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
Let me double-check if I understood correctly: the part that concerns you is the non-basement section of the ground floor, where you have leveled the rammed earth floor to an approximately flat level, and which now rests directly on soil with an unknown (and likely uneven) thickness, causing unpredictable structural stability?
In that case, I would probably try to create a compacted subbase using rammed concrete.
I share your concerns about using mechanical vibrators.
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
In that case, I would probably try to create a compacted subbase using rammed concrete.
I share your concerns about using mechanical vibrators.
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
Good morning,
I have not removed anything from the clay floor; it was probably made this way over 100 years ago. For the past several decades, there has been a concrete screed with various additives on top, likely whatever was available at the time. My question or concern is: what can I use to level the surface, and can I place about 10 cm (4 inches) of insulation on it, or would that be too unstable? What load can such an insulation board support?
Thank you very much
I have not removed anything from the clay floor; it was probably made this way over 100 years ago. For the past several decades, there has been a concrete screed with various additives on top, likely whatever was available at the time. My question or concern is: what can I use to level the surface, and can I place about 10 cm (4 inches) of insulation on it, or would that be too unstable? What load can such an insulation board support?
Thank you very much
Melden schrieb:
For the past several decades, there has been a concrete screed with various additives on top, probably whatever was available.For a house from that era, I would expect there to be a (multi-layered) rammed earth layer with a similar rammed concrete layer on top. To put it simply, that ("various additives...") would be the recipe.
You can look both up online, as they are becoming popular again in historical renovations.
Melden schrieb:
What can I use to level the surface, and can I install about 10cm (4 inches) of insulation on top, or would that be too unstable? What load can such an insulation board bear?If I understand correctly: you want to use an insulation board, which would typically be placed under a new slab, here directly beneath a screed with embedded underfloor heating?
I’m not sure about the compressive strength these boards can handle. Additional forces would come into play here if the subfloor is not sufficiently load-bearing. I would be concerned that lateral forces could exceed the elasticity limits of the heating system installation.
Therefore, my thought is to recreate the original type of floor (just level). You could measure out the height using battens and finish with a self-leveling screed. But this is just an idea—I haven’t built this myself.
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
Yes, it could be rammed concrete. The plan is indeed to properly insulate the screed slab, for example with 10 cm XPS (4 inches) or, if using glass foam aggregate, about 20-30 cm (8-12 inches). The underfloor heating and screed would then be placed on top. I had hoped to avoid using concrete.
P
Peanuts7417 Feb 2017 08:57It will probably be difficult or only by chance to find the right solution in the forum for a case like this (from a distance).
At that age, don’t you have any issues with the ceiling height?
I still remember my mother’s childhood home, also from the 1800s, where ceiling heights were just over 2 meters (around 6.6 feet), walls made of clay that were probably smoothed by hand, and a small stream running through the basement.
In such a case, hoping for a concrete slab foundation seems very optimistic to me.
Would it be possible to excavate the current floor as much as possible, then add some kind of separation layer (crushed stone, gravel, etc.), and pour a thinner reinforced concrete slab or possibly a waterproof concrete (WU concrete) slab—without gravel underneath—within that, on which everything else is then built?
At that age, don’t you have any issues with the ceiling height?
I still remember my mother’s childhood home, also from the 1800s, where ceiling heights were just over 2 meters (around 6.6 feet), walls made of clay that were probably smoothed by hand, and a small stream running through the basement.
In such a case, hoping for a concrete slab foundation seems very optimistic to me.
Would it be possible to excavate the current floor as much as possible, then add some kind of separation layer (crushed stone, gravel, etc.), and pour a thinner reinforced concrete slab or possibly a waterproof concrete (WU concrete) slab—without gravel underneath—within that, on which everything else is then built?
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