ᐅ Basement originally partially constructed with concrete, now possibly fully built with masonry.
Created on: 19 Jan 2017 00:04
K
Kaspatoo
Hi,
In previous discussions and offers, we agreed with our provider (architect/owner of the construction company, including their own site, excavator, employees, etc.) to build the basement roughly half in 24cm (10 inches) thick concrete and the other half with masonry.
The background is that we have a sloped site, and the basement is about half above ground level, containing two living rooms. The rooms at the rear, towards the slope, are a heating room, storage room, and bathroom.
We do not have a soil report. The soil is clay/loam-like (my father-in-law called it red marl). So, it is not very permeable. Above us runs the road, and beyond that, the slope continues for about 50-100m (55-110 yards), then you reach the top of the hill. Two more plots will be developed above us. The house and road are roughly at the same level (plus a step).
We now want to finalize the contract details. The architect recently called me and said he would prefer to build the entire basement with masonry (thickness unknown but thicker than 24cm (10 inches)), including drainage. The drainage would not clog because it would be in a gravel bed.
I have researched and, as expected, I am uncertain about which option is better and what questions I should ask the architect or what details should be agreed upon.
Basically, there are two methods: waterproof concrete (often called a white tank) and sealing with bitumen or plastic membranes (often called a black tank).
Regarding the cost of both options, I have read very different statements; for some, one was more expensive, for others, the other was. Or it was previously like that, but now they say the costs are about the same. The waterproof concrete method is said to be much more common nowadays.
I also found, but only from one source (other sites had exactly the same text), that bitumen variants last only about 30 years, while waterproof concrete easily lasts 80 years. Is there any truth to this? Has anyone had to remove their soil because water appeared after 30 years?
Back to the upcoming discussion with the architect. Should he provide a written guarantee of watertightness? Is the concrete method definitely waterproof and generally requires less long-term warranty? What else should I pay attention to (I won’t sign immediately, but a more confident approach wouldn’t hurt)? What might be a rough but reasonable wording for both options in the contract?
Thank you very much.
In previous discussions and offers, we agreed with our provider (architect/owner of the construction company, including their own site, excavator, employees, etc.) to build the basement roughly half in 24cm (10 inches) thick concrete and the other half with masonry.
The background is that we have a sloped site, and the basement is about half above ground level, containing two living rooms. The rooms at the rear, towards the slope, are a heating room, storage room, and bathroom.
We do not have a soil report. The soil is clay/loam-like (my father-in-law called it red marl). So, it is not very permeable. Above us runs the road, and beyond that, the slope continues for about 50-100m (55-110 yards), then you reach the top of the hill. Two more plots will be developed above us. The house and road are roughly at the same level (plus a step).
We now want to finalize the contract details. The architect recently called me and said he would prefer to build the entire basement with masonry (thickness unknown but thicker than 24cm (10 inches)), including drainage. The drainage would not clog because it would be in a gravel bed.
I have researched and, as expected, I am uncertain about which option is better and what questions I should ask the architect or what details should be agreed upon.
Basically, there are two methods: waterproof concrete (often called a white tank) and sealing with bitumen or plastic membranes (often called a black tank).
Regarding the cost of both options, I have read very different statements; for some, one was more expensive, for others, the other was. Or it was previously like that, but now they say the costs are about the same. The waterproof concrete method is said to be much more common nowadays.
I also found, but only from one source (other sites had exactly the same text), that bitumen variants last only about 30 years, while waterproof concrete easily lasts 80 years. Is there any truth to this? Has anyone had to remove their soil because water appeared after 30 years?
Back to the upcoming discussion with the architect. Should he provide a written guarantee of watertightness? Is the concrete method definitely waterproof and generally requires less long-term warranty? What else should I pay attention to (I won’t sign immediately, but a more confident approach wouldn’t hurt)? What might be a rough but reasonable wording for both options in the contract?
Thank you very much.
In the case of a sloped site, I think not connecting to the rainwater drainage system is not a big issue, since the water is still directed sideways past the house, preventing direct impact on the building.
I have now discussed this topic with an architect (the one designing the house) and an engineer (from my acquaintances).
Our architect left it up to me to choose between masonry or concrete.
Here are the two options I can select from (regarding a wall in contact with the ground / facing the slope):
Masonry
- 42cm (17 inches) hollow brick masonry
- Sealing material RSB 55Z
- Dimpled membrane (drainage board)
- No gravel layer
- Drainage at the level of the floor slab for lateral water drainage, possibly with inspection chambers
Concrete
- Watertight concrete (thickness unknown)
- Thermal insulation layer (thickness unknown)
- No sealing material (unnecessary due to watertight concrete)
- No drainage (unnecessary due to watertight concrete)
The architect mentioned as an advantage of masonry that, for thermal insulation reasons combined with creating a support surface for the facing bricks, it is simpler.
Another advantage of a masonry wall is that there is no transition joint to the rest of the basement wall above ground, which will definitely be masonry, so the entire structure would be monolithic.
He also stated that a masonry basement leads to a better indoor climate.
I have often read and heard this last point, both dismissed as a "myth" and then again acknowledged as "probably true." Some colleagues reported that they have actually noticed a better indoor climate in masonry basements compared to neighbors' basements built differently. I am not in a position to judge, but I tend to believe in the "better indoor climate" to some extent.
