Hello everyone!
As is well known, construction cost calculations during the planning phase are based on the gross volume (BRI) and/or the gross floor area (GFA). This applies to all floors of the house, including any basement level.
Considering a basement with typical example values, the costs are as follows:
- based on BRI: 90m² (970 ft²) x 2.7m (8.9 ft) x 340 EUR/m³ = 82,620 EUR
- based on GFA: 90m² (970 ft²) x 960 EUR/m² = 86,400 EUR
- on average, therefore, about 84,510 EUR.
On the other hand, additional costs for a basement are often estimated at around 40,000...55,000 EUR, depending on the equipment and waterproofing.
The sheer scale of these differences causes confusion.
This raises three questions:
1) How do these values relate to each other?
2) What has been the experience of previous homeowners who know the actual costs retrospectively?
3) A partially open basement level on a sloped site is considered a ground floor. In this case, is the calculation always based on BRI/GFA, or is the distinction more between living and utility spaces?
As is well known, construction cost calculations during the planning phase are based on the gross volume (BRI) and/or the gross floor area (GFA). This applies to all floors of the house, including any basement level.
Considering a basement with typical example values, the costs are as follows:
- based on BRI: 90m² (970 ft²) x 2.7m (8.9 ft) x 340 EUR/m³ = 82,620 EUR
- based on GFA: 90m² (970 ft²) x 960 EUR/m² = 86,400 EUR
- on average, therefore, about 84,510 EUR.
On the other hand, additional costs for a basement are often estimated at around 40,000...55,000 EUR, depending on the equipment and waterproofing.
The sheer scale of these differences causes confusion.
This raises three questions:
1) How do these values relate to each other?
2) What has been the experience of previous homeowners who know the actual costs retrospectively?
3) A partially open basement level on a sloped site is considered a ground floor. In this case, is the calculation always based on BRI/GFA, or is the distinction more between living and utility spaces?
B
Bauexperte27 Feb 2013 16:27Hello Yves,
How do you arrive at the values of €340.00 and €960.00? The first one is set too low, and the second – for the utility basement – is set too high....
First of all – a basement remains a basement and does not suddenly become a ground floor overnight. It can only be a basement converted for residential use. And if that is the case, it is calculated as living space; your figure of €960.00 will not get you far there.
With kind regards from the Rhineland
YvesB schrieb:
Considering a basement with typical example values, the following costs result:
- according to gross volume: 90m² x 2.7m x 340 EUR/m³ = 82,620 EUR
- according to gross floor area: 90m² x 960 EUR/m² = 86,400 EUR
- on average therefore 84,510 EUR.
How do you arrive at the values of €340.00 and €960.00? The first one is set too low, and the second – for the utility basement – is set too high....
YvesB schrieb:
3) A semi-open basement level on a sloped site is considered a ground floor. Does this mean that the calculation must always be based on gross volume/gross floor area, or is the distinction more about residential versus utility rooms?
First of all – a basement remains a basement and does not suddenly become a ground floor overnight. It can only be a basement converted for residential use. And if that is the case, it is calculated as living space; your figure of €960.00 will not get you far there.
With kind regards from the Rhineland
Bauexperte schrieb:
How do you arrive at the values of €340.00 and €960.00? The first one is too low, while the second – for the usable basement – is set too high....
First of all – a basement remains a basement and doesn’t suddenly become a ground floor. At most, it can be a basement converted for residential use. And if that is the case, it will be counted as living space; your €960.00 won’t get you very far.
The value of 340 EUR per cubic meter of gross volume corresponds to the medium standard for a single-family house.
The value of 960 EUR per square meter of gross floor area refers accordingly to the building’s external dimensions multiplied by the number of floors.
This approach is based, as far as I know, on DIN 277, and we received such a calculation from the architect. If living or usable floor area were used as a basis, the latter value would naturally be higher, for example 1500 EUR/m².
Example for our current plan: house 7.88m x 10.88m with basement, upper floor and attic, 38-degree roof slope, and 0.75m (0.75 yard) knee wall height:
Cost GFA: 7.88m x 10.88m x 3 floors x 960 EUR/m² = 246,900 EUR
Cost GAV: 728m³ x 340 EUR/m³ = 247,520 EUR
A correction factor of 0.925 is then applied for our region, resulting in an average rounded cost of around 233,000 EUR.
Here, the issue I mentioned becomes clear: the basement costs 1/3, around 80,000 EUR, while elsewhere around 55,000 EUR is assigned?!
In our project, the usable basement includes a garage (27m² (290 sq ft)) with entrance hallway, laundry room, and garage being heated spaces. The main entrance is on this basement level due to the sloping site.
Here you can see the issue I mentioned: the basement costs one-third, about 80,000 EUR, whereas elsewhere it's estimated at around 55,000 EUR?!Of course, the basement costs more then... it has to cover the too-low costs calculated for the living space...
I find it rather odd to value living space and basement space the same...
For example, our architect calculates 1,300 EUR per square meter (about 120 USD per sq ft) for the living area and 800 EUR per square meter (about 75 USD per sq ft) for the basement... gross values!
B
Bauexperte28 Feb 2013 00:20Hello,
With best regards from the Rhineland
YvesB schrieb:Again – who says so? Your architect?
