ᐅ Uneven subfloor – how to calculate the amount of leveling compound needed?
Created on: 25 Oct 2023 01:14
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SarahMüller
SarahMüller25 Oct 2023 01:14Hello,
Calculating floor unevenness?
I want to renew the flooring in my mother’s living room (about 18sqm (194 sqft)). I’ve already removed the parquet, but unfortunately—or naturally—the floor is far from level.
How can I calculate the extent of the floor’s unevenness so I apply the right amount of leveling compound?
I’ve gathered some information already:
Place a self-leveling laser in the room, measure the highest points using a tape measure and the laser, then add up the measurements from different spots, divide by the number of measurement points, divide the result by 2, and then add 2mm (about 0.08 inches).
Example:
5mm + 3mm + 2mm + 5mm + 1.5mm + 2.5mm + 3mm + 6mm + 9mm + 4mm (etc.) = 41mm / 10 = 4.1mm
Divide that by 2 again to get 2.05mm, then add 2mm as a buffer, so I would need about 4.05mm layer thickness to level out the uneven floor completely.
I’m not 100% sure if this is correct. Should I use the first measurement as a reference, or always measure from the previous measurement? Or should I identify the highest point and use that as the reference?
I’m not sure if this is the right area of the forum.
Calculating floor unevenness?
I want to renew the flooring in my mother’s living room (about 18sqm (194 sqft)). I’ve already removed the parquet, but unfortunately—or naturally—the floor is far from level.
How can I calculate the extent of the floor’s unevenness so I apply the right amount of leveling compound?
I’ve gathered some information already:
Place a self-leveling laser in the room, measure the highest points using a tape measure and the laser, then add up the measurements from different spots, divide by the number of measurement points, divide the result by 2, and then add 2mm (about 0.08 inches).
Example:
5mm + 3mm + 2mm + 5mm + 1.5mm + 2.5mm + 3mm + 6mm + 9mm + 4mm (etc.) = 41mm / 10 = 4.1mm
Divide that by 2 again to get 2.05mm, then add 2mm as a buffer, so I would need about 4.05mm layer thickness to level out the uneven floor completely.
I’m not 100% sure if this is correct. Should I use the first measurement as a reference, or always measure from the previous measurement? Or should I identify the highest point and use that as the reference?
I’m not sure if this is the right area of the forum.
Pictures help us better assess the situation. What is the condition of the subfloor? Can you simply apply leveling compound there? Depending on the material, it requires a certain minimum thickness and must be compatible with the subfloor to avoid crumbling later under the newly installed parquet. What is the maximum buildup height you have? (Doors) Can you go deeper to optionally install insulation underneath? Do you want to install the flooring as a floating floor or fully glued down?
If you provide a bit more information, especially clear pictures, it always helps to get @KlaRa involved for questions like these ;-)
P.S. Regarding the quantity, you won’t be able to calculate it precisely, only estimate. Once you know which leveling compound you are allowed to use, buy enough and arrange a return option for unopened containers. In my experience, most hardware stores agree to this.
If you provide a bit more information, especially clear pictures, it always helps to get @KlaRa involved for questions like these ;-)
P.S. Regarding the quantity, you won’t be able to calculate it precisely, only estimate. Once you know which leveling compound you are allowed to use, buy enough and arrange a return option for unopened containers. In my experience, most hardware stores agree to this.
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Buchsbaum26 Oct 2023 22:10Just use a long spirit level to measure the highest point. This usually determines the required layer thickness. There are self-leveling compounds available for different thicknesses.
You can roughly calculate how much you need—this information is usually on the bags. It’s best to buy a little extra, and as mentioned, you can usually return unused material.
You will also need perimeter insulation strips if the layer is somewhat thicker. As mentioned, the self-leveling compound flows by itself, creating a smooth surface. Since self-leveling compound is relatively expensive, it can be mixed with inexpensive tile adhesive to extend it. I personally never had any issues with this.
It is important to ensure there are no gaps where the compound could leak out, so the edges must be sealed properly.
You can roughly calculate how much you need—this information is usually on the bags. It’s best to buy a little extra, and as mentioned, you can usually return unused material.
You will also need perimeter insulation strips if the layer is somewhat thicker. As mentioned, the self-leveling compound flows by itself, creating a smooth surface. Since self-leveling compound is relatively expensive, it can be mixed with inexpensive tile adhesive to extend it. I personally never had any issues with this.
It is important to ensure there are no gaps where the compound could leak out, so the edges must be sealed properly.
Hello Sahra,
Almost all daily processes can be predicted in advance based on scientific principles.
However, the floor installer will likely deviate from this (theoretically detached) approach and apply their experience when estimating the amount of leveling compound needed.
A preliminary note:
Purchasing the roughly estimated 132.558 kg (about 293 pounds) of leveling compound, to put it humorously at this point, would not be practical.
A better estimate of the expected consumption can be made based on the (to be revised) surface area and a thickness of 5mm (0.2 inches).
