Work on basement ceiling insulation with stone wool

Hello. I have a house. Fully basemented. Currently no insulation on it, so the boards are directly visible. Now I have received several rock wool boards with a thickness of 60mm as a gift. These boards have a somewhat firmer white material on both sides to glue the boards directly to the ceiling. The problem is the ceiling height. The 60mm are too thick for me. I would have to cut the boards in half in the middle, so to 30mm. So that you can still walk at all. (unfortunately extremely low ceiling height) After cutting them in half, however, this white layer would be gone, so I would have to glue the rock wool directly to the ceiling. I would cut them in half with a pruning saw with good guidance so that the sawn surface remains even. Does anyone have experience if that would be possible? Best regards Herbert

Halving should generally be possible; they can also be cut crosswise and glued. The prepared surface will then be lost, so I would additionally dowel it to ensure stability. What year was the house built, or do you have any knowledge about the existing screed? For anything from 1978 onwards, I wouldn’t worry about an additional 3 cm of insulation from below. In older buildings with only 0-2 cm of insulation thickness (of which little remains after 40+ years), that can help, but 6 cm is naturally better.

Hello, thanks for the message.

So the house is from 1950. There are metal beams visible from below with concrete slabs laid in between. So the surface is anything but even.

On the ground floor there is underfloor heating with tiles. In the middle of winter you can comfortably sit in the basement with a sweater on. That’s why I wanted to insulate from below. The basement is also quite damp. The basement walls are made of natural stones. So large granite rubble stones with a lot of sand/a bit of cement mixture. (but the house holds). Because of the moisture I didn’t want Styrofoam boards, otherwise the water might condense even more? Maybe someone has experience with the moisture there. So all ceilings are currently covered with wooden panels. But there is no mold on the ceiling. So it’s not that wet after all. Best regards Herbert

Due to the moisture, I didn't want Styrofoam panels, otherwise the water would still condense? Maybe someone also has experience with moisture regarding this.

Regarding ceiling insulation under a concrete ceiling, you don't need to worry about moisture. No vapor comes through from "above" through the concrete ceiling and none enters from below either, because the ceiling is warm compared to the other walls/floor, especially with underfloor heating. EPS as "Styrofoam" would not have a higher thermal resistance than mineral wool. Only PUR / PIR would have a somewhat greater effect, but 1. is significantly more expensive and 2. only has fire protection class B, so it may not be used or only under certain conditions in garages with car parking spaces and rooms with gas- or oil-powered heating systems. Therefore: mineral wool is indeed the best solution, especially if it is available for free. With underfloor heating, I would however make sure to use the full thickness as much as possible over a large area. Heat loss through the underfloor heating areas is twice as high as over unheated areas.

So all ceilings are currently covered with wooden panels. However, there is no mold on the ceiling.

The basement ceiling? Then remove the paneling and install the insulation. The paneling is usually also attached to a substructure, so that probably 4-5 cm thickness is achieved there anyway.

The problem is the ceiling height. The 60mm is too thick for me. I would have to halve the panels in the middle, so to 30mm. Just so you can still walk at all. (unfortunately extremely low ceiling height)

If 3cm decide between walking and not walking, in my opinion the perception is somewhat distorted. Please stick the 60mm ones on and enjoy an insulated floor - and don't annoy yourself about having to (how often actually?) bend over. In my opinion, the installation will also be really tough, as you have to press the panels against the ceiling, which will not work so well if halved.

Thank you very much for the first answers. I see it the same way, free insulation and it cannot burn. What more could I want.

The basement ceiling? Then remove the cladding and install the insulation. The cladding is usually also attached to a substructure, so that probably 4-5 cm thickness can be achieved there anyway.

Yes, due to the uneven ceiling there is a load-bearing batten and cross batten. Then the wooden panels on top. The wood should also be reattached, that was the first idea. Sparing the two battens is definitely a huge effort. But for a rustic basement bar, it belongs back there. I have to think about it. Wood certainly also has good thermal insulation value. So then the insulation around the first batten. Then cut out again crosswise. It would be better to leave it white...

Are there special dowels and adhesives for the insulation boards? Has anyone had good experience with a manufacturer and type? I have attached a picture of the type of insulation.

Best regards, Herbert