ᐅ Renovation of an old basement bathroom with a damp exterior wall
Created on: 24 Oct 2025 08:22
D
DanSai81Hello everyone,
I have already asked this question in another forum but was advised to try here.
In our house (built in 1975), an existing bathroom in the basement is to be renovated. The bathroom includes a shower, toilet, and sink. The shower and toilet are located on an exterior wall.
I have now removed all tiles and fixtures. During this process, I noticed that the exterior wall is damp in the lower 50cm (20 inches). My cheap moisture meter for firewood showed a value just above 30%. The other walls showed no readings at all.
The original plan was to grind off the tile adhesive so that the walls could be retiled later. However, I am now concerned about the damp wall. In the damp area, the tile adhesive has come off much more easily than on the other walls.
Is my plan sufficient to prepare the wall by applying liquid waterproofing to the wall and floor area in the shower before tiling? Or do I need to use cement boards? I have read varying advice online. Some say to bond the cement boards directly to the wall, but the product data sheets all state that a substructure is necessary.
The previous tiles lasted 40 years; the bathroom was only used for a few years and was unheated. The new bathroom will have heating and will be used regularly.
We once had an expert inspect the basement walls. At that time, he said it was not a problem and that only external waterproofing could help. He recommended simply heating and ventilating the rooms. There are two laundry rooms adjacent to the bathroom.
I would appreciate any concrete advice or information. The bathroom is currently being prepared for a caregiver who looks after my parents-in-law at home.
Many thanks and best regards,
Daniel
PS: There are no efflorescence deposits, the rooms do not smell musty, and the previous wall covering is still intact.
I have already asked this question in another forum but was advised to try here.
In our house (built in 1975), an existing bathroom in the basement is to be renovated. The bathroom includes a shower, toilet, and sink. The shower and toilet are located on an exterior wall.
I have now removed all tiles and fixtures. During this process, I noticed that the exterior wall is damp in the lower 50cm (20 inches). My cheap moisture meter for firewood showed a value just above 30%. The other walls showed no readings at all.
The original plan was to grind off the tile adhesive so that the walls could be retiled later. However, I am now concerned about the damp wall. In the damp area, the tile adhesive has come off much more easily than on the other walls.
Is my plan sufficient to prepare the wall by applying liquid waterproofing to the wall and floor area in the shower before tiling? Or do I need to use cement boards? I have read varying advice online. Some say to bond the cement boards directly to the wall, but the product data sheets all state that a substructure is necessary.
The previous tiles lasted 40 years; the bathroom was only used for a few years and was unheated. The new bathroom will have heating and will be used regularly.
We once had an expert inspect the basement walls. At that time, he said it was not a problem and that only external waterproofing could help. He recommended simply heating and ventilating the rooms. There are two laundry rooms adjacent to the bathroom.
I would appreciate any concrete advice or information. The bathroom is currently being prepared for a caregiver who looks after my parents-in-law at home.
Many thanks and best regards,
Daniel
PS: There are no efflorescence deposits, the rooms do not smell musty, and the previous wall covering is still intact.
Similar topics