Hello and good evening,
I have a question regarding the planning of basement insulation.
We are planning to build an outdoor staircase at our house (built in 1959).
The height difference from the yard to the front door is 90cm (35 inches).
The front door is located in an extension we built in 2019.
The extension has no basement and only an 80cm (31.5 inches) deep foundation below the front door (measured from yard level down).
To the right, the old house has a basement (there is no slab-on-grade).
The basement is about 130cm (51 inches) deep from yard level down to the basement floor.
The basement walls are concrete walls without insulation or any other protection in the ground.
Now, instead of pallets, a large stone staircase is to be built.
The concrete slab in the yard will be removed.
For this, I plan to install formwork blocks shaped in a U to avoid damaging the base.
The base is insulated with XPS and plastered.
The actual stairs will be made with stone steps (not yet decided which type).
So far, that part is clear to me.
I will also pour an 80cm (31.5 inches) deep concrete footing under the formwork blocks.
Now comes my main question.
Four years ago, I excavated the entire front side of the house and insulated it with 5cm (2 inches) XPS, properly plastered and coated with bitumen.
The basement is not really damp, and there is no groundwater, but when the windows are closed, there is always a slight musty smell.
The basement floor consists of bricks.
The interior basement walls were painted a long time ago—now the paint is flaking off and the concrete is slightly sandy.
I suspect that low-quality cement was used back then.
Now the question is whether I should extend the insulation under the new entrance stairs down to the house foundation, or rather limit it to just the 80cm (31.5 inches) footings.
My main concern and fear is the risk of future settlement cracks and the shifting of the whole stair structure due to the excavation of the working space.
I will compact the soil, but I only have a small 60kg (132 lbs) vibrating plate compactor.
Would you take the risk and definitely insulate down to the foundation, or would you advise against it and instead place the footings on undisturbed ground?
Thank you in advance for your answers.
I hope the text is clear and not too complicated.
I have a question regarding the planning of basement insulation.
We are planning to build an outdoor staircase at our house (built in 1959).
The height difference from the yard to the front door is 90cm (35 inches).
The front door is located in an extension we built in 2019.
The extension has no basement and only an 80cm (31.5 inches) deep foundation below the front door (measured from yard level down).
To the right, the old house has a basement (there is no slab-on-grade).
The basement is about 130cm (51 inches) deep from yard level down to the basement floor.
The basement walls are concrete walls without insulation or any other protection in the ground.
Now, instead of pallets, a large stone staircase is to be built.
The concrete slab in the yard will be removed.
For this, I plan to install formwork blocks shaped in a U to avoid damaging the base.
The base is insulated with XPS and plastered.
The actual stairs will be made with stone steps (not yet decided which type).
So far, that part is clear to me.
I will also pour an 80cm (31.5 inches) deep concrete footing under the formwork blocks.
Now comes my main question.
Four years ago, I excavated the entire front side of the house and insulated it with 5cm (2 inches) XPS, properly plastered and coated with bitumen.
The basement is not really damp, and there is no groundwater, but when the windows are closed, there is always a slight musty smell.
The basement floor consists of bricks.
The interior basement walls were painted a long time ago—now the paint is flaking off and the concrete is slightly sandy.
I suspect that low-quality cement was used back then.
Now the question is whether I should extend the insulation under the new entrance stairs down to the house foundation, or rather limit it to just the 80cm (31.5 inches) footings.
My main concern and fear is the risk of future settlement cracks and the shifting of the whole stair structure due to the excavation of the working space.
I will compact the soil, but I only have a small 60kg (132 lbs) vibrating plate compactor.
Would you take the risk and definitely insulate down to the foundation, or would you advise against it and instead place the footings on undisturbed ground?
Thank you in advance for your answers.
I hope the text is clear and not too complicated.
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