I have a question...!
A suggestion we have for expanding the living space at a reasonable cost is to convert our small unheated garage into living space.
The slab is not insulated underneath, but is built in the same way as the rest of the house - slab on grade with insulation above.
There is plastic on the slab in the house, then fiberglass and floor joists... it's worked fine for 25 years so far, so I thought I'd do the same in the garage.
However, I hope to be able to insulate with cellular plastic instead and skip the floor joists.
So what do you think about leveling the floor with self-leveling compound - gluing on 2x100mm cellular plastic - gluing gypsum board on it? It will be a non-load-bearing interior wall, and I can glue it onto the floor gypsum!?
Should I install a moisture barrier somewhere, or maybe the cellular plastic itself can function in the same way as the plastic in the house does today?
Unfortunately, I can't insulate more, as the ceiling height is limited.
Is one layer of gypsum enough, or should I use two layers, crisscrossed?
A suggestion we have for expanding the living space at a reasonable cost is to convert our small unheated garage into living space.
The slab is not insulated underneath, but is built in the same way as the rest of the house - slab on grade with insulation above.
There is plastic on the slab in the house, then fiberglass and floor joists... it's worked fine for 25 years so far, so I thought I'd do the same in the garage.
However, I hope to be able to insulate with cellular plastic instead and skip the floor joists.
So what do you think about leveling the floor with self-leveling compound - gluing on 2x100mm cellular plastic - gluing gypsum board on it? It will be a non-load-bearing interior wall, and I can glue it onto the floor gypsum!?
Should I install a moisture barrier somewhere, or maybe the cellular plastic itself can function in the same way as the plastic in the house does today?
Unfortunately, I can't insulate more, as the ceiling height is limited.
Is one layer of gypsum enough, or should I use two layers, crisscrossed?
You can safely skip the floor joists and lay foam with a floating floor.
BUT!!
The problem is that you lower the temperature in the concrete so that it becomes almost the same as the ground. Since it is said that there is 100% RH in the ground, it will also be the same in the concrete. The foam is not sufficient as moisture protection, so you need to have plastic between the concrete and the foam.
What kind of walls do you have? What does the sill connection look like?
This particular issue with the concrete getting higher RH than before can cause problems depending on how the sill is, as materials in contact with each other strive for equilibrium.
What will you use the space for? Why do you need gypsum on the floor?
I would go with floor chipboard instead, then you can screw as much as you want. If you plan to build some kind of wet area, you should be careful with double moisture barriers that trap the moisture inside.
Then it might be good to check what principles the municipality has concerning the change of usage..
BUT!!
The problem is that you lower the temperature in the concrete so that it becomes almost the same as the ground. Since it is said that there is 100% RH in the ground, it will also be the same in the concrete. The foam is not sufficient as moisture protection, so you need to have plastic between the concrete and the foam.
What kind of walls do you have? What does the sill connection look like?
This particular issue with the concrete getting higher RH than before can cause problems depending on how the sill is, as materials in contact with each other strive for equilibrium.
What will you use the space for? Why do you need gypsum on the floor?
I would go with floor chipboard instead, then you can screw as much as you want. If you plan to build some kind of wet area, you should be careful with double moisture barriers that trap the moisture inside.
Then it might be good to check what principles the municipality has concerning the change of usage..
The walls are made of wood, the sill likewise with a few layers of tar paper underneath.Tjippen said:
Same as the main house.
Hoping to replicate the method from the house to the garage to get as "harmonious" a house as possible.
There will be bedrooms, a living room, and a smaller wet area.
The wet room is adjacent – so I'll open it up to get plastic with a bathtub as well.
Gypsum on the floor was my first thought, simply, should work just as well to glue down chipboard instead of gypsum?
The municipality has been contacted and they were only positive and stated that it was most likely permit-free - should receive a document as proof of that at home.
A saved penny is a happy penny!
Regarding the insulation - which quality should I go for?
S80 should go a long way, but to be safe maybe I can lay 150mm S80 and top with 50mm S200, for any point loads?
