Dear forum,
I am inexperienced with construction and am unsure if the procedure followed by our general contractor is correct:
My wife and I are currently having a single-family house built by a general contractor. The walls are made of lightweight expanded clay aggregate blocks. Due to a communication error, one wall (the inside of an exterior wall) was drilled with several holes. Depth about 8 cm (3 inches), diameter about 6 cm (2.5 inches). These were intended for toggle switches, but it was the wrong location. Now the holes have been filled again, using polystyrene boards, which were then plastered over. I only noticed this (the repaired spots were no longer visible) when I tapped the areas with my fingers and they sounded hollow. When tapping, I actually punched a small hole in one of these spots. The site manager said that the workers were instructed to do it this way, and that the surface was soft only because the plaster had not yet dried. The workers were there about 3 or 4 days ago.
As a layperson, I can’t imagine that this method complies with recognized technical standards. A solid wall made of expanded clay blocks patched with polystyrene boards and then plastered? These spots will surely remain weak points forever. If I lean too hard against the wall with my elbow, I might put a hole right there. Shouldn’t these holes be filled with something hard, like mortar or similar material?
I am inexperienced with construction and am unsure if the procedure followed by our general contractor is correct:
My wife and I are currently having a single-family house built by a general contractor. The walls are made of lightweight expanded clay aggregate blocks. Due to a communication error, one wall (the inside of an exterior wall) was drilled with several holes. Depth about 8 cm (3 inches), diameter about 6 cm (2.5 inches). These were intended for toggle switches, but it was the wrong location. Now the holes have been filled again, using polystyrene boards, which were then plastered over. I only noticed this (the repaired spots were no longer visible) when I tapped the areas with my fingers and they sounded hollow. When tapping, I actually punched a small hole in one of these spots. The site manager said that the workers were instructed to do it this way, and that the surface was soft only because the plaster had not yet dried. The workers were there about 3 or 4 days ago.
As a layperson, I can’t imagine that this method complies with recognized technical standards. A solid wall made of expanded clay blocks patched with polystyrene boards and then plastered? These spots will surely remain weak points forever. If I lean too hard against the wall with my elbow, I might put a hole right there. Shouldn’t these holes be filled with something hard, like mortar or similar material?
X
xMisterDx27 Feb 2024 23:44Are all the 150+ holes for power outlets, light switches, and roller shutter controls completely filled with mortar after the electrical work is connected?
With a decentralized ventilation system or an exhaust hood, you even have a 150mm (6 inch) thick hole in the exterior wall.
Lightweight expanded clay aggregate blocks are basically insulation blocks. Applying mortar directly to them...
If I ever get fed up with my fans, I plan to stuff the holes with polystyrene and definitely won’t seal the entire hole in the wall with mortar. That would create a perfect thermal bridge.
With an external thermal insulation composite system (ETICS), for example, mortar must not get into the joints between the insulation boards, as this would also create a thermal bridge.
With a decentralized ventilation system or an exhaust hood, you even have a 150mm (6 inch) thick hole in the exterior wall.
Lightweight expanded clay aggregate blocks are basically insulation blocks. Applying mortar directly to them...
If I ever get fed up with my fans, I plan to stuff the holes with polystyrene and definitely won’t seal the entire hole in the wall with mortar. That would create a perfect thermal bridge.
With an external thermal insulation composite system (ETICS), for example, mortar must not get into the joints between the insulation boards, as this would also create a thermal bridge.
A
Allthewayup28 Feb 2024 19:14Hmm, I don’t understand why no lightweight masonry mortar (LM21) or Tiroplan groove plaster was used there. Most likely, the general contractor used XPS. I don’t believe they actually installed EPS there?!
Is there a photo of the spot?
Is there a photo of the spot?
Allthewayup schrieb:
Hmm, I don’t understand why no lightweight masonry mortar (LM21) or Tiroplan slot plaster was applied. Most likely, the general contractor used XPS. I don’t think they actually inserted EPS in there?!
Is there a photo of that spot?I seem to recall the term Styrofoam was actually mentioned. In any case, neither XPS nor EPS.Fortunately, we have a photo:
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Allthewayup28 Feb 2024 20:00The fragments actually look more like EPS ("Styrofoam") than XPS. They appear to be about the same thickness as the impact sound insulation under the screed.
I’m not an expert on whether the general contractor (GC) is allowed to do this, but as a homeowner, I wouldn’t accept it. The significantly lower load-bearing capacity could cause problems if anything is ever mounted on this wall, especially in this particular spot.
Just kindly ask them to fill it with a building material that at least roughly matches the strength properties of your expanded clay aggregate. It doesn’t matter whether they use slot plaster or lightweight masonry mortar—either way, it’s definitely better than Styrofoam.
I’m not an expert on whether the general contractor (GC) is allowed to do this, but as a homeowner, I wouldn’t accept it. The significantly lower load-bearing capacity could cause problems if anything is ever mounted on this wall, especially in this particular spot.
Just kindly ask them to fill it with a building material that at least roughly matches the strength properties of your expanded clay aggregate. It doesn’t matter whether they use slot plaster or lightweight masonry mortar—either way, it’s definitely better than Styrofoam.
Thank you both for your responses. xMisterDx mentioned the issue of thermal bridging when using mortar. Is this not a concern with the options you suggested (lightweight masonry mortar LM21 or groove plaster)? At least according to Google, the LM21 lightweight masonry mortar is highly thermally insulating.
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