Hello everyone,
Our foundation slab is complete, the interior walls are almost finished, and preparations are underway for the hollow core wall elements.
The construction follows the “white tank” method. Included in the general contractor’s scope:
The foundation slab is made of reinforced concrete with a minimum thickness of 25 cm (10 inches), designed according to structural calculations, using water-resistant concrete (WU concrete) of quality C 25/30. On top of the slab, additional waterproofing against ground moisture and non-pressing seepage water is applied according to DIN 18195, using a bituminous membrane or an equivalent product chosen by the contractor. The basement exterior walls consist of double wall elements. These walls are made of two-layer precast concrete elements of quality C 25/30, with an overall thickness as per the drawings (minimum 25 cm (10 inches)), reinforced according to structural calculations following DIN 1045. The cavities between the two layers are cast on-site with waterproof concrete (WU concrete) of quality C 25/30, creating a seamless concrete core. The joints between the individual wall elements, as well as the transitions from the foundation slab to the walls, are sealed with joint tapes or suitable sealing elements (manufacturers Mastertec or Pentaflex). The exterior walls receive perimeter insulation made of XPS rigid foam boards, with thickness determined according to the KfW 55 standard calculation.
Currently, part of the basement is heated and separated from the unheated basement by a 30 cm (12 inches) thick Poroton wall.
The heated part of the basement contains the utility room, a shower bathroom, and a guest room that is occupied 1 to 2 times a year for about two weeks each time. The ceiling height is 2.20 m (7 ft 3 in).
The basement is not classified as living space. Therefore, our general contractor believes that a vapor barrier (bituminous coating or similar) is not necessary.
There are many opinions on this topic online. Even my building supervisor is uncertain.
What do you recommend? Should I additionally apply a bituminous coating to the basement wall surfaces?
Or is it better to use a sealing plaster?
Is this something a homeowner can do themselves? I don’t know how to apply plaster, but I can paint.
A waterproofing company told me that in my case a bituminous coating would be sufficient since it is only about the vapor barrier. They would charge 19 € per square meter, which would come to about 1615 € for 85 m².
If I buy the material myself (e.g., Webertec 901), it would cost around 150–200 € for materials.
What do you think?
Our foundation slab is complete, the interior walls are almost finished, and preparations are underway for the hollow core wall elements.
The construction follows the “white tank” method. Included in the general contractor’s scope:
The foundation slab is made of reinforced concrete with a minimum thickness of 25 cm (10 inches), designed according to structural calculations, using water-resistant concrete (WU concrete) of quality C 25/30. On top of the slab, additional waterproofing against ground moisture and non-pressing seepage water is applied according to DIN 18195, using a bituminous membrane or an equivalent product chosen by the contractor. The basement exterior walls consist of double wall elements. These walls are made of two-layer precast concrete elements of quality C 25/30, with an overall thickness as per the drawings (minimum 25 cm (10 inches)), reinforced according to structural calculations following DIN 1045. The cavities between the two layers are cast on-site with waterproof concrete (WU concrete) of quality C 25/30, creating a seamless concrete core. The joints between the individual wall elements, as well as the transitions from the foundation slab to the walls, are sealed with joint tapes or suitable sealing elements (manufacturers Mastertec or Pentaflex). The exterior walls receive perimeter insulation made of XPS rigid foam boards, with thickness determined according to the KfW 55 standard calculation.
Currently, part of the basement is heated and separated from the unheated basement by a 30 cm (12 inches) thick Poroton wall.
The heated part of the basement contains the utility room, a shower bathroom, and a guest room that is occupied 1 to 2 times a year for about two weeks each time. The ceiling height is 2.20 m (7 ft 3 in).
The basement is not classified as living space. Therefore, our general contractor believes that a vapor barrier (bituminous coating or similar) is not necessary.
There are many opinions on this topic online. Even my building supervisor is uncertain.
What do you recommend? Should I additionally apply a bituminous coating to the basement wall surfaces?
Or is it better to use a sealing plaster?
Is this something a homeowner can do themselves? I don’t know how to apply plaster, but I can paint.
A waterproofing company told me that in my case a bituminous coating would be sufficient since it is only about the vapor barrier. They would charge 19 € per square meter, which would come to about 1615 € for 85 m².
If I buy the material myself (e.g., Webertec 901), it would cost around 150–200 € for materials.
What do you think?
B
Bauexperte5 Jul 2016 11:24I believe that your general contractor (GC) is responsible for ensuring proper execution. Even if you are misleading the building authority regarding the living area, your GC is definitely aware of what they are supposed to build.
Bauexperte
Bauexperte
B
Bauexperte6 Jul 2016 10:51cumpa schrieb:
No one is cheating anyone here. And what else does your statement in post #1 imply, other than that the living area size in your building project was somewhat adjusted?
cumpa schrieb:
The heated part of the basement contains the utility room, a shower bathroom, and a guest bedroom that is occupied 1 to 2 times a year for about two weeks each time. Ceiling height is 2.20 m (7 ft 3 in).
The basement is not designated as living space. Regards, Bauexperte
Was the waterproofing done correctly?:
The concrete slab and all joints were primed with undiluted bitumen primer applied with a roller, instead of a 1:10 dilution with water. After a drying time of about 1-2 hours, the transition from the slab to the walls and the joints were filled with fabric and thick-layer coating.
I am concerned about the undiluted primer. According to the consultant, it should not be a problem. However, another waterproofing company said it could be problematic because undiluted primer adheres poorly to waterproof concrete.
The concrete slab and all joints were primed with undiluted bitumen primer applied with a roller, instead of a 1:10 dilution with water. After a drying time of about 1-2 hours, the transition from the slab to the walls and the joints were filled with fabric and thick-layer coating.
I am concerned about the undiluted primer. According to the consultant, it should not be a problem. However, another waterproofing company said it could be problematic because undiluted primer adheres poorly to waterproof concrete.
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