ᐅ Waterproofed Basement – What Additional Costs Can Be Expected?
Created on: 11 Oct 2017 23:28
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Steffen F
Dear experts,
we (4 parties) are currently building a 4-family house. The basement and the walls on the ground floor and first floor were supposed to be completed by now. Unfortunately, groundwater was discovered during the excavation of the building pit. This has, of course, changed a lot.
The basement builder now demands approximately 36,000 Euros in additional costs for a waterproof (WU) basement compared to the originally planned basement. Are these additional costs realistic and normal?
Originally planned:
Reinforced concrete slab 18 cm (7 inches) thick on a foil covering (approx. 150 sqm (1,615 sq ft)),
Gravel filter layer 15 cm (6 inches) thick with area drainage function,
Shotcrete walls C25/30 20 cm (8 inches) thick with bituminous thick coating on the outside and perimeter insulation (approx. 125 sqm (1,345 sq ft)),
Clear height of basement rooms 2.50 m (8 ft 2 in);
Originally planned construction costs for the basement: approx. 100,000 Euros.
Now planned for the waterproof (WU) basement:
Reinforced concrete slab 30 cm (12 inches) thick,
Increased consumption of reinforcing steel,
Gravel backfill 1.70 m (5 ft 7 in) around the basement as a drainage layer,
Concrete quality C30/37,
Increased excavation volume,
Clear height of basement rooms 2.30 m (7 ft 7 in);
Additional costs for this: 26,900 Euros.
In addition, waterproof construction charges for concrete additives, special construction materials, pipe penetration elements, and construction services amount to another 6,500 Euros.
This results in a total of 33,400 Euros in additional costs.
Can you assess whether these additional costs are reasonable or if these prices seem exaggerated based on your experience?
I would be very grateful for your evaluation.
Best regards
Steffen Frey
we (4 parties) are currently building a 4-family house. The basement and the walls on the ground floor and first floor were supposed to be completed by now. Unfortunately, groundwater was discovered during the excavation of the building pit. This has, of course, changed a lot.
The basement builder now demands approximately 36,000 Euros in additional costs for a waterproof (WU) basement compared to the originally planned basement. Are these additional costs realistic and normal?
Originally planned:
Reinforced concrete slab 18 cm (7 inches) thick on a foil covering (approx. 150 sqm (1,615 sq ft)),
Gravel filter layer 15 cm (6 inches) thick with area drainage function,
Shotcrete walls C25/30 20 cm (8 inches) thick with bituminous thick coating on the outside and perimeter insulation (approx. 125 sqm (1,345 sq ft)),
Clear height of basement rooms 2.50 m (8 ft 2 in);
Originally planned construction costs for the basement: approx. 100,000 Euros.
Now planned for the waterproof (WU) basement:
Reinforced concrete slab 30 cm (12 inches) thick,
Increased consumption of reinforcing steel,
Gravel backfill 1.70 m (5 ft 7 in) around the basement as a drainage layer,
Concrete quality C30/37,
Increased excavation volume,
Clear height of basement rooms 2.30 m (7 ft 7 in);
Additional costs for this: 26,900 Euros.
In addition, waterproof construction charges for concrete additives, special construction materials, pipe penetration elements, and construction services amount to another 6,500 Euros.
This results in a total of 33,400 Euros in additional costs.
Can you assess whether these additional costs are reasonable or if these prices seem exaggerated based on your experience?
I would be very grateful for your evaluation.
Best regards
Steffen Frey
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nightdancer12 Oct 2017 14:13If you build without your own expertise, this is exactly what you end up with: botched work. A waterproofing membrane must be contractually agreed upon (which clearly isn’t guaranteed here), well planned, and carefully supervised because it is prone to damage. It would be interesting to know why you need a gravel drainage layer, probably because it sounds good and can be charged separately. The construction will definitely become more complicated overall and significantly more expensive, plus more building defects.
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nightdancer12 Oct 2017 14:16Curly schrieb:
I think the additional cost compared to the basement price of 100,000 euros is quite realistic. A thicker concrete slab, more steel reinforcement, and so on—that all costs more. A friend of ours also had to build a waterproof concrete shell ("white tank") (in 2006), and back then they already faced an extra charge of 30,000 euros.
Best regards,
SabineI have a friend who built a house two years ago and had an extra cost of 3,000 euros. I wonder what that was due to...