OK, then the walls should be fine. Yes, you can go with drywall, but you should probably use double glued layers. Were you planning to install a new floor drain with a slope in the bathroom, or is the existing one sufficient? It might be worth doing something different there, as underfloor heating is really nice in the morning=) Unfortunately, I have no idea about the cellplast, but it can't hurt to take a harder one!
So regarding the floor gypsum, it would be double layers, against chipboard when I use a 22mm layer!?
Feels like I could save some money by choosing chipboard instead.
Floor drain, yes... I need a slight slope, but since it's such a small area, I should be able to level it with self-leveling compound, might as well throw in a heating cable while I'm at it. There are some regulations regarding chipboard + electric heating cables - but I've done it before in the hallway, so at least I know how it should be.
The foam plastic, yes... I don't really have much more information besides that S200 is harder than S80.
However, it seems logical to have a 50mm layer of harder material above the 150mm softer material, if you think there might be some point loads here and there.
A safe or something like that!
Thanks for the help so far!
Feels like I could save some money by choosing chipboard instead.
Floor drain, yes... I need a slight slope, but since it's such a small area, I should be able to level it with self-leveling compound, might as well throw in a heating cable while I'm at it. There are some regulations regarding chipboard + electric heating cables - but I've done it before in the hallway, so at least I know how it should be.
The foam plastic, yes... I don't really have much more information besides that S200 is harder than S80.
However, it seems logical to have a 50mm layer of harder material above the 150mm softer material, if you think there might be some point loads here and there.
A safe or something like that!
Thanks for the help so far!
Regardless of whether you have insulation under or over the slab, but especially if the insulation is underneath, my advice (as someone who works with these issues in research) is to lay a Platon mat (blue) on a leveled concrete floor, properly installed at the walls. On this (optional) subfloor foam (to eliminate creaking). On top of this, you can then place styrofoam insulation. The cheapest option on top (depending on desired floor appearance) is to lay a 14mm parquet floor. Other floors require chipboard flooring (which is not cheap) + top flooring.
This construction allows ventilation of the concrete slab. The garage floor is likely not as well made as the rest of the house, even if it appears to be. Today, your garage floor is so well-ventilated without anything on top that you don't have any problems. As soon as you change the construction, the moisture balance in the structure also changes. This also applies when taking measures for living space in the ceiling.
Concrete slab with possible (garage??) underlying insulation, plastic foil, overlying floor joists (with or without insulation) + floor surface is one of the greatest risk constructions we have from the 70s-80s regarding moisture and mold.
This construction allows ventilation of the concrete slab. The garage floor is likely not as well made as the rest of the house, even if it appears to be. Today, your garage floor is so well-ventilated without anything on top that you don't have any problems. As soon as you change the construction, the moisture balance in the structure also changes. This also applies when taking measures for living space in the ceiling.
Concrete slab with possible (garage??) underlying insulation, plastic foil, overlying floor joists (with or without insulation) + floor surface is one of the greatest risk constructions we have from the 70s-80s regarding moisture and mold.
I am fully aware that this is a risky construction, but I have some "evidence" that it will go well...
Firstly, the house's slab and the garage's slab are one and the same, i.e., they are connected and were made simultaneously, with the same form and execution regarding groundwork, etc.
Secondly, the house was built by my neighbors' father/father-in-law, and the man in the neighboring house is a carpenter who helped with the construction himself. He has confirmed that the garage slab has the exact same conditions as the rest of the house. (which is bone dry under the insulation)
Thirdly, the garage slab is currently painted with floor paint that is sealed - and it does not peel or show any problems with rising ground moisture.
So I feel as confident as I can be, since I did not build the house myself, that it will go well.
But thank you for the warning/tip!
Firstly, the house's slab and the garage's slab are one and the same, i.e., they are connected and were made simultaneously, with the same form and execution regarding groundwork, etc.
Secondly, the house was built by my neighbors' father/father-in-law, and the man in the neighboring house is a carpenter who helped with the construction himself. He has confirmed that the garage slab has the exact same conditions as the rest of the house. (which is bone dry under the insulation)
Thirdly, the garage slab is currently painted with floor paint that is sealed - and it does not peel or show any problems with rising ground moisture.
So I feel as confident as I can be, since I did not build the house myself, that it will go well.
But thank you for the warning/tip!