ᐅ Adding an Additional Floor. Use the Same Brick as the Ground Floor? Insulation of the Existing Structure?
Created on: 11 Oct 2016 14:35
H
HausbauWI2016
Hello,
I am planning to add a story to an L-shaped bungalow next year. The house has a full basement, and both the basement walls and the ground floor are built with solid pumice concrete blocks. Initially, the plan was to raise the existing hip roof, build an upper floor, and then reattach the roof. However, since the roof was originally constructed with narrow rafters and is not insulated, I was advised to remove it entirely and install a new double-pitched roof with thicker rafters and insulation.
Now, some questions. The architect suggested using 24 cm (9.5 inches) calcium silicate blocks with 10 to 12 cm (4 to 5 inches) external thermal insulation made of polystyrene.
I mentioned that there is a lot of negative feedback about external thermal insulation systems and that the additional costs only pay off after a long time. The architect responded that the savings on calcium silicate blocks balance out the cost of insulation, so calcium silicate plus external thermal insulation equals the price of a well-insulated solid block.
For aesthetic reasons, the upper floor should not overhang the ground floor, so external insulation would also have to be applied to the existing ground floor walls. Is this advisable? The architect said that since exterior work is necessary anyway, the extra cost for insulating the ground floor would be only around 15,000 EUR.
When I consulted a construction company and a structural engineer, both advised against using calcium silicate blocks and recommended 24 cm (9.5 inches) pumice blocks, like the existing structure. Both also recommend full external thermal insulation.
On the other hand, I have read and seen that construction company owners and similar professionals rarely equip their own homes with façade insulation. However, the builder I spoke to showed me the insulation on his own house — he uses external thermal insulation. What is really recommended? Supposedly, over 90% of new buildings have external insulation.
Regarding the type of block, pumice and calcium silicate are similar in price. Pumice offers better thermal retention but transmits sound more easily, while calcium silicate blocks sound better but are colder.
I would truly appreciate any advice and tips.
I am planning to add a story to an L-shaped bungalow next year. The house has a full basement, and both the basement walls and the ground floor are built with solid pumice concrete blocks. Initially, the plan was to raise the existing hip roof, build an upper floor, and then reattach the roof. However, since the roof was originally constructed with narrow rafters and is not insulated, I was advised to remove it entirely and install a new double-pitched roof with thicker rafters and insulation.
Now, some questions. The architect suggested using 24 cm (9.5 inches) calcium silicate blocks with 10 to 12 cm (4 to 5 inches) external thermal insulation made of polystyrene.
I mentioned that there is a lot of negative feedback about external thermal insulation systems and that the additional costs only pay off after a long time. The architect responded that the savings on calcium silicate blocks balance out the cost of insulation, so calcium silicate plus external thermal insulation equals the price of a well-insulated solid block.
For aesthetic reasons, the upper floor should not overhang the ground floor, so external insulation would also have to be applied to the existing ground floor walls. Is this advisable? The architect said that since exterior work is necessary anyway, the extra cost for insulating the ground floor would be only around 15,000 EUR.
When I consulted a construction company and a structural engineer, both advised against using calcium silicate blocks and recommended 24 cm (9.5 inches) pumice blocks, like the existing structure. Both also recommend full external thermal insulation.
On the other hand, I have read and seen that construction company owners and similar professionals rarely equip their own homes with façade insulation. However, the builder I spoke to showed me the insulation on his own house — he uses external thermal insulation. What is really recommended? Supposedly, over 90% of new buildings have external insulation.
Regarding the type of block, pumice and calcium silicate are similar in price. Pumice offers better thermal retention but transmits sound more easily, while calcium silicate blocks sound better but are colder.
I would truly appreciate any advice and tips.
B
Bauexperte13 Oct 2016 23:26HausbauWI2016 schrieb:
When I talked to a construction company and a structural engineer, both advised me not to use sand-lime brick, but rather a 24cm (9.5 inches) pumice block, as in the existing structure. Both also recommended full thermal insulation. I would also recommend pumice and—typical for me 😀—external insulation on the facade; it doesn’t necessarily have to be an external thermal insulation composite system (ETICS).
Besides the fact that pumice is a natural building material, it doesn’t make much sense in my opinion to create mixed masonry, especially since pumice and sand-lime brick have opposite advantages. Since you have to apply insulation anyway, soundproofing—given the final overall wall thickness—becomes irrelevant.
Best regards, Bauexperte
H
HausbauWI201614 Oct 2016 08:24Ok, thanks, that already gives some direction. So you clearly recommend pumice? Although sand-lime brick is also a natural stone. I was told that pumice walls feel warmer. Unfortunately, I can’t check this at the house because the walls are covered with drywall. In your opinion, is 10 cm (4 inches) of insulation sufficient? I want to avoid making the window reveal too deep.
B
Bauexperte14 Oct 2016 09:12HausbauWI2016 schrieb:
So you are clearly recommending pumice concrete? Yes, I tend to side more with the structural engineer than with the architect; it’s definitely safer in the long run. Besides, pumice concrete is, in my view, a good—even if underrated—building material, and I don’t see any logical reason to deviate from it.
HausbauWI2016 schrieb:
Do you think 10cm (5 inches) of insulation is sufficient? I want to avoid having the window reveals become too deep. Answering that would be negligent; it has to be calculated specifically for the individual project!
For example, we insulated under the roof with a thermal conductivity rating of 0.032 W/(m·K) (out of necessity, as we didn’t want to increase the thickness of the rafters at the expense of the living space below), and naturally the building envelope receives a suitable 120mm (4.7 inches) insulation layer.
Regards, Bauexperte
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