Most leveling compounds, due to their almost identical density, can be calculated using 1.2 kg (2.6 pounds) per 1mm (0.04 inches) layer thickness as a basis.
For the 18 m² (about 194 ft²) you specified, we round up to 20 m² (215 ft²) and multiply by 1.2 (density) and 4 (layer thickness in mm).
With 100 kg (220 pounds), you will probably have a sufficient amount with some margin.
At 100 kg, any depressions that need to be filled are likely already included, as I simply assumed a 4mm (0.16 inches) build-up height.
In practice, there should be at least 2mm (0.08 inches), and in living areas, 3 or 4mm (0.12 to 0.16 inches) layer thickness is not a problem.
Any additional costs will be reasonable as long as unused material cannot be returned.
I cannot say whether returns are common at hardware stores. There is always a risk of improper storage (at the customer’s site) that can cause moisture to react with the dry-stored material inside the delivery bags (I have personally encountered this in my professional experience; the floor installer was only unharmed by the process because I could prove that the batch of the leveling compound was already compromised at delivery).
A professional company will be able to use leftover material on another of its construction sites related to the project.
Your question should thus be answered with the value 100.
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Good luck with your project, and please remember the correct, absolutely necessary preparatory work before applying a self-leveling compound on the mineral substrate (at least if the work is meant to be permanent).
Best regards to all: KlaRa
Almost all daily processes can be predicted in advance based on scientific principles.
However, the floor installer will likely deviate from this (theoretically detached) approach and apply their experience when estimating the amount of leveling compound needed.
A preliminary note:
Purchasing the roughly estimated 132.558 kg (about 293 pounds) of leveling compound, to put it humorously at this point, would not be practical.
A better estimate of the expected consumption can be made based on the (to be revised) surface area and a thickness of 5mm (0.2 inches).
Most leveling compounds, due to their almost identical density, can be calculated using 1.2 kg (2.6 pounds) per 1mm (0.04 inches) layer thickness as a basis.
For the 18 m² (about 194 ft²) you specified, we round up to 20 m² (215 ft²) and multiply by 1.2 (density) and 4 (layer thickness in mm).
With 100 kg (220 pounds), you will probably have a sufficient amount with some margin.
At 100 kg, any depressions that need to be filled are likely already included, as I simply assumed a 4mm (0.16 inches) build-up height.
In practice, there should be at least 2mm (0.08 inches), and in living areas, 3 or 4mm (0.12 to 0.16 inches) layer thickness is not a problem.
Any additional costs will be reasonable as long as unused material cannot be returned.
I cannot say whether returns are common at hardware stores. There is always a risk of improper storage (at the customer’s site) that can cause moisture to react with the dry-stored material inside the delivery bags (I have personally encountered this in my professional experience; the floor installer was only unharmed by the process because I could prove that the batch of the leveling compound was already compromised at delivery).
A professional company will be able to use leftover material on another of its construction sites related to the project.
Your question should thus be answered with the value 100.
------------------
Good luck with your project, and please remember the correct, absolutely necessary preparatory work before applying a self-leveling compound on the mineral substrate (at least if the work is meant to be permanent).
Best regards to all: KlaRa
And again from personal experience: we did this about… phew… 25 years ago, but I remember clearly:
First, we had to seal a crack in the screed with epoxy resin and then prime everything with a paste. (Was it black? I don’t remember.)
Then, as DIYers, we mixed large buckets of self-leveling compound one after the other in quick succession: the first batch mixed by two people, the next one by a single person because the other was spreading the compound over 40m² (430ft²) with a trowel. Meanwhile, the next bucket was being prepared, and then applied. Self-leveling compound sets relatively quickly, so you need to work closely together. For 18m² (194ft²) it should be manageable, though.
First, we had to seal a crack in the screed with epoxy resin and then prime everything with a paste. (Was it black? I don’t remember.)
Then, as DIYers, we mixed large buckets of self-leveling compound one after the other in quick succession: the first batch mixed by two people, the next one by a single person because the other was spreading the compound over 40m² (430ft²) with a trowel. Meanwhile, the next bucket was being prepared, and then applied. Self-leveling compound sets relatively quickly, so you need to work closely together. For 18m² (194ft²) it should be manageable, though.
ypg schrieb:
And again from experience: we did this about… phew… 25 years ago, but I clearly remember:
First, we had to fill a crack in the screed with epoxy resin, then prime everything with a paste. (Was it black? I don’t remember anymore.)
Then as DIYers, we stirred up large buckets of leveling compound one after the other in quick succession: the first one mixed by two people, the next one by one person while the other spread the compound over 40 m² (430 ft²) with a trowel. Meanwhile, the next bucket was being prepared, then applied again. Leveling compound sets fairly quickly, so it’s important to work hand in hand. For 18 m² (190 ft²), it should be manageable. I hope that after applying the leveling compound partially, someone took a spiked roller and made sure to release any trapped air from the still-wet compound?
This is an essential part of self-leveling, just like careful substrate preparation!
Best regards, KlaRa
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