The figure of 340 EUR per cubic meter of gross volume corresponds to the medium standard for a single-family home.
YvesB schrieb:If the source of the first figure is subjective, how can this amount then be considered valid?
The figure of 960 EUR per square meter of gross floor area therefore refers to the exterior dimensions of the house multiplied by the number of floors.
YvesB schrieb:This DIN standard only explains how to determine the floor areas and volumes of buildings in structural engineering; nothing more, nothing less.
As far as I know, this procedure is based on DIN 277,
YvesB schrieb:I have always found it interesting what architects calculate. I honestly don’t believe this amount will be sufficient for your construction project; especially considering the description of the basement and also given the location in Jena.
We received such a calculation from the architect...
Example for our current plan, house 7.88m x 10.88m with basement, upper floor, and attic, 38-degree roof pitch with a 0.75m (0.8 yard) knee wall:
Costs based on gross floor area: 7.88m x 10.88m x 3 floors x 960 EUR/m² = 246,900 EUR
Costs based on gross volume: 728m³ x 340 EUR/m³ = 247,520 EUR
A correction factor of 0.925 is then applied for our region, resulting on average in about 233,000 EUR.
YvesB schrieb:Your architect is using a mixed calculation; because one value is too low and the other too high, the overall price is relatively correctly determined. You cannot assume that one-third of the total sum is attributed to the basement. For a footprint just under 8m by nearly 11m, I would estimate about 40,000 EUR for the actual functional basement including external insulation/plastering on the hillside (about one-third of the area) plus another 10,000 EUR for the garage lining and heating of three likely small rooms.
Here the issue I mentioned becomes clear: The basement costs one-third or about 80,000 EUR here, but elsewhere about 55,000 EUR are assumed?!
With best regards from the Rhineland
OK, I'll try again
In my posts above, I only referred to the pure construction costs, meaning the cost groups 300 and 400 according to DIN 276. You are right, DIN 277 is, of course, only used to calculate volume and similar measures.
The values of 340 EUR/m3 (340 EUR per cubic meter) and 960 EUR/m2 (960 EUR per square meter) are objective and come from the 2012 construction cost index, which should be familiar to you.
Of course, the 233,000 EUR mentioned above is not enough for the project, as this only covers the pure construction costs. Additional incidental construction costs (about 35,000 EUR) and other costs for land, site preparation, etc. (about 70,000 EUR) still need to be added. Our basement is planned to be built as brick masonry.
Jena is not far away, but we are building in a completely different area around Gera – yes, such significant regional differences do exist.
Therefore, the architect’s approach is quite understandable and, based on the actual construction costs reflected in the BKI, also logical for the planning.
The construction cost index, as the term suggests, only covers the pure construction costs (building structure and technical installations).
There is the approximately 50,000 EUR for the basement again. That was exactly my initial point. The approach based on usable area (about 65m2 (700 square feet) in our case) leads to this result with 800 EUR/m2 (about 75 USD per square foot).
Applied to our example, this means 130m2 (1,400 square feet) living area x 1,300 EUR/m2 (about 120 USD per square foot) = 169,000 EUR and the basement 65m2 x 800 EUR/m2 = 52,000 EUR. This totals 221,000 EUR for the pure construction costs.
In my posts above, I only referred to the pure construction costs, meaning the cost groups 300 and 400 according to DIN 276. You are right, DIN 277 is, of course, only used to calculate volume and similar measures.
If the origin of the upper value is subjective, how can this total amount be valid?
The values of 340 EUR/m3 (340 EUR per cubic meter) and 960 EUR/m2 (960 EUR per square meter) are objective and come from the 2012 construction cost index, which should be familiar to you.
I always found it interesting what architects calculate. I don’t believe this amount will be enough for your building project, especially considering the description of the basement and also not in Jena.
Of course, the 233,000 EUR mentioned above is not enough for the project, as this only covers the pure construction costs. Additional incidental construction costs (about 35,000 EUR) and other costs for land, site preparation, etc. (about 70,000 EUR) still need to be added. Our basement is planned to be built as brick masonry.
Jena is not far away, but we are building in a completely different area around Gera – yes, such significant regional differences do exist.
Therefore, the architect’s approach is quite understandable and, based on the actual construction costs reflected in the BKI, also logical for the planning.
The construction cost index, as the term suggests, only covers the pure construction costs (building structure and technical installations).
Your architect uses a mixed calculation; since one value is too low and the other too high, the price is relatively accurately determined. So, you cannot assume that one-third of the total amount is for the basement. For roughly 8 by roughly 11 meters, I would estimate about 40,000 EUR for the pure usable basement including exterior insulation/plaster in the hillside area (one-third of the area), plus another 10,000 EUR for lining the garage and heating three probably very small rooms.
There is the approximately 50,000 EUR for the basement again. That was exactly my initial point. The approach based on usable area (about 65m2 (700 square feet) in our case) leads to this result with 800 EUR/m2 (about 75 USD per square foot).
Applied to our example, this means 130m2 (1,400 square feet) living area x 1,300 EUR/m2 (about 120 USD per square foot) = 169,000 EUR and the basement 65m2 x 800 EUR/m2 = 52,000 EUR. This totals 221,000 EUR for the pure construction costs.
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