Hello everyone,
I am new to this forum and a proud homeowner.
However, I have a question and hope someone can give me some advice.
The house was built in 1890, with brick masonry and timber framing on the upper floor.
I am currently renovating it and have almost stripped it down to the shell.
The original plan was to remove the screed down to the slab, install insulation, and put in underfloor heating.
But what I realized is that there is no concrete slab; part of the house stands on a vaulted cellar filled with ash, and the larger part rests on clay soil.
The ground is somewhat uneven—I have removed about 40 cm (16 inches) on one side and around 20 cm (8 inches) on the other.
So, theoretically, there is plenty of space to insulate, but how to do this without a concrete slab?
I was thinking of using a filler material to level the surface, maybe an insulation board like XPS, then a studded membrane for the underfloor heating pipes, and then pouring an anhydrite screed on top. But will that hold?
The heating engineer is unsure whether the insulation boards can withstand this. He said the screed would weigh about 75 kg/m² (15.4 lbs/ft²).
How should the fill material below the insulation boards be compacted? I was thinking of using a vibrating plate compactor, but I’m concerned it might cause cracks in the load-bearing walls. Does anyone have any ideas?
Good luck
Melden
I am new to this forum and a proud homeowner.
However, I have a question and hope someone can give me some advice.
The house was built in 1890, with brick masonry and timber framing on the upper floor.
I am currently renovating it and have almost stripped it down to the shell.
The original plan was to remove the screed down to the slab, install insulation, and put in underfloor heating.
But what I realized is that there is no concrete slab; part of the house stands on a vaulted cellar filled with ash, and the larger part rests on clay soil.
The ground is somewhat uneven—I have removed about 40 cm (16 inches) on one side and around 20 cm (8 inches) on the other.
So, theoretically, there is plenty of space to insulate, but how to do this without a concrete slab?
I was thinking of using a filler material to level the surface, maybe an insulation board like XPS, then a studded membrane for the underfloor heating pipes, and then pouring an anhydrite screed on top. But will that hold?
The heating engineer is unsure whether the insulation boards can withstand this. He said the screed would weigh about 75 kg/m² (15.4 lbs/ft²).
How should the fill material below the insulation boards be compacted? I was thinking of using a vibrating plate compactor, but I’m concerned it might cause cracks in the load-bearing walls. Does anyone have any ideas?
Good luck
Melden
I have no issues with the ceiling height; it was 2.70 m (8 ft 10 in), now it is between 2.90 and 3.00 m (9 ft 6 in and 9 ft 10 in).
I have also cleared everything out of the bathroom. The neighbor, who is around 80 years old, mentioned yesterday that no clay was filled in, but rather that we are on clay soil.
This means that clay soil is present throughout.
So, I don’t need to worry about the thickness. I saw that a company specializing in foam glass claims that foam glass gravel replaces the concrete slab, the lean concrete layer, and drainage, while also providing some insulation. But who has experience with this? Apparently, only a fleece must be laid before the screed.
I have also cleared everything out of the bathroom. The neighbor, who is around 80 years old, mentioned yesterday that no clay was filled in, but rather that we are on clay soil.
This means that clay soil is present throughout.
So, I don’t need to worry about the thickness. I saw that a company specializing in foam glass claims that foam glass gravel replaces the concrete slab, the lean concrete layer, and drainage, while also providing some insulation. But who has experience with this? Apparently, only a fleece must be laid before the screed.
Melden schrieb:
that the clay was not filled in, but that we are on clay soil.Yes and no. A rammed clay floor can definitely be made from the clay already present on site, but it is usually compacted in layers. Just not brought in separately. Where the existing composition was suitable, this is possible and practical.
Melden schrieb:
I have no problem with the ceiling height,and what about the lintel heights?
Melden schrieb:
I saw that a glass foam company claims their glass foam gravel replaces the concrete floor, the leveling layer, and drainage, while also providing some insulation. But who has experience with this? Apparently, only a fleece needs to be laid under the screed.I haven’t looked into that yet. The fleece is probably meant to prevent the flowing screed from flowing around the glass foam granules, enclosing them, and thus forming a layer together. That sounds logical to me.
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The XPS boards can support the weight of the floor, but they must be laid completely level. There should be a leveling layer underneath, which must also be firmly bonded once installed. At least this part should be done by a professional company. How is it being ensured that moisture from below does not penetrate the walls when the entire structure is built directly on clay soil, apart from the bearing capacity of the clay?
Depending on how many centimeters (cm) are added, the lintel may not need to be changed or at most one door lintel.
XPS would be an alternative, but I am missing the substructure for that. The walls still need to be braced horizontally. The concrete slab in the kitchen had damage, likely due to moisture, and there was bitumen under the screed in the bathroom. The clay seems to bear well, at least for the past 126 years. The basemented part only became wet after the city removed the clay and replaced it with sand.
XPS would be an alternative, but I am missing the substructure for that. The walls still need to be braced horizontally. The concrete slab in the kitchen had damage, likely due to moisture, and there was bitumen under the screed in the bathroom. The clay seems to bear well, at least for the past 126 years. The basemented part only became wet after the city removed the clay and replaced it with sand.
Elina schrieb:
How is moisture prevented from rising up into the walls when the whole structure stands directly on clay soil, aside from the load-bearing capacity of clay?Oh, I had assumed biologists were natural scientists. Clay is an excellent moisture regulator – precisely because of the clay, the indoor climate remains very stable. The load-bearing capacity after tamping is excellent; it becomes as solid as dry rye bread. Typically, rammed clay and rammed concrete were combined to achieve an optimal fit. This approach is gradually making a comeback. Building techniques are also a part of cultural heritage.
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I also studied geology – a biologist actually knows little about clay. A geologist does. For example, clay, meaning layers of clay and silt, forms water-impermeable layers and can never dry out completely (due to bound water). When wet, it tends to deform plastically; on inclined layers – no idea how it is in the original poster’s case – this may lead to sliding of the layers. It basically depends on how dry the whole thing is (but it will never be completely dry, as mentioned), how the layers are arranged, and how moisture input looks like, for example, during heavy rain.
Even the driest clay is “relatively” wet. Regarding load-bearing capacity – not necessarily the floor fill but rather what the house rests on – the question is therefore justified after all.
Even the driest clay is “relatively” wet. Regarding load-bearing capacity – not necessarily the floor fill but rather what the house rests on – the question is therefore justified after all.
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