majestix
2013-05-19 19:21:48
- #1
Hello everyone, we are building a single-family house (approx. 123sqm living space, 1.5 floors, without a basement) and started the week before last.
Here is the situation:
I am doing the shell construction together with my friend, who is a master mason and does good work. However, yesterday during the excavation of the foundations, we made a mistake, which only became apparent when measuring the sewer connections inside the house.
The surveyor marked out the external dimensions including 16cm WDVS during the fine staking.
According to the system section of the structural engineer, however, the 24cm external masonry is flush with the foundation slab. This means that the dimensions of the foundation slab would have to be 8.11m x 9.68m.
That means we should have subtracted 16cm for the WDVS from the surveyor’s marked dimensions before the foundations begin. But we took the surveyor’s measurement for the strip foundations and now the foundation slab would have dimensions of 8.43 x 10m. So about 32cm more on each side.
My friend proposed the following:
We will do a 6mm external insulation (instead of 4mm) on the strip foundations (80cm, unreinforced) and leave out the internal insulation (4mm). This would give the foundation about 2mm more bearing surface for the concrete.
(Regarding the internal insulation, he had already suggested leaving it out because we insulate the foundations down to the ground. The foundation slab itself is planned with 20cm Lava 16/32, 10cm clean layer, 10cm insulation and 25cm foundation slab. The foundation slab is about 50cm above ground level.)
He said that the WDVS would then be flush with the foundations.
My questions to you are as follows:
In the current situation, I could then offset the masonry by about 4cm more to the outside with only 12cm WDVS. This would give us a bit more living space. The only problem I see here is that, compared to the plan, we would have different internal dimensions and, for example, also a somewhat larger span for the floor slab.
Of course, I don’t want to make a mountain out of a molehill if it’s just a minor issue. There are DIN standards and other rules, and there is a reasonable weighing of factors. I would like that from you and how you would do it as a builder, professional or structural engineer?
Here is the situation:
I am doing the shell construction together with my friend, who is a master mason and does good work. However, yesterday during the excavation of the foundations, we made a mistake, which only became apparent when measuring the sewer connections inside the house.
The surveyor marked out the external dimensions including 16cm WDVS during the fine staking.
According to the system section of the structural engineer, however, the 24cm external masonry is flush with the foundation slab. This means that the dimensions of the foundation slab would have to be 8.11m x 9.68m.
That means we should have subtracted 16cm for the WDVS from the surveyor’s marked dimensions before the foundations begin. But we took the surveyor’s measurement for the strip foundations and now the foundation slab would have dimensions of 8.43 x 10m. So about 32cm more on each side.
My friend proposed the following:
We will do a 6mm external insulation (instead of 4mm) on the strip foundations (80cm, unreinforced) and leave out the internal insulation (4mm). This would give the foundation about 2mm more bearing surface for the concrete.
(Regarding the internal insulation, he had already suggested leaving it out because we insulate the foundations down to the ground. The foundation slab itself is planned with 20cm Lava 16/32, 10cm clean layer, 10cm insulation and 25cm foundation slab. The foundation slab is about 50cm above ground level.)
He said that the WDVS would then be flush with the foundations.
My questions to you are as follows:
[*]The external dimensions do not change, so we still comply with the setback areas, right?
[*]Do you see a problem with the foundation slab being flush with the external WDVS dimensions?
[*]The foundation slab is now about 5sqm larger. Do you see a structural problem here or is this within tolerance?
[*]We had already considered taking a simple BIMS thermal insulation block of for example 0.12 or 0.13 (instead of 0.16) and maybe reducing the WDVS from 16cm to about 12cm or 10cm.
In the current situation, I could then offset the masonry by about 4cm more to the outside with only 12cm WDVS. This would give us a bit more living space. The only problem I see here is that, compared to the plan, we would have different internal dimensions and, for example, also a somewhat larger span for the floor slab.
[*]Is this still permissible under building law (approval exemption according to §67 Building Code)?
[*]Structural engineering within tolerance or not?
Of course, I don’t want to make a mountain out of a molehill if it’s just a minor issue. There are DIN standards and other rules, and there is a reasonable weighing of factors. I would like that from you and how you would do it as a builder, professional or structural engineer?