Hello
In the bedroom of our old house, we removed the old flooring along with the Mehabit screed. This left a gap along the edge of the wall.
We are now looking for a suitable mortar to fill this gap.
My next question is about the floor. Sandstones from the house wall appeared along the edge. We plan to pour Weber leveling compound over the floor to even out an uneven surface.
Can I pour the compound directly over the stones with a reinforcing mesh and primer applied beforehand, or do the stones need to be treated with a suitable plaster first?
Kind regards,
Natascha
In the bedroom of our old house, we removed the old flooring along with the Mehabit screed. This left a gap along the edge of the wall.
We are now looking for a suitable mortar to fill this gap.
My next question is about the floor. Sandstones from the house wall appeared along the edge. We plan to pour Weber leveling compound over the floor to even out an uneven surface.
Can I pour the compound directly over the stones with a reinforcing mesh and primer applied beforehand, or do the stones need to be treated with a suitable plaster first?
Kind regards,
Natascha
Hi Natascha,
Sandstone is one of those materials that can be quite tricky, even if it looks harmless. Just applying any coating usually holds up only until the first winter, then you get flaking and wonder why. Cement render would generally be the wrong choice here, as it is too hard and traps moisture, which doesn’t work well with sandstone.
A more sensible option is a lime or lime-cement render, depending on the condition of the stone. If the stone is rather soft and absorbent, I would even recommend a pure lime plaster, as it is more flexible and forgiving. It’s important to dampen the substrate well beforehand; otherwise, the stone will draw moisture out of the plaster faster than you want, and it won’t adhere properly.
A bonded screed on top is fine, but then the question is how high you plan to build up in total and whether you include a separation layer. I wouldn’t apply it directly onto fresh plaster. Have you considered how to properly detail the transition between wall and floor, especially regarding moisture and movement?
And honestly, with uneven floors the cause is often deeper than you think. Are you sure you don’t have any ongoing settlement or is it really just due to the old construction? A small oversight here can cause problems later on.
Sandstone is one of those materials that can be quite tricky, even if it looks harmless. Just applying any coating usually holds up only until the first winter, then you get flaking and wonder why. Cement render would generally be the wrong choice here, as it is too hard and traps moisture, which doesn’t work well with sandstone.
A more sensible option is a lime or lime-cement render, depending on the condition of the stone. If the stone is rather soft and absorbent, I would even recommend a pure lime plaster, as it is more flexible and forgiving. It’s important to dampen the substrate well beforehand; otherwise, the stone will draw moisture out of the plaster faster than you want, and it won’t adhere properly.
A bonded screed on top is fine, but then the question is how high you plan to build up in total and whether you include a separation layer. I wouldn’t apply it directly onto fresh plaster. Have you considered how to properly detail the transition between wall and floor, especially regarding moisture and movement?
And honestly, with uneven floors the cause is often deeper than you think. Are you sure you don’t have any ongoing settlement or is it really just due to the old construction? A small oversight here can cause problems later on.
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