ᐅ Concrete slab without a screed layer on the upper floor/attic – what to do?
Created on: 21 Feb 2022 23:31
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christophenC
christophen21 Feb 2022 23:31Hello everyone,
In our house (new build, precast concrete), there is only screed on the ground floor. What is the best way to prepare the subfloor for the parquet?
Most neighbors are applying mainly a primer plus leveling compound. Then they use some kind of underlayment for impact sound insulation and install vinyl flooring. So, most are having a floating floor installed.
However, some parquet installers had concerns and were unsure how this would work without screed. They said that without screed, it might not be feasible due to sound insulation and residual moisture in the precast concrete elements.
As far as I understand, the height from the floor to the door lintel is not sufficient for screed either. Maybe the doors would need to be shortened.
How would you proceed? Would you still have screed installed (despite the high costs and the effort with the doors)? Or is a leveling compound enough?
We would like to install parquet everywhere. Do we need to consider anything specific if we don’t have screed underneath?
Thanks in advance for your help!
In our house (new build, precast concrete), there is only screed on the ground floor. What is the best way to prepare the subfloor for the parquet?
Most neighbors are applying mainly a primer plus leveling compound. Then they use some kind of underlayment for impact sound insulation and install vinyl flooring. So, most are having a floating floor installed.
However, some parquet installers had concerns and were unsure how this would work without screed. They said that without screed, it might not be feasible due to sound insulation and residual moisture in the precast concrete elements.
As far as I understand, the height from the floor to the door lintel is not sufficient for screed either. Maybe the doors would need to be shortened.
How would you proceed? Would you still have screed installed (despite the high costs and the effort with the doors)? Or is a leveling compound enough?
We would like to install parquet everywhere. Do we need to consider anything specific if we don’t have screed underneath?
Thanks in advance for your help!
P
pagoni202021 Feb 2022 23:42We have the whole house built this way, with just a concrete ceiling. Depending on the type of flooring you want to install, you can simply create a dry construction, and there are several options for that.
For example, in the bathroom we used a screed layer topped with Fermacell boards, then tiles on top. In the rest of the area, we laid battens floating on the floor, with Steico wood fiber insulation in between, and then screwed wooden floorboards on top. You can also screw OSB boards onto the battens and then install your flooring over that.
Why should that be a problem?
You don’t have to shorten doors. How many centimeters (inches) of floor build-up are currently possible on the upper floor?
What was the original plan, and why has it changed now?
For example, in the bathroom we used a screed layer topped with Fermacell boards, then tiles on top. In the rest of the area, we laid battens floating on the floor, with Steico wood fiber insulation in between, and then screwed wooden floorboards on top. You can also screw OSB boards onto the battens and then install your flooring over that.
Why should that be a problem?
You don’t have to shorten doors. How many centimeters (inches) of floor build-up are currently possible on the upper floor?
What was the original plan, and why has it changed now?
christophen schrieb:
In our house (new build, cast concrete), there is only screed on the ground floor. What is the best way to prepare the floor for parquet in this case? Who decided to omit the screed or failed to inform the planner about the intended floor coverings?
I usually only encounter this "issue" in developer-built terraced houses, which are designed to meet basic standards. Retrofitting not only runs into limitations with doors but also with staircases. For mid-terrace houses, I recommend accepting this and saving the more upscale features for the next step up the property ladder.
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Hello "christophen".
Parquet flooring is a building material with its own specific characteristics! It looks attractive, but unlike any other material, it reacts to changes in indoor humidity by expanding or contracting. Every type of parquet does!
When it comes to concrete floors, it is important to note that they usually have a surface flatness that allows parquet installation—but neither as a floating floor nor as full-surface adhesive bonding. Therefore, mechanical preparation is necessary, such as shot blasting or grinding, followed by priming and then leveling with a self-leveling compound.
This results in a flat (installation) substrate, but moisture released slowly from the concrete over a period of at least 2 to 5 years after curing will move toward the space with the lowest moisture potential.
To put it simply: In the years following the fresh concrete pour, the concrete will release its mixing water into the surrounding air.
The parquet flooring will absorb this moisture and expand or even become deformed as a result.
Therefore—this is my recommendation—you should discard the idea of "direct installation." Tiles can certainly be bonded directly onto a concrete substrate, but with parquet flooring there is an unpredictable risk of future floor damage due to deformation!
For this reason, any professional parquet installer should decline the project if it involves laying parquet directly on concrete.
The safest and most damage-proof method is to use a floating screed. This also conforms to building standards, which all specify a screed as the installation substrate.
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Regards, KlaRa
Parquet flooring is a building material with its own specific characteristics! It looks attractive, but unlike any other material, it reacts to changes in indoor humidity by expanding or contracting. Every type of parquet does!
When it comes to concrete floors, it is important to note that they usually have a surface flatness that allows parquet installation—but neither as a floating floor nor as full-surface adhesive bonding. Therefore, mechanical preparation is necessary, such as shot blasting or grinding, followed by priming and then leveling with a self-leveling compound.
This results in a flat (installation) substrate, but moisture released slowly from the concrete over a period of at least 2 to 5 years after curing will move toward the space with the lowest moisture potential.
To put it simply: In the years following the fresh concrete pour, the concrete will release its mixing water into the surrounding air.
The parquet flooring will absorb this moisture and expand or even become deformed as a result.
Therefore—this is my recommendation—you should discard the idea of "direct installation." Tiles can certainly be bonded directly onto a concrete substrate, but with parquet flooring there is an unpredictable risk of future floor damage due to deformation!
For this reason, any professional parquet installer should decline the project if it involves laying parquet directly on concrete.
The safest and most damage-proof method is to use a floating screed. This also conforms to building standards, which all specify a screed as the installation substrate.
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Regards, KlaRa
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Stefan00125 Feb 2022 11:51KlaRa schrieb:
To keep it simple: In the years following the fresh concrete installation, it will release its mixing water into the room air above. This is the first time I’ve noticed this here, but doesn’t concrete actually cure without drying out? The water is chemically bound within the concrete’s structure.
Is the well-known construction moisture excess water beyond that?
Stefan001 schrieb:
It occurs to me for the first time here: doesn’t concrete actually cure “without” drying? The water is chemically bound within the concrete structure.
Is the well-known construction moisture then excess water beyond that? Well, the answer to point 1 (doesn’t concrete actually cure “without” drying) is no!
If the concrete mix only contained the amount of water needed for the chemical reaction, the “dry mortar” could not be worked with at all.
For this reason, excess water (mixing water) must be added, which on the one hand chemically reacts with the cement, and on the other hand must physically evaporate. For thicker industrial floors, which are typically at least 15cm (6 inches) thick, the time to reach the indoor moisture level—especially when in contact with the ground—can take up to 12 years. Thinner concrete slabs in residential construction still require several years.
It is correct that the well-known construction moisture is caused by the necessarily excess water, but not only from concrete and screed, but also from drying excess water contained in the masonry walls and plaster.
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Best regards, KlaRa
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