Hello everyone,
I’m not very experienced in this area and hope someone can help me.
I have bought my grandparents’ house, which was built around 1950.
The floor and the lower 60 cm (24 inches) of the walls have become wet due to all the rain, and the basement is starting to develop mold.
The basement walls rest on strip foundations, and the basement floor is a simple screed on bare ground.
My plan is to remove the screed, layer the ground with crushed stone, install a moisture barrier membrane, pour concrete with steel reinforcement mesh, and then apply a screed on top.
However, I have seen that sometimes foam insulation boards (e.g., expanded polystyrene) are placed between the concrete and screed—does that make sense? Also, I would like to know what thickness of steel reinforcement mesh I should get.
Thank you in advance.
Best regards.
I’m not very experienced in this area and hope someone can help me.
I have bought my grandparents’ house, which was built around 1950.
The floor and the lower 60 cm (24 inches) of the walls have become wet due to all the rain, and the basement is starting to develop mold.
The basement walls rest on strip foundations, and the basement floor is a simple screed on bare ground.
My plan is to remove the screed, layer the ground with crushed stone, install a moisture barrier membrane, pour concrete with steel reinforcement mesh, and then apply a screed on top.
However, I have seen that sometimes foam insulation boards (e.g., expanded polystyrene) are placed between the concrete and screed—does that make sense? Also, I would like to know what thickness of steel reinforcement mesh I should get.
Thank you in advance.
Best regards.
Why do you want to use both concrete and screed? Unless you need a combination of high load-bearing capacity and a perfectly smooth surface for installing complex flooring (which is probably unlikely in a basement), you can achieve a good finish with trowel-finished concrete.
It might be possible to place Styrodur/XPS insulation under the concrete, but whether this makes sense depends on if and how the basement walls can or should be insulated.
However, I doubt that your approach will fundamentally solve the cause of the moisture. Normally, you would also need to include the walls in your waterproofing.
It might be possible to place Styrodur/XPS insulation under the concrete, but whether this makes sense depends on if and how the basement walls can or should be insulated.
However, I doubt that your approach will fundamentally solve the cause of the moisture. Normally, you would also need to include the walls in your waterproofing.
Harakiri schrieb:
Why do you want both concrete and screed? Unless you need a combination of high load capacity and a perfectly smooth floor for laying complex coverings (which is probably not the case in a basement), you can achieve a good surface with trowel-finished concrete.
It might be possible to install Styrodur/XPS insulation under the concrete, but whether this makes sense depends on if and how the basement walls can or should be insulated.
However, I doubt your plan will fundamentally solve the moisture issue. Typically, you would also need to include the walls in your waterproofing.Thank you very much for the information.
I’m a beginner in this field and had only read that some people apply screed over concrete. For me, it would not matter since I only want to use the basement rooms for storage.
Does this mean that after the gravel, the Styrodur/XPS insulation is laid and then the concrete on top?
Does the concrete need reinforcement on the strip footings, even though it technically doesn’t carry any load?
I have also read that a foil (plastic sheet) is sometimes placed between the concrete and the wall, but I haven’t understood the purpose of this.
Is it absolutely necessary to use steel mesh in the concrete, since the slab is theoretically not directly connected to the house/basement?
After the floor, the exterior walls are to be sealed and a drainage system also needs to be installed.
I looked into internal sealing using a low-pressure method, but that exceeds my budget.
Screed on concrete (usually with insulation and underfloor heating in between) is now standard, but it is probably unnecessary for you since the basement is likely unheated (?). If you skip the screed, you might even gain some ceiling height (depending on the situation). On the other hand, using screed makes sense if you plan to install a waterproofing membrane on your concrete slab – in that case, you could bring the membrane up the walls (ideally 30 cm (12 inches) or more, if it’s not possible to connect it to a damp-proof course) and then cover it with the screed. However, regarding waterproofing, I would definitely recommend consulting specialists first; there is a lot that can go wrong, especially in older buildings.
Whether you need to reinforce the concrete can only be properly assessed by a structural engineer. What loads do you intend to place on it? Do you plan to build interior walls on the slab? And so on – even if it costs a few hundred dollars, I would suggest having a professional review it before you start. Also, keep in mind that any reinforcement must be done carefully, particularly to ensure proper concrete cover. The concrete slab definitely needs to be separated from the strip footing. You could also consider fiber-reinforced concrete, but that must be planned by a professional and is usually only available as ready-mix concrete from a concrete plant (how do you plan to pour the concrete down there?).
Whether or not to include insulation and where to place it depends on the overall concept – for example, is the basement ceiling insulated with the space below unheated? Then adding insulation under the slab might have limited benefits. Or do you intend to insulate the basement walls from the inside? In that case, it would be more sensible to have insulation above the slab, connected to the internal wall insulation (with screed on top). Alternatively, if you plan to excavate and waterproof the basement walls from the outside, exterior insulation might make insulation under the slab attractive. Again, if you want to work efficiently, it’s advisable to have a complete plan made first. There are also plenty of subsidies available, maybe you can combine different measures?
Whether you need to reinforce the concrete can only be properly assessed by a structural engineer. What loads do you intend to place on it? Do you plan to build interior walls on the slab? And so on – even if it costs a few hundred dollars, I would suggest having a professional review it before you start. Also, keep in mind that any reinforcement must be done carefully, particularly to ensure proper concrete cover. The concrete slab definitely needs to be separated from the strip footing. You could also consider fiber-reinforced concrete, but that must be planned by a professional and is usually only available as ready-mix concrete from a concrete plant (how do you plan to pour the concrete down there?).
Whether or not to include insulation and where to place it depends on the overall concept – for example, is the basement ceiling insulated with the space below unheated? Then adding insulation under the slab might have limited benefits. Or do you intend to insulate the basement walls from the inside? In that case, it would be more sensible to have insulation above the slab, connected to the internal wall insulation (with screed on top). Alternatively, if you plan to excavate and waterproof the basement walls from the outside, exterior insulation might make insulation under the slab attractive. Again, if you want to work efficiently, it’s advisable to have a complete plan made first. There are also plenty of subsidies available, maybe you can combine different measures?
Important: Always consult a structural engineer beforehand. The term "schottern" suggests that after removing the screed, you might want to dig out further to add gravel. If this is done incorrectly, the house could literally collapse on you, so make sure to clarify the procedure thoroughly in advance.
If you do not include the walls in your plan, the whole effort will be quite ineffective regarding moisture and mold. However, renovating the walls can become very costly.
If you do not include the walls in your plan, the whole effort will be quite ineffective regarding moisture and mold. However, renovating the walls can become very costly.
Similar topics