Hello everyone,
We have just started renovating our future new home and are planning to install underfloor heating. Since the building dates back to the 1950s, it has a wooden beam ceiling, which is common for that period. When researching the topic, it becomes apparent that using the "standard" liquid screed might cause issues with the structural load (weight) and/or door frame heights (floor buildup height).
Of course, we will consult with qualified professionals about this, but I would be interested to hear how you have approached similar challenges or if you have alternative solution suggestions.
Thank you!
Best regards
We have just started renovating our future new home and are planning to install underfloor heating. Since the building dates back to the 1950s, it has a wooden beam ceiling, which is common for that period. When researching the topic, it becomes apparent that using the "standard" liquid screed might cause issues with the structural load (weight) and/or door frame heights (floor buildup height).
Of course, we will consult with qualified professionals about this, but I would be interested to hear how you have approached similar challenges or if you have alternative solution suggestions.
Thank you!
Best regards
We are slowly approaching the floor construction phase... (as usual, some issues have come up during the demolition that we now need to address, even though they were not originally planned. Since we are doing all the work ourselves, the additional financial expense remains manageable, and time is not a major concern for us.)
No, we raised all the lintels. However, this only affected the first floor, so it was "only" 4 lintels. The mentioned 10-12 cm (4-5 inches) of space applies to the balcony door, which is to remain in place, so that is the limiting factor, but it will definitely be sufficient.
I am now considering another question regarding the floor structure: Our original plan was to level the spaces between the joists with a leveling fill, then install 22mm (7/8 inch) thick OSB panels on which the underfloor heating system (Zewotherm ZEWO Klimaboden) would be laid. To reduce the typical vibrations of a wooden joist ceiling, we intended to fasten the OSB panels to the joists using long screws.
However, a friend advised against screwing the OSB panels down, saying it does not improve vibration properties and actually transmits loud walking noises to the floor below.
His opinion/experience is that vibrations in the ceiling can only be reduced by adding mass, and therefore he would fill the joist cavities with clay or even concrete slabs...
Of course, I understand that with a wooden joist ceiling, some compromises have to be made regarding impact sound and vibrations. Therefore, I would like to hear your experiences and recommendations for a practical floor construction!
Would a two-layer system possibly be more effective (for example, OSB panels screwed to the joists, then an insulation layer to reduce impact sound transmission, and on top of that, floating fermacell screed panels)?
Thank you in advance.
Best regards
11ant schrieb:
Are the door lintels really positioned so high?
No, we raised all the lintels. However, this only affected the first floor, so it was "only" 4 lintels. The mentioned 10-12 cm (4-5 inches) of space applies to the balcony door, which is to remain in place, so that is the limiting factor, but it will definitely be sufficient.
I am now considering another question regarding the floor structure: Our original plan was to level the spaces between the joists with a leveling fill, then install 22mm (7/8 inch) thick OSB panels on which the underfloor heating system (Zewotherm ZEWO Klimaboden) would be laid. To reduce the typical vibrations of a wooden joist ceiling, we intended to fasten the OSB panels to the joists using long screws.
However, a friend advised against screwing the OSB panels down, saying it does not improve vibration properties and actually transmits loud walking noises to the floor below.
His opinion/experience is that vibrations in the ceiling can only be reduced by adding mass, and therefore he would fill the joist cavities with clay or even concrete slabs...
Of course, I understand that with a wooden joist ceiling, some compromises have to be made regarding impact sound and vibrations. Therefore, I would like to hear your experiences and recommendations for a practical floor construction!
Would a two-layer system possibly be more effective (for example, OSB panels screwed to the joists, then an insulation layer to reduce impact sound transmission, and on top of that, floating fermacell screed panels)?
Thank you in advance.
Best regards
ShawN46 schrieb:
His opinion/experience is that the vibrations of the ceiling can only be reduced by adding more mass, so he would fill the spaces between the joists with clay or even concrete slabs...And what is supposed to support this immense weight?Vibrations are reduced by resilient mounting. I often get the impression in this forum that impact sound is thought of as the same as airborne sound, just with a different direction of radiation. However, impact sound is not a secondary vibration transmitted through the air to a component. It is mechanically generated at the moment of impact. To damp it out with mass or stiffness requires a completely different approach (more precisely: an inappropriate one, as in this suggestion).
I would rather look for a solution by dissipating the “impact energy” and avoiding rigid connections between components and their installation.
