Sauna flue installation

What a sauna flue consists of

• The first section above the stove: a heat-resistant single-wall pipe, sometimes surrounded by a stone basket or a water tank. This is the hottest section.
• The transition to an insulated twin-wall flue below the ceiling. From this point to the cap the flue is insulated.
• The ceiling passage: a non-combustible box with insulation, through which the flue crosses the timber ceiling and the vapour barrier.
• The attic and roof section with a roof passage, fixing and cap.

We do not run a single-wall pipe all the way to the roof: in the attic it cools down, tar condenses on its walls, and the hot pipe is too close to the timber. The stove manufacturer specifies the outlet diameter and how long an uninsulated section may be used.

Distances to timber and the floor by the stove

In a sauna the most important thing is the distance from the flue to the timber walls and ceiling. If the system manufacturer states a distance in millimetres, we keep to it; if not, the distances in the regulations apply. A heat shield on the wall by the stove can reduce the distance only if the stove or flue manufacturer allows it. A timber floor in front of the firebox must be covered with non-combustible material.

How sauna flue installation is done

1. Stove data We check the stove outlet, the diameter and the manufacturer's instructions: distances, the type of first section and whether the stove can carry the weight of the flue.
2. Route through the ceiling We set the point where the flue will cross the ceiling and roof so it misses the beams and comes out in the right place in relation to the ridge.
3. First section We install the heat-resistant section above the stove and the transition to the insulated flue.
4. Passage We cut the opening in the ceiling, fit the passage box, fill it with non-combustible insulation and seal it airtight to the vapour barrier.
5. Roof and cap We take the flue out through the roof, fix it and fit the cap. The height depends on the distance to the ridge.
6. First firing We check the draught and that the timber by the passage does not overheat.

A sauna in a separate building

A garden sauna is often low, with a shallow-pitched roof, and under the building code the flue turns out longer than the sauna itself. If the flue is too short, the draught is weak, the stove smokes when the door is opened, and sparks land on the roof. A spark arrester is not mandatory, but if the sauna is close to trees or neighbouring buildings, it is worth considering.

A sauna flue is cleaned twice a season, because a sauna stove is a long-burn appliance. So when installing it we plan how it will be reached: through the stove, a cleaning door or from the roof. More on cleaning: sauna stove cleaning.

How much does sauna flue installation cost?

There is no single price. It depends on the flue length from the stove to the cap, the type of ceiling and roof passages, the roof pitch and covering, whether the first section needs a stone basket or water tank, and access. Materials are priced separately. In the form, give the stove model, the sauna height and the roof type, and the specialist will name the price before the work. Other prices: prices.