ᐅ Soil report for a 140 sqm bungalow – additional costs for waterproof concrete?
Created on: 8 Sep 2022 10:41
E
EinmalimLeben
Hello!
This is my first time writing in the forum, and I’ll briefly introduce what we are planning/building:
- Bungalow with solid construction, 140 sqm (1,507 sq ft), without a basement, developer-built, building site in Lower Saxony, contract already signed and planned with the architect from the construction company.
Currently, we are preparing the building permit/planning permission application and have the soil report available. Therefore, we need waterproof concrete (WU concrete), and our developer estimates about 130 euros per sqm (square meter) of the house’s external dimensions; the final price can only be calculated after the structural engineering and material selection phase.
My questions: is there an alternative to WU concrete? Is this the same as a “white tank” (waterproof concrete structure)? I thought this wouldn’t be necessary since we are building without a basement? Is the cost estimate realistic, or what are your calculations? Since we are building to KfW40 energy standards, insulation is required—what additional costs should we expect approximately?
Thanks for your help!
This is my first time writing in the forum, and I’ll briefly introduce what we are planning/building:
- Bungalow with solid construction, 140 sqm (1,507 sq ft), without a basement, developer-built, building site in Lower Saxony, contract already signed and planned with the architect from the construction company.
Currently, we are preparing the building permit/planning permission application and have the soil report available. Therefore, we need waterproof concrete (WU concrete), and our developer estimates about 130 euros per sqm (square meter) of the house’s external dimensions; the final price can only be calculated after the structural engineering and material selection phase.
My questions: is there an alternative to WU concrete? Is this the same as a “white tank” (waterproof concrete structure)? I thought this wouldn’t be necessary since we are building without a basement? Is the cost estimate realistic, or what are your calculations? Since we are building to KfW40 energy standards, insulation is required—what additional costs should we expect approximately?
Thanks for your help!
E
EinmalimLeben16 Sep 2022 05:27Sure, no problem! I’m happy to help! I also wanted to send you a private message, but I’m not authorized yet. 🙂
I also find it problematic that we have to ask. I don’t want to imply anything, but it’s at least a bit “strange”... We did a bit more detailed checking and received the invoice today. It was also “overlooked” that we didn’t want the standard HW front door, for example, and this needs to be deducted. Another 1,000. So, as always with building: check and question everything...
We agreed with the soil surveyor that he would examine the topsoil at the same time, so we’ll know what we can do with the soil. Basically, it’s about 200 m3 (260 cubic yards), which is somewhat too much for our 700 sqm (7,535 sq ft) plot.
I also find it problematic that we have to ask. I don’t want to imply anything, but it’s at least a bit “strange”... We did a bit more detailed checking and received the invoice today. It was also “overlooked” that we didn’t want the standard HW front door, for example, and this needs to be deducted. Another 1,000. So, as always with building: check and question everything...
We agreed with the soil surveyor that he would examine the topsoil at the same time, so we’ll know what we can do with the soil. Basically, it’s about 200 m3 (260 cubic yards), which is somewhat too much for our 700 sqm (7,535 sq ft) plot.
I have been curious about how this outrageous additional cost for waterproof concrete (WU) actually comes about.
I had a 220m2 (2,368 sq ft) concrete slab, with 45m3 (1,590 cubic feet) of ready-mix concrete.
I thought the surcharge for waterproof concrete was around €1 per m3 (about $1.10 per cubic yard)?
So, that would be about €45 (around $50)?
I remember paying about €4,500 gross (around $4,900) with a large concrete pump. That was two years ago.
@Cronos86 or am I mixing something up here?
I had a 220m2 (2,368 sq ft) concrete slab, with 45m3 (1,590 cubic feet) of ready-mix concrete.
I thought the surcharge for waterproof concrete was around €1 per m3 (about $1.10 per cubic yard)?
So, that would be about €45 (around $50)?
I remember paying about €4,500 gross (around $4,900) with a large concrete pump. That was two years ago.
@Cronos86 or am I mixing something up here?
P
Pitiglianio16 Sep 2022 09:14Additional cost for waterproof foundation slab was 1885 euros for me. 85m² (915 sq ft), 25cm (10 inches) thick. General contractor’s offer from early 2022.
Unfortunately, I can’t say much about the general prices and specifications. However, the cost of concrete is only part of the total additional expenses. Regular C 25/30 concrete costs around €100 per m³ (about $100 per cubic yard), and for the waterproof (WU) version, it rises to €125 to €150 per m³ (about $125 to $150 per cubic yard) — very roughly, and I’m not sure how prices are currently changing.
Additionally, as mentioned by the home builder: a slab at least 25cm (10 inches) thick, more reinforcement steel, and possibly a new structural calculation?
Then there’s increased effort with penetrations regarding waterproofing. All of this brings quite a chain reaction of further tasks.
I also find the €131 per m² (about $12 per square foot) extra cost to be quite high, but I was already aware that this type of waterproofing leads to significant additional expenses.
Good decision.
Additionally, as mentioned by the home builder: a slab at least 25cm (10 inches) thick, more reinforcement steel, and possibly a new structural calculation?
Then there’s increased effort with penetrations regarding waterproofing. All of this brings quite a chain reaction of further tasks.
I also find the €131 per m² (about $12 per square foot) extra cost to be quite high, but I was already aware that this type of waterproofing leads to significant additional expenses.
EinmalimLeben schrieb:
We have agreed with the soil expert that he will analyze the topsoil right away, so we will know what we can do with the soil. Basically, it’s about 200 m³ (260 cubic yards) and a bit too much for our 700m² (7,535 square feet) lot.
Good decision.
E
EinmalimLeben19 Sep 2022 17:49So, I spoke today with the contact person at the water utility, who had been on vacation. Basically, drainage is allowed. He explained that the water is collected in a container filled with sand and then directed to the rainwater system. We have to take care of cleaning this container ourselves. He then connected me to the wastewater contact. This person also confirmed that drainage is tolerated. I need to submit an application along with the connection, and there is a surface area calculation form that is important. He recommended that we do both: waterproofing (WU) and drainage. This, of course, has caused us some confusion again.
We are now waiting for the revision of the expert report and will then have everything in black and white regarding the warranty. Correct?
We are now waiting for the revision of the expert report and will then have everything in black and white regarding the warranty. Correct?
So, the geotechnical engineer guarantees that a drainage system is feasible. However, no one can guarantee that the drainage will function permanently. Anything can happen... like a tree root growing in and clogging the drain, for example.
But to reassure you, what exactly could go wrong? As I already mentioned, nothing can get underneath the house because of the strip foundations. So, it’s only about the outer edge. Usually, the surface is shaped so that rainwater flows away from the house. There would have to be standing water right next to the house, and for some time as well. And if the drainage pipe were blocked, you still have a gravel trench with a slope around the pipe that channels the water away.
So, unless you live on a slope where streams of surface water flow directly toward your house and splash onto the slab from above, it should work fine.
Regards
But to reassure you, what exactly could go wrong? As I already mentioned, nothing can get underneath the house because of the strip foundations. So, it’s only about the outer edge. Usually, the surface is shaped so that rainwater flows away from the house. There would have to be standing water right next to the house, and for some time as well. And if the drainage pipe were blocked, you still have a gravel trench with a slope around the pipe that channels the water away.
So, unless you live on a slope where streams of surface water flow directly toward your house and splash onto the slab from above, it should work fine.
Regards
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