Heavy materials do not belong in the spaces between the joists but on top of them. Again, it seems to me that the wood joist ceiling is being imagined essentially as a horizontally installed prefabricated wall.
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Hello questioner.
I’m honored, of course, that you value my opinion!
Regarding Part 1: leveling the height
A leveling screed is always used for surface leveling. For example, when the subfloor is very uneven or the allowable angle deviation limits are exceeded. In that case, the floor is “crooked.”
However, when dealing with exposed joists that do not meet these flatness requirements, a different approach is needed. Here, the future load distribution layer (floorboards, OSB, or wood chipboard panels) must be leveled precisely. This can only be achieved by first measuring the height of the joist layer and then shimming with cut wooden wedges glued onto the joists (!!).
A 22mm (7/8 inch) OSB panel installation, on which the Zewotherm insulation board is placed, can definitely be a workable solution.
Part 2: the load distribution layer
The thickness of the floorboards or OSB panels mainly depends on the spacing of the joists. At a joist spacing of 45cm/50cm (18 inches/20 inches), a thickness of 22mm (7/8 inch) is usually sufficient. Otherwise, they will bend too much under load.
(Quote) “To reduce the typical vibrations of a wooden joist ceiling, we wanted to fasten the OSB panels to the joists with long screws.”
Answer: Better not do that!
For joists leveled in height, we attach thick fleece strips with adhesive bead underneath (or better: stapled) on which the OSB panels rest loosely. Otherwise, the screws will create sound bridges “on a silver platter” into the building.
It is true that in timber construction one has to accept that optimal impact sound insulation is not achievable.
Part 3: sound insulation between the timber framing
Concrete panels between the framing members? Well, I leave that open to common-sense evaluation.
Theoretically, that might work, but practically it is impossible to achieve!
The spaces between the framing should actually be filled with dry, dust-free mineral materials with high density. Building material suppliers will certainly offer suitable products for this.
A two-layer design is always better than a single layer, but this depends on the available construction height.
In that case, one could lay 19mm (3/4 inch) panels on the joists, then mineral wool impact sound insulation (ideal for timber construction), and then 22mm (7/8 inch) OSB panels with the underfloor heating system’s specific panel on top.
The thinner the upper load distribution layer, the more it will resonate.
For example, no drummer would want to play on very thick drumheads. Only thin membranes resonate well—just like thin gypsum fiberboards.
--------------------
I hope I was able to shed some light on the matter!
Regards, KlaRa
I’m honored, of course, that you value my opinion!
Regarding Part 1: leveling the height
A leveling screed is always used for surface leveling. For example, when the subfloor is very uneven or the allowable angle deviation limits are exceeded. In that case, the floor is “crooked.”
However, when dealing with exposed joists that do not meet these flatness requirements, a different approach is needed. Here, the future load distribution layer (floorboards, OSB, or wood chipboard panels) must be leveled precisely. This can only be achieved by first measuring the height of the joist layer and then shimming with cut wooden wedges glued onto the joists (!!).
A 22mm (7/8 inch) OSB panel installation, on which the Zewotherm insulation board is placed, can definitely be a workable solution.
Part 2: the load distribution layer
The thickness of the floorboards or OSB panels mainly depends on the spacing of the joists. At a joist spacing of 45cm/50cm (18 inches/20 inches), a thickness of 22mm (7/8 inch) is usually sufficient. Otherwise, they will bend too much under load.
(Quote) “To reduce the typical vibrations of a wooden joist ceiling, we wanted to fasten the OSB panels to the joists with long screws.”
Answer: Better not do that!
For joists leveled in height, we attach thick fleece strips with adhesive bead underneath (or better: stapled) on which the OSB panels rest loosely. Otherwise, the screws will create sound bridges “on a silver platter” into the building.
It is true that in timber construction one has to accept that optimal impact sound insulation is not achievable.
Part 3: sound insulation between the timber framing
Concrete panels between the framing members? Well, I leave that open to common-sense evaluation.
Theoretically, that might work, but practically it is impossible to achieve!
The spaces between the framing should actually be filled with dry, dust-free mineral materials with high density. Building material suppliers will certainly offer suitable products for this.
A two-layer design is always better than a single layer, but this depends on the available construction height.
In that case, one could lay 19mm (3/4 inch) panels on the joists, then mineral wool impact sound insulation (ideal for timber construction), and then 22mm (7/8 inch) OSB panels with the underfloor heating system’s specific panel on top.
The thinner the upper load distribution layer, the more it will resonate.
