In a wet room, the carpenter builds back walls, floor structure with fall and board backing that must meet wet room regulations before waterproofing and tiles are applied. Here are the wet zones, requirements for rigid and moisture-resistant substrate, fall to the drain and the interface between trades.
Introduction
A wet room — bathroom and utility room — is one of the most moisture-laden rooms in the house, and damage there is expensive and hidden. The carpenter's part lies beneath what is seen: back walls, floor structure with fall and the board substrate on which waterproofing and tiles are later applied. If the substrate is slack, moisture-sensitive or without fall, the subsequent sealing will not hold — no matter how good the tiling work is.
Wet room zones
A wet room is divided into zones based on how much water the surface is exposed to. The wet zone (around shower and bath) has the strictest requirements, while the rest, less loaded part of the room has more lenient requirements. The zones determine which materials and what sealing can be used where.
- 01Wet zone: the areas around the shower/bath that are directly sprayed — here the highest requirements are set for substrate and waterproofing.
- 02Other/wet zone: the rest of the room that is affected by moisture and steam but not direct water spray.
- 03The entire floor is considered wet: the floor must always be able to withstand water and slope to drainage.
The substrate must be stiff and moisture-resistant
Tiles and waterproofing cannot tolerate substrate movement — then the seal cracks and water penetrates. Therefore, a wet room substrate must be both rigid and moisture-resistant. Ordinary gypsum does not belong in the wet zone; approved, moisture-resistant wet room boards (e.g. cement-based boards) are used here on a frame set closer than a normal wall to provide the necessary rigidity.
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