A company is building a garage for me in lightweight concrete. However, I have noticed they have not placed any roofing felt between the slab and the first course but have instead placed some kind of sand/clay. I have no idea what this is. The slab is an insulated slab on the ground. How critical is it to have the roofing felt? I've received some different opinions on whether the felt is needed or not. Arguments against it are that the garage has an insulated slab with capillary-breaking properties and that the edge of the first course is protected with a strip that is installed when the facade is plastered. The size of the garage is 8x4.5 if that matters.
/molcam
/molcam
In the design guidelines for Ytong Energy, the following is stated:
Damp proof course under exterior wall
Normally, damp proof course, minimum quality of PF2000, is used under aerated concrete walls where the walls are constructed on a ground deck structure with underfloor heating extending under the back walls. This is particularly important when the ground deck structure expands lengthwise when heated – it's important to heat slowly at about 20 degrees. The damp proof course thus helps to detach some of the tensile forces related to the length expansion from the ground deck. Temperature expansions are usually largest during the first heating of winter constructions and in long buildings. Or use standard damp proof course solutions for masonry constructions. Glue-paper-glue solution can be used where load-bearing walls do not rest on the ground deck.
Damp proof course under partition wall
Normally, plastic wrap or paper is used as it prevents cohesion, i.e., adhesion to the ground deck, when ground decks can deform. This thereby avoids walls being undesirably affected by tensile forces related to the ground decks to the greatest extent possible.
Damp proof course under exterior wall
Normally, damp proof course, minimum quality of PF2000, is used under aerated concrete walls where the walls are constructed on a ground deck structure with underfloor heating extending under the back walls. This is particularly important when the ground deck structure expands lengthwise when heated – it's important to heat slowly at about 20 degrees. The damp proof course thus helps to detach some of the tensile forces related to the length expansion from the ground deck. Temperature expansions are usually largest during the first heating of winter constructions and in long buildings. Or use standard damp proof course solutions for masonry constructions. Glue-paper-glue solution can be used where load-bearing walls do not rest on the ground deck.
Damp proof course under partition wall
Normally, plastic wrap or paper is used as it prevents cohesion, i.e., adhesion to the ground deck, when ground decks can deform. This thereby avoids walls being undesirably affected by tensile forces related to the ground decks to the greatest extent possible.
Hello,
I must report a clearly differing opinion. I have never heard of the first shift being a movement joint. The cardboard is used to counteract vertical moisture migration and should remain sealed. In certain construction standards, even two horizontal moisture barriers need to be installed at a certain distance from each other.
I can understand that in Sweden they sometimes disregard the cardboard because the slab is supposedly capillary protected. But in my opinion, this reduces the safety against moisture migration.
I must report a clearly differing opinion. I have never heard of the first shift being a movement joint. The cardboard is used to counteract vertical moisture migration and should remain sealed. In certain construction standards, even two horizontal moisture barriers need to be installed at a certain distance from each other.
I can understand that in Sweden they sometimes disregard the cardboard because the slab is supposedly capillary protected. But in my opinion, this reduces the safety against moisture migration.
I think larsa means the sand which I didn't know what it was. Marmi, it was exactly the text I was looking for. What surprises me is that there is no mention of moisture in the text, which is why I thought you laid the paper. Regardless, I have received information from our ka, another construction company, as well as from the designer and the builder themselves that you don't need the paper if you have a slab on grade. So 4 have said it's OK to go without paper. Then the fact that ka would prefer to see it is probably mostly because it's his job to make sure Swedish practice is followed...