Hello everyone,
this year we will be building a single-family house with approximately 200 m² (2,150 sq ft) of living space. The underfloor heating (air-to-water heat pump) is installed within the screed. The topic of screed is still quite unclear to me and it keeps occupying my mind. From research within this forum, many questions have already been raised and some qualified answers given, but the actual pros and cons are still not entirely clear to me (by the way, every company I ask says something different :-))
I will summarize my modest knowledge so far:
Cement screed (flowing screed):
Positive: water resistance
Negative: prone to cracking, prone to curling, somewhat more expensive, joints required on large surfaces
Cement screed (site-applied screed, smoothed):
Positive: water resistance, less water and therefore shorter drying time, less prone to curling
Negative: cracking risk?, much more expensive than anhydrite or flowing cement screed
Anhydrite screed:
Positive: no joints required on large surfaces, fairly inexpensive
Negative: water resistance
Question: How do these options behave in relation to the built-in underfloor heating? Anhydrite screed is often marketed as "heating screed." Is its performance really that much better than cement screed?
The interior finishing will be done entirely with drywall (gypsum plasterboards). Is my concern about the high moisture content with flowing screed justified (since gypsum plasterboards are known to absorb moisture) or is this negligible?
Considerations: Basically, I was leaning toward using fully cement screed (flowing screed) because it is self-leveling. However, I keep hearing concerns about curling and similar issues. The alternative of using the more labor-intensive and “drier” site-applied screed (smoothed) is reportedly quite expensive (but we have not received an offer yet).
Initially, anhydrite screed was not even considered, but the feature of being “joint-free” (kitchen, living, dining area is about 50 m² (540 sq ft)) makes it fundamentally interesting. My real concern here is the issue of water resistance.
I look forward to your experiences or suggestions.
Thank you
Sebastian
this year we will be building a single-family house with approximately 200 m² (2,150 sq ft) of living space. The underfloor heating (air-to-water heat pump) is installed within the screed. The topic of screed is still quite unclear to me and it keeps occupying my mind. From research within this forum, many questions have already been raised and some qualified answers given, but the actual pros and cons are still not entirely clear to me (by the way, every company I ask says something different :-))
I will summarize my modest knowledge so far:
Cement screed (flowing screed):
Positive: water resistance
Negative: prone to cracking, prone to curling, somewhat more expensive, joints required on large surfaces
Cement screed (site-applied screed, smoothed):
Positive: water resistance, less water and therefore shorter drying time, less prone to curling
Negative: cracking risk?, much more expensive than anhydrite or flowing cement screed
Anhydrite screed:
Positive: no joints required on large surfaces, fairly inexpensive
Negative: water resistance
Question: How do these options behave in relation to the built-in underfloor heating? Anhydrite screed is often marketed as "heating screed." Is its performance really that much better than cement screed?
The interior finishing will be done entirely with drywall (gypsum plasterboards). Is my concern about the high moisture content with flowing screed justified (since gypsum plasterboards are known to absorb moisture) or is this negligible?
Considerations: Basically, I was leaning toward using fully cement screed (flowing screed) because it is self-leveling. However, I keep hearing concerns about curling and similar issues. The alternative of using the more labor-intensive and “drier” site-applied screed (smoothed) is reportedly quite expensive (but we have not received an offer yet).
Initially, anhydrite screed was not even considered, but the feature of being “joint-free” (kitchen, living, dining area is about 50 m² (540 sq ft)) makes it fundamentally interesting. My real concern here is the issue of water resistance.
I look forward to your experiences or suggestions.
Thank you
Sebastian
S
Sebastian828 Mar 2021 10:56nordanney schrieb:
The other way around, cheap to expensive.
This surprises me, since for me (currently only 2 quotes) anhydrite is cheaper than flowing cement. For cement (ready-mix for construction sites), I expected an even higher amount, as the surface needs to be smoothed manually and with effort. Or does the material saving make such a big difference here?S
Sebastian828 Mar 2021 10:59Yes and no. The tiler should properly prepare the shower area, including drainage. This is usually not done by the screed installers. However, the tiler will not pour the screed for the entire bathroom. There is no reason, though, not to cover the bathroom floor with calcium sulfate screed and then seal it properly. A complete waterproofing layer is highly recommended even with “normal” screed.
Nowadays, tilers often handle this themselves when they can use their system (from a well-known tile accessory supplier) with a thin screed method. At least, that has been my experience.
Nowadays, tilers often handle this themselves when they can use their system (from a well-known tile accessory supplier) with a thin screed method. At least, that has been my experience.
On the topic of costs: I have several quotes for my home renovation. The cement screed was always the most expensive option. Eastern European screed installers just shovel a bit and then quickly pump the cement screed into the building with the machine. It’s not very labor-intensive ;-)
Sebastian82 schrieb:
Yes and no. The tiler should properly construct the shower area, including drainage. This is usually not done by the screed installers. However, the tiler will not apply the screed for the entire bathroom. There is no reason not to cover the bathroom floor with calcium sulfate screed and then waterproof it properly. Full waterproofing is highly recommended even with “standard” screed. Tilers nowadays often do this themselves if they can apply their system (from a well-known tile accessory supplier) using the thin screed method. This has been my experience, at least.
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What kind of screed system are you referring to? With 5cm (2 inches) thickness over 20m² (215 sq ft), no tiler really wants to mix and apply 1 cubic meter of screed by hand.
S
Sebastian828 Mar 2021 13:12What did you finally decide on? CA (fluid) despite the higher price?
Regarding the screed in the bathroom, several tilers offer a system from a manufacturer based in Iserlohn (I believe advertising is not desired...) where very little screed is applied over the appropriate insulation mats. It basically sounds good, as less screed means less thermal inertia during heating.
Regarding the screed in the bathroom, several tilers offer a system from a manufacturer based in Iserlohn (I believe advertising is not desired...) where very little screed is applied over the appropriate insulation mats. It basically sounds good, as less screed means less thermal inertia during heating.
Sebastian82 schrieb:
What did you ultimately decide on? Self-leveling compound (liquid screed) despite a higher quote? I have to go with 4.5cm (1.8 inches) self-leveling compound screed in the end, otherwise I won’t meet my build-up height requirements. But we’re only talking about a few hundred euros for 120 sqm (roughly 1,290 sq ft) – the price difference is about 2€ per square meter compared to regular screed. Honestly, it’s really unnecessary to worry about this aspect for the trade.