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harkonsen8 Jan 2024 21:11Hello everyone,
We have a cast asphalt screed in a 40 m² (430 sq ft) room with about a 5 mm (0.2 inch) difference in floor height.
Channels will be milled into the cast asphalt to install underfloor heating pipes.
Now, the screed specialist wants to level the floor heights. Skimming would be the thinnest option but also expensive. He plans to apply a calcium sulfate screed (because its expansion properties are similar to cast asphalt). This would result in a total floor buildup of about 15 mm (0.6 inch) at the higher spots.
My question is how important is it to level the floor with another material here, and why is this leveling actually so important?
Thank you!
We have a cast asphalt screed in a 40 m² (430 sq ft) room with about a 5 mm (0.2 inch) difference in floor height.
Channels will be milled into the cast asphalt to install underfloor heating pipes.
Now, the screed specialist wants to level the floor heights. Skimming would be the thinnest option but also expensive. He plans to apply a calcium sulfate screed (because its expansion properties are similar to cast asphalt). This would result in a total floor buildup of about 15 mm (0.6 inch) at the higher spots.
My question is how important is it to level the floor with another material here, and why is this leveling actually so important?
Thank you!
For heaven’s sake: Who would attempt something like this????
Cast asphalt screeds typically have a thickness of about 35mm (1.4 inches) in residential construction.
Heating elements are usually about 12mm (0.5 inches) thick.
Besides the fact that the heating elements in cast asphalt screeds are made of heat-resistant copper and embedded in the brushable bitumen compound, a retrofit installation, which is not recommended, would only result in a screed thickness of approximately 35mm - 12mm = 23mm (0.9 inches).
What clearly emerges here is a special construction for which there is no evidence that it will work in practice.
Completely outside of established technical standards!!!
What will happen?
Well, bitumen, the binder in every cast asphalt screed, unlike mineral screeds, is ultimately a viscous material that tends to flow under the influence of temperature.
As soon as milling takes place in the bituminous existing screed, predetermined breaking points will develop!
Even reworking with a mineral leveling compound will be the final blow to the cast asphalt screed.
Even if, as stated, it is supposed to be a calcium sulfate-based leveling compound.
This will not work – damage to the floor is inevitable, and complete failure of both the entire screed and the newly installed heating system is to be expected.
Whatever is being planned here – by whoever – is doomed to fail after the first use! Without any doubt.
-------------------
In the hope that my words will be taken into account (otherwise we will probably meet at an on-site court hearing for evidence collection):
KlaRa
Cast asphalt screeds typically have a thickness of about 35mm (1.4 inches) in residential construction.
Heating elements are usually about 12mm (0.5 inches) thick.
Besides the fact that the heating elements in cast asphalt screeds are made of heat-resistant copper and embedded in the brushable bitumen compound, a retrofit installation, which is not recommended, would only result in a screed thickness of approximately 35mm - 12mm = 23mm (0.9 inches).
What clearly emerges here is a special construction for which there is no evidence that it will work in practice.
Completely outside of established technical standards!!!
What will happen?
Well, bitumen, the binder in every cast asphalt screed, unlike mineral screeds, is ultimately a viscous material that tends to flow under the influence of temperature.
As soon as milling takes place in the bituminous existing screed, predetermined breaking points will develop!
Even reworking with a mineral leveling compound will be the final blow to the cast asphalt screed.
Even if, as stated, it is supposed to be a calcium sulfate-based leveling compound.
This will not work – damage to the floor is inevitable, and complete failure of both the entire screed and the newly installed heating system is to be expected.
Whatever is being planned here – by whoever – is doomed to fail after the first use! Without any doubt.
-------------------
In the hope that my words will be taken into account (otherwise we will probably meet at an on-site court hearing for evidence collection):
KlaRa
KlaRa schrieb:
Hoping my comments will be taken into consideration Even though I am not the thread starter, I found the explanation interesting. Are there alternative approaches if there is a cast asphalt screed in the existing structure, or is it usually completely replaced?
mayglow schrieb:
Even as someone who didn’t start the thread, I found the explanation interesting. Are there alternative approaches if there is an existing poured asphalt screed, or would it typically be completely replaced?There are definitely solutions for that! Depending on the local situation, the poured asphalt screed can be trimmed back on both sides by about 30-40cm (12-16 inches) in total.
The "gap," meaning the resulting damaged area, is then properly and professionally ramped.
What sounds simple comes with certain practical challenges, because poured asphalt in residential construction is installed over an insulation layer, making the surface ductile at the damaged spot. If you simply fill that space, the edges of the poured asphalt on both sides would break off under load. Also, so-called "dowel fixing" would be ineffective here since it cannot work with poured asphalt.
However, in this case, as a special construction, you could completely remove the insulation layer at the damaged area, create a composite structure with the concrete slab using a reactive resin mortar, and connect the two poured asphalt areas (resting on insulation) with a roughly 8mm (0.3 inch) wide movement joint.
This joint could later be filled with an elastic reactive resin before installing the final floor covering.
The drawback (if it can be called that) is that these two joints would need to be transferred—though not necessarily at the full width of the movement joint—to the floor surface.
This is indeed a special construction but, unlike retrofitted heating elements, it would work!