ᐅ Very thin screed with soil underneath – what to do?

Created on: 18 Aug 2021 21:16
M
Murkoff
In an old building (part of a farmhouse), the rear section is being renovated. After chipping out parts of the walls, especially in the bathroom, it became clear that there is approximately 8cm (3 inches) of screed. (Apparently, this consists of three layers, as it breaks in layers when chipped: two layers of about 4cm (1.5 inches) each, seemingly made of the same material, and a top layer of about 1cm (0.4 inches) – presumably a leveling compound.)

Since removing the floor to dig deeper and install insulation would be a lot of work, this option is being discarded. Installing insulation on the existing floor and then adding another screed layer would be possible given the room height of 3m (10 feet), but this is also avoided due to the effort involved. Since we manage around 30 hectares (74 acres) of forest and do not need to economize on wood chips or firewood, any potentially higher heating cost is not a concern. That is my current reasoning.

In the bathroom (7m² (75 sq ft)), the entire floor will be removed and redone because too much has been chipped out there. An electric underfloor heating system will also be installed beneath the tiles.

Here are my main questions: Is heating without insulation effective? What is the best floor structure for tiles? Is a simple screed (how thick?) with a decoupling membrane sufficient?

In the other rooms, there are some minor uneven spots. Should the floor be ground down or is it enough to apply a leveling compound?
M
Murkoff
19 Aug 2021 09:28
As far as I can see, there are two options:

01. Consider the rammed concrete as the structural floor slab and apply a moisture barrier, 6cm (2.4 inches) of insulation, and 6cm (2.4 inches) of screed on top.

02. Remove the rammed concrete, dig deeper, possibly add a fill layer, and then apply a moisture barrier, 6cm (2.4 inches) of insulation, and 6cm (2.4 inches) of screed to maintain the room height.
N
nordanney
19 Aug 2021 10:00
Murkoff schrieb:

As far as I can see, there are two options:
01. Consider the rammed concrete as a raw ceiling and apply a moisture barrier, 6cm (2.4 inches) of insulation, and 6cm (2.4 inches) of screed on top.
02. Remove the rammed concrete, dig deeper, possibly add a fill layer, then apply a moisture barrier, 6cm (2.4 inches) of insulation, and 6cm (2.4 inches) of screed to maintain the room height.
Option 1 is obviously the simplest. And with good PUR/PIR insulation, you can achieve quite a lot. Although more insulation would be better (a thinner screed could also be used, even with underfloor heating).
M
Murkoff
19 Aug 2021 10:13
With option two, it would be even easier to install underfloor heating.

What would be the minimum construction setup for option one? In my previous response, I only provided approximate values.
Is impact sound insulation necessary if there is only a ground floor without a basement and no upper floor? In other words, is impact sound also transmitted to adjacent rooms?
11ant19 Aug 2021 10:30
Murkoff schrieb:

How should the new screed be installed on the rammed concrete?
Floating?

Unfortunately, I can’t tell you either – @KlaRa knows the most about flooring here – but I’d consider floating screed pointless in this case; it’s hard to slide on such a rough surface ;-)
Myrna_Loy schrieb:

Electric underfloor heating is pointless without insulation there as well.

Using wood chips from your own forest to generate electricity for heating would be nonsense times three *LOL*
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A
apokolok
19 Aug 2021 10:55
I would definitely excavate everything completely.
If you just build on top, the door heights won’t fit anymore.
New lintels are also quite a lot of work.
With a mini excavator, it should be doable since just a few centimeters (inches) are needed.
M
Murkoff
19 Aug 2021 11:02
How can I prevent interior walls from sinking or developing cracks in option 2 if I excavate too close to them?