For example, no drummer would want to play on very thick drumheads. Only thin membranes resonate well—just like thin gypsum fiberboards.
--------------------
I hope I was able to shed some light on the matter!
Regards, KlaRa
A
Altbau19305 Jun 2017 12:30Thank you for your detailed and knowledgeable explanation, KlaRa!
We also want to install a bathroom in one of the now "standard" rooms of our 1930s house, which has wooden ceilings.
How many centimeters (inches) will the floor height increase in the end with tiles, if I build everything properly above the joists and waterproof it?
For such projects, you always have to consider door heights and lintels.
We also want to install a bathroom in one of the now "standard" rooms of our 1930s house, which has wooden ceilings.
How many centimeters (inches) will the floor height increase in the end with tiles, if I build everything properly above the joists and waterproof it?
For such projects, you always have to consider door heights and lintels.
Hello unknown questioner.
Primarily, this question should be addressed to a structural engineer to determine what load can actually be supported given the beam dimensions.
I am not mentioning this without reason; this must (!!) be clarified beforehand.
Without considering the wedge-shaped shims used for height alignment, the load-distribution layer (on the joists) will require 19mm (3/4 inch). On top of this, a mineral wool insulation layer, e.g., "Floorrock GP," with 30mm (1 1/4 inch) thickness (total: 49mm (2 inches)), followed by a 22mm (7/8 inch) OSB board as the load-distribution layer (total: 71mm (2 3/4 inches)) + alternative waterproofing + tile adhesive + tiles = 15mm (5/8 inch), resulting in a total build-up height of approximately 86mm (3 3/8 inches).
You could save some height only by reducing the impact sound insulation from 30mm (1 1/4 inch) to 20mm (3/4 inch), which would of course compromise impact sound protection.
Considering the build-up roughly, a total thickness between 80 and 95mm (3 1/8 to 3 3/4 inches) will always be required!
------------------
Greetings from the desk
KlaRa
Primarily, this question should be addressed to a structural engineer to determine what load can actually be supported given the beam dimensions.
I am not mentioning this without reason; this must (!!) be clarified beforehand.
Without considering the wedge-shaped shims used for height alignment, the load-distribution layer (on the joists) will require 19mm (3/4 inch). On top of this, a mineral wool insulation layer, e.g., "Floorrock GP," with 30mm (1 1/4 inch) thickness (total: 49mm (2 inches)), followed by a 22mm (7/8 inch) OSB board as the load-distribution layer (total: 71mm (2 3/4 inches)) + alternative waterproofing + tile adhesive + tiles = 15mm (5/8 inch), resulting in a total build-up height of approximately 86mm (3 3/8 inches).
You could save some height only by reducing the impact sound insulation from 30mm (1 1/4 inch) to 20mm (3/4 inch), which would of course compromise impact sound protection.
Considering the build-up roughly, a total thickness between 80 and 95mm (3 1/8 to 3 3/4 inches) will always be required!
------------------
Greetings from the desk
KlaRa
Hello KlaRa,
first of all, thank you again for your detailed explanation(s)!
On the ground floor, the floor consists of hollow bricks placed between steel T-beams. In the past, wooden beams (referred to as “sleepers” in the building description) were laid and fixed over these T-beams to distribute the load.
Now that we have removed the entire floor structure, we are considering what kind of new load distribution layer would be appropriate so that the hollow bricks do not have to carry any load.
We plan to fill the spaces between the T-beams with leveling fill and then install screed boards with a thickness of 30mm (1.2 inches) plus 10mm (0.4 inches) of wood fiber insulation underneath for thermal insulation toward the basement.
The question is whether this would be suitable as a load distribution layer?
Thank you in advance!
Best regards and enjoy the rest of the weekend
first of all, thank you again for your detailed explanation(s)!
On the ground floor, the floor consists of hollow bricks placed between steel T-beams. In the past, wooden beams (referred to as “sleepers” in the building description) were laid and fixed over these T-beams to distribute the load.
Now that we have removed the entire floor structure, we are considering what kind of new load distribution layer would be appropriate so that the hollow bricks do not have to carry any load.
We plan to fill the spaces between the T-beams with leveling fill and then install screed boards with a thickness of 30mm (1.2 inches) plus 10mm (0.4 inches) of wood fiber insulation underneath for thermal insulation toward the basement.
The question is whether this would be suitable as a load distribution layer?
Thank you in advance!
Best regards and enjoy the rest of the weekend
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