ᐅ Is it acceptable to tolerate parquet flooring with many hollow spots after 4 months?

Hello,

This concerns a building from 1973. The original screed is still in place. The ceiling construction consists of 30cm (12 inches) of reinforced concrete, 2cm (0.8 inches) of polystyrene insulation, and on top of that the screed, which is 4-8cm (1.5-3 inches) thick. At the time, I thought the screed should be replaced because it was heavily sandy and partially crumbling from underneath. I also found it very uneven, although within acceptable tolerances. The professionals advised against replacement, saying that priming and filling would be sufficient.

After the filling, about 20 square meters (215 square feet) of bamboo parquet were fully glued down. There were gaps between the boards of up to 2mm (0.08 inches). As a result, the parquet was removed, the surface was re-filled, and the flooring was reinstalled.

Since February, approximately 100 of 140 square meters (1,070 of 1,500 square feet) have been installed. Only a few spots have gaps that exceed tolerance. This is acceptable to me.

The living room had to wait due to delays with the fireplace. We now live in the house, and while walking, I repeatedly notice hollow spots under the parquet. However, there is no movement of the floor itself; it simply sounds hollow when I walk over it. I have identified this in eight locations so far.

I believe the issue is related to the old screed. I suspect the filler is separating from the screed, creating hollow areas due to the uneven floor. Alternatively, there may be voids within the screed itself that cause the hollow sound.

According to the contractors, this is normal and something I have to accept.

I would appreciate a neutral opinion from you. Do I really have to accept this?

Best regards,

Adrian

dugolino schrieb:

Hello,

This concerns a building from 1973. The original screed is still in place. Ceiling construction: 30cm (12 inches) reinforced concrete, 2cm (0.8 inches) polystyrene insulation, and on top of that, the screed with a thickness of 4-8cm (1.6-3.1 inches). At the time, I believed it should be replaced because it was very sandy and had broken away in some places from underneath. Additionally, I found it quite uneven, though still within tolerance limits. The experts advised against replacing it back then, saying that priming and leveling would be sufficient.

After the leveling compound was applied, the first 20 square meters (215 square feet) of bamboo parquet were fully glued down. There were gaps of up to 2mm (0.08 inches) between the planks. As a result, the flooring was removed, the surface re-leveled, and the parquet reinstalled.

Since February, about 100 of the 140 square meters (1,507 square feet) have been installed. Only a few spots have gaps beyond the acceptable tolerance. To me, this is acceptable.

The living room installation had to wait due to delays with the fireplace. We already live in the house, and when walking, I consistently notice hollow spots under the parquet. However, there is no perceptible movement of the floor; it just sounds hollow when I walk over it. I have identified this in eight locations so far.

I believe the problem stems from the old screed. I suspect that the leveling compound is detaching from the screed, creating hollow areas because of the uneven substrate. Alternatively, there may be voids within the screed itself, which produce the hollow sound.

According to the craftsmen, this is normal, and I have to live with it.

I would appreciate a neutral opinion from you. Do I really have to accept this?

Best regards,

Adrian

In addition, it makes sense to always involve the appropriate specialist @KlaRa and to provide some photos, preferably also from the construction phase, such as the original condition, leveling work, etc.

Thanks to i_b_n_a_n for the kind words!
@ "dugolino":
Basically, as my first statement, it is not always possible to install parquet strips or (more generally) parquet elements without any voids underneath! However, it must be taken into account that this is due to the fact that the "usual surface flatness" of screeds, especially with large (or larger) floor elements, prevents full-surface support at the back on the screed (or better: leveling compound).

Now comes my second statement:
The above remark only applies to small-area hollow spots beneath a parquet floor. The comment in DIN 18356 "Parquet and wood block flooring works" considers a minimum of 60% adhesion area as the lower limit for sufficient bonding. Parquet elements with hollow spots must also not "rock" when walked upon or produce creaking sounds.
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The question about the cause of larger-area hollow spots can only be answered by the parquet itself, as I like to say. To do this, the parquet must be "examined" by opening it up and inspecting the fracture zone on the back side. Therefore, the request from i_b_n_a_n for photos is justified, especially if the situation is to be assessed from a distance. Important are
a) the location of the fracture zone in the screed and
b) how the back side of the hollow parquet floor looks.
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Best regards, KlaRa

Thank you very much for the detailed answers. I think I will open up the worst hollow spot for me and take plenty of pictures. This hollow spot can then be filled right away, solving the problem here. I will get back to you soon with pictures.

Best regards,
Adrian

Hello Adrian.
Before you have anything opened:
Make a sketch of the affected room and, as accurately to scale as possible, mark the locations and extent of the hollow spaces within it!!