The engineer I know confirmed both approaches presented by the architect.
He built his own house himself using masonry because he was able to do it on his own and had no options for concrete.
Due to groundwater, their house is constantly surrounded by water; they had to use a sump pump at the time, and when it failed overnight once, the excavation pit was a complete pond the next morning.
He has had no moisture problems in the basement for about 30 years now.
He says that if we build with drainage, it would not be a problem to avoid using watertight concrete, although the latter would certainly be more reliably waterproof.
From the perspective of our close electrician acquaintance (doing electrical work himself), a masonry basement would be advantageous for interior installations.
Overall (based on my interpretation), a masonry basement has almost only advantages except for the issue of waterproofing.
The latter remains a big unknown that no one wants to predict.
The statements from the people mentioned above contradict most of the comments in this thread.
As it stands, I would flip a coin but tend to trust those I have met personally.
Otherwise, I am considering a consultation with a supposedly independent expert.
I have now discussed this topic with an architect (the one designing the house) and an engineer (from my acquaintances).
Our architect left it up to me to choose between masonry or concrete.
Here are the two options I can select from (regarding a wall in contact with the ground / facing the slope):
Masonry
- 42cm (17 inches) hollow brick masonry
- Sealing material RSB 55Z
- Dimpled membrane (drainage board)
- No gravel layer
- Drainage at the level of the floor slab for lateral water drainage, possibly with inspection chambers
Concrete
- Watertight concrete (thickness unknown)
- Thermal insulation layer (thickness unknown)
- No sealing material (unnecessary due to watertight concrete)
- No drainage (unnecessary due to watertight concrete)
The architect mentioned as an advantage of masonry that, for thermal insulation reasons combined with creating a support surface for the facing bricks, it is simpler.
Another advantage of a masonry wall is that there is no transition joint to the rest of the basement wall above ground, which will definitely be masonry, so the entire structure would be monolithic.
He also stated that a masonry basement leads to a better indoor climate.
I have often read and heard this last point, both dismissed as a "myth" and then again acknowledged as "probably true." Some colleagues reported that they have actually noticed a better indoor climate in masonry basements compared to neighbors' basements built differently. I am not in a position to judge, but I tend to believe in the "better indoor climate" to some extent.
The engineer I know confirmed both approaches presented by the architect.
He built his own house himself using masonry because he was able to do it on his own and had no options for concrete.
Due to groundwater, their house is constantly surrounded by water; they had to use a sump pump at the time, and when it failed overnight once, the excavation pit was a complete pond the next morning.
He has had no moisture problems in the basement for about 30 years now.
He says that if we build with drainage, it would not be a problem to avoid using watertight concrete, although the latter would certainly be more reliably waterproof.
From the perspective of our close electrician acquaintance (doing electrical work himself), a masonry basement would be advantageous for interior installations.
Overall (based on my interpretation), a masonry basement has almost only advantages except for the issue of waterproofing.
The latter remains a big unknown that no one wants to predict.
The statements from the people mentioned above contradict most of the comments in this thread.
As it stands, I would flip a coin but tend to trust those I have met personally.
Otherwise, I am considering a consultation with a supposedly independent expert.
After yesterday’s discussion with employees from the building materials supplier and a friend who is a young architect, I have decided to go with a waterproof concrete basement. It was strongly recommended to me from all sides. One of the supplier’s staff has already supplied other houses in the same development (similar slope) and, as he says, is familiar with the hill from another area as well, and particularly recommended the waterproof concrete basement.
The mentioned friend/young architect also suggested considering a "fresh concrete bonding membrane," which is supposed to ensure the vapor-tightness of the waterproof concrete. Otherwise, with moderate water pressure, a cardboard box placed directly next to the concrete wall could become damp and wavy.
I find information about this mainly from manufacturers themselves, describing that the membrane is embedded inside the concrete from the interior.
Has anyone had experience with this?
The mentioned friend/young architect also suggested considering a "fresh concrete bonding membrane," which is supposed to ensure the vapor-tightness of the waterproof concrete. Otherwise, with moderate water pressure, a cardboard box placed directly next to the concrete wall could become damp and wavy.
I find information about this mainly from manufacturers themselves, describing that the membrane is embedded inside the concrete from the interior.
Has anyone had experience with this?
An architect who also acts as the contractor can be a cost-effective solution, in my opinion, when building properties for their own rental portfolio. However, this arrangement is less favorable for the typical client-homeowner: from the client’s perspective, the architect should advocate exclusively for the homeowner’s interests, while the contractor has their own priorities (such as completing the project cheaply “at purchasing costs”) and is content as long as the building lasts through the warranty period (which, according to the German Construction Contract Procedures – VOB, is shorter than the statutory building code warranty). This influences the choice of building materials and construction methods: concrete work requires a high proportion of skilled, experienced workers, whereas bricklaying can involve apprentices, and labor costs more than materials. Just my 2 cents ;-)
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
Kaspatoo schrieb:
I have now received the following proposal from the architect, and I think it looks quite solid.My initial spontaneous look at the drawing suggests: half a centimeter (0.2 inches) more "air gap," and you stay neat inside and outside within the modular grid.https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
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