fumes when the room heats. Let the room ventilate after each session so the boards dry fully, and wipe the walls down from time to time with a damp cloth and a little mild soap. If you want extra protection on the walls and ceiling, use our Saunawood Protection Wax, which is made for saunas, and keep it off the benches.

Outdoors you have two good routes. Left untreated, the boards weather to a silver grey within the first year or two, a soft, even look many people choose on purpose. To keep the warm tone, apply a UV protective oil made for thermally modified timber within the first few months, refresh it every year for the first couple of years, then every two or three years. Most people oil it to keep the colour. Avoid film forming paints and varnishes outdoors too, as they tend to crack and flake. Whichever route you take, a soft brush and clean water once a year keeps the wall looking sharp.

See every length in our Thermo Spruce sauna cladding range.