I have a brick villa with a lightweight concrete frame and cast-in-place floor slabs between the ground floor and attic (and basement). The roof is a wooden construction with boarding and asbestos cement on top, which has then been clad with sheet metal. We now want to cut an opening for an attic ladder (hatch in the ceiling) and prepare certain areas in the attic to store things there. Simply laying some tongue-and-groove boards as flooring works fine; we don't need a better surface than that. In conjunction with this, I want to change the insulation material from the current to something less flammable than wood chips... Today, this is how the floor in the attic is: cast concrete floor slab, followed by wood chips (~10-15 cm), on top of that a plastic sheet and then additional insulation which has been added later (I guess) consisting of mineral wool mats (5 cm in its current state). I could consider insulating more, but it must not result in moisture problems in the attic. A professor in building technology warned me about simply adding more insulation without looking at the overall situation, as it can cause moisture on the interior ceiling with certain weather conditions if everything is not done correctly.
I want to maintain the ceiling height in the central passage, so there I can sacrifice some insulation and use some good cell plastic that might be sold cheaply right now... On the sides where you don't normally walk (and therefore can sacrifice some ceiling height), I think of insulating a little better than now, maybe except for the very outermost where it's hard to reach. I'm not planning to re-insulate the entire attic, but the central passage will be completely remodeled and then maybe 1/3 of the house's length (i.e., ~5 meters) on each side.
For the storage area, I'm planning to build like this:
Wood floor, planed tongue-and-groove boards (cheap options?)
Mineral wool 12 cm to match new 120 mm joist (is more needed?)
Plastic sheet (vapor barrier/sealing layer)
Concrete slab
I also need to build up joists as there is only a single longitudinal joist in the attic (I thought there would be joists along each roof truss, but there aren't), so I can determine the height of the insulation there.
How do I handle insulation and sealing on the areas where I lay flooring? An exterior wall should normally have sealing toward the inside of the house and then insulation outward. Here, at best, I can place sealing (plastic sheet) between the concrete and mineral wool (which I guess is the best choice). Does the concrete let through any significant amounts of moisture, making it worthwhile to apply a plastic sheet? Would it be "incorrect" to place a plastic sheet between concrete and mineral wool?
We don't have an attic ladder today but planned to let a company cut an opening for one with dimensions 700x1400 or 860x1300 mm:
https://www.stegfabriken.se/p/fakro-lwf-bd45-lofttrappe/?tax_display=2?tax_display=2
The hallway where the hole will be made is 470 x 290 cm, and the hole will be cut lengthwise in the room with a short side near a short side of the room. The short side of that room is a load-bearing wall in cast concrete (17 cm thick) and not lightweight concrete like the other interior and exterior walls. It shouldn't cause strength issues even if we cut a hole of that size in the concrete slab, should it? There is plenty of reinforcement, and the slab is, as mentioned, from 1962, so it should be of good quality. It's quite tough to drill into anyway (though not the toughest I've tackled).
Okay, that turned into a long post with lots of questions, but there are two important things here: moisture issues due to re-insulation and the strength of the slab at the attic ladder's opening.
Anyone have the stamina to read and comment?
/Fredrik
I want to maintain the ceiling height in the central passage, so there I can sacrifice some insulation and use some good cell plastic that might be sold cheaply right now... On the sides where you don't normally walk (and therefore can sacrifice some ceiling height), I think of insulating a little better than now, maybe except for the very outermost where it's hard to reach. I'm not planning to re-insulate the entire attic, but the central passage will be completely remodeled and then maybe 1/3 of the house's length (i.e., ~5 meters) on each side.
For the storage area, I'm planning to build like this:
Wood floor, planed tongue-and-groove boards (cheap options?)
Mineral wool 12 cm to match new 120 mm joist (is more needed?)
Plastic sheet (vapor barrier/sealing layer)
Concrete slab
I also need to build up joists as there is only a single longitudinal joist in the attic (I thought there would be joists along each roof truss, but there aren't), so I can determine the height of the insulation there.
How do I handle insulation and sealing on the areas where I lay flooring? An exterior wall should normally have sealing toward the inside of the house and then insulation outward. Here, at best, I can place sealing (plastic sheet) between the concrete and mineral wool (which I guess is the best choice). Does the concrete let through any significant amounts of moisture, making it worthwhile to apply a plastic sheet? Would it be "incorrect" to place a plastic sheet between concrete and mineral wool?
We don't have an attic ladder today but planned to let a company cut an opening for one with dimensions 700x1400 or 860x1300 mm:
https://www.stegfabriken.se/p/fakro-lwf-bd45-lofttrappe/?tax_display=2?tax_display=2
The hallway where the hole will be made is 470 x 290 cm, and the hole will be cut lengthwise in the room with a short side near a short side of the room. The short side of that room is a load-bearing wall in cast concrete (17 cm thick) and not lightweight concrete like the other interior and exterior walls. It shouldn't cause strength issues even if we cut a hole of that size in the concrete slab, should it? There is plenty of reinforcement, and the slab is, as mentioned, from 1962, so it should be of good quality. It's quite tough to drill into anyway (though not the toughest I've tackled).
Okay, that turned into a long post with lots of questions, but there are two important things here: moisture issues due to re-insulation and the strength of the slab at the attic ladder's opening.
Anyone have the stamina to read and comment?
/Fredrik
Do you not have a section drawing of the house that you can upload? Otherwise, it becomes a bit difficult.
The wood shavings are either sawdust or cutter shavings. Regardless, they are quite good materials if you have space for them. I don't think it's entirely successful that there is a plastic sheet between the shavings and the newer insulation. The main rule is, if you need it at all, to place the plastic as close to the warm side as possible.
The wood shavings are either sawdust or cutter shavings. Regardless, they are quite good materials if you have space for them. I don't think it's entirely successful that there is a plastic sheet between the shavings and the newer insulation. The main rule is, if you need it at all, to place the plastic as close to the warm side as possible.