ᐅ Fast-setting screed: advantages, disadvantages, additional cost, experiences?

Hello forum community,

I have received a quote for fast-drying screed with an additional cost of 1500 euros for about 120 m² (1290 ft²). According to the offer:

The cement-based fast-drying screed (VELOX 7 cement fast-drying screed) offers, compared to the usual screed system, the advantage that it can be walked on 24 hours after installation and can bear 70% of the contractual load from the 4th day after installation. By using fast-drying screed, you can save approximately 4 weeks of drying time.

From a financial point of view (4 weeks), I would save one month’s rent and one month of loan interest, which amounts to about 1900 euros. Would this be worthwhile? Especially since I’m not sure if the following trades would be available in time, and the time gain might be lost.

According to Google:
A conventional cement screed is walkable after about 3 days and can carry light loads after about one week, but it only reaches readiness for covering or full load-bearing capacity after at least 4 weeks. The screed is ready for covering when its residual moisture corresponds to the ambient air humidity.

During the drying phase, I plan to apply at least Q3 or Q4 level joint compound to the walls, meaning I would be working there after one week. Would this cause any issues regarding screed walkability?

P.S. The drywall installation inside the house is already finished, I hope this is not a disadvantage.

It’s not like I can just spend this extra amount without thinking. I’m still unsure. Who here has experience with this?

We had 5 construction dryers running for another 4 weeks until the approval and measurement were okay (normal screed).
With colleagues, it was dry at the first measurement by the tiler, but when the carpenter relied on that a week later or so, the parquet flooring probably warped later due to new moisture in the meantime and had to be removed again.

... I can’t contribute much to your question, just wanted to emphasize once more that it’s better to have the values right here 🙂

Standard screed actually needs about three weeks before you can start the heating program (which then takes at least another three weeks).
When and how can you work with your screed? What protocol did you receive from the screed installer regarding the underfloor heating?
However, the additional cost is quite significant!

I had a version where I was able to glue down the parquet after just over a week. That saved me six weeks in total.

Whether the additional costs are worth it is something you have to decide.

For our first house, we had to use fast-drying screed because there were delays, but the following trades were scheduled and the move-out date from our rental apartment was approaching, so we had no other choice. Of course, the actual measured values determine when the floor is ready for covering, not just the general information provided by the manufacturer, but in our case, they matched quite closely.

This time, we will use fast-drying screed again because I want to finally get things finished and I’m tired of the endless waiting 😉 .

allstar83 schrieb:

In our case, five drying units stayed inside for another four weeks until approval and measurement were okay (normal screed).
At a colleague’s place, it was dry at the first measurement by the tiler, but when the carpenter relied on that measurement a week or so later, the parquet floor warped later on (probably due to new moisture in the meantime) and had to be removed.
(...)

I would rather assume that the tiler measured in the bathroom, where, for whatever reasons, the screed was already ready for covering.
In bathrooms, underfloor heating is usually installed more closely spaced because it is designed for a higher temperature.

The parquet installer then simply laid the floor in the living room, even though he should have measured there again himself… he definitely included the CM measurement in his offer.

I am not a fan of rushing everything and would rather save that money.
Because you say it yourself:
In the end, the following trades do not start immediately afterward, so the construction sits idle for four weeks and you end up paying extra plus rent/construction period interest. You can walk on normal cement screed after just a few days. Otherwise, how would you be able to ventilate three times a day from the fourth or fifth day on…
Only point loads should be avoided for some time, so you shouldn’t climb a ladder with a 50kg (110 lbs) sack on your shoulders.

If you plan to do the work yourself anyway, there is no reason to speed up the construction process with fast-setting screed.
Smoothing and sanding all walls to Q4 will certainly take you two to three weeks. Can you do that?

The term "fast screed" does not provide any clear information without additional details from the manufacturer.
What exactly does the "fast" refer to?
Is it the early setting time, allowing quick use by subsequent trades, or is it the rapid water binding, which leads to quick readiness for covering?
There are screed binders that offer both properties.
However, these are naturally more expensive than a standard binder.
While the early strength development can generally be relied upon according to the manufacturer's specifications, the rapid readiness for covering is more variable.
This is because drying conditions also depend on the surrounding environment, meaning the climatic conditions on the construction site.
For example, if relative humidity of about 80% is present due to newly applied wall plaster or similar, drying cannot and will not occur.
Therefore, according to the manufacturer’s instructions, cross-ventilation must be provided, and the indoor climate conditions should be monitored and preferably documented with a thermometer/hygrometer.
The screed installer has just as little influence on the drying behavior as the binder manufacturer!
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It is also correct that cement-bound screeds can reabsorb moisture if the surrounding indoor humidity is high, even after the installation readiness has been confirmed by a CM (calcium chloride) test.
In a project I worked on, a luxuriously equipped, heritage-listed villa, the high-quality parquet had to be completely removed after the flooring installer laid it seven months after the initial installation (which was otherwise excellently executed). This was far too late after the CM measurement.
Therefore, the points mentioned here on this topic must be observed: a fast-drying screed cannot be meaningfully used if the subsequent trades cannot proceed timely.
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Construction is a complex, highly interesting field full of pitfalls for non-experts!
Regards, KlaRa