Basement made of high perforated bricks or concrete?

Hello everyone,

we are currently in the planning phase for our basement. After evaluating some house offers, two options are available for the construction of the basement:

1.) Construction of the basement with 36.5 cm hollow bricks

2.) Precast concrete basement or basement made of 24.5 cm concrete

Both are to be built on a suitable base plate. The plot is completely level and we have been informed by the municipality that, due to the soil conditions and groundwater level, it is not necessary to plan a basement made of waterproof concrete or [Weiße Wanne]. The basement should have a height of 2.80 m (shell construction dimension) because it will be used as a granny flat afterwards. For the most part, "normal" windows will be installed. The basement will have a separate entrance. The necessary installations (electricity, water, heating) will be planned as concealed installations.

After some discussions with the builders, we have not made a concrete decision yet. However, there are many pros and cons for both options!

Some say that the basement made of hollow bricks is better in terms of climate than the concrete basement. Others say that you probably do not notice the difference compared to the concrete walls. The concrete basement is more resistant and watertight in case of possible moisture intrusion but must be separately insulated with 120 mm rigid foam boards for thermal insulation. For the basement made of hollow bricks, a plastic-modified bitumen thick coating (at least 3 mm) would address the same issue! A separate insulation is no longer necessary due to the wall thickness.

Now the question for us is, which basement is better? Who can help us with this?

Thank you very much in advance.

Hello home builder,
now you have been active in the forum for so long and then this:

The plot is absolutely flat and the municipality has informed us that it is not necessary to plan a basement made of waterproof concrete or a white tank due to the soil composition or groundwater level.

Of course you have that in writing from the municipality and any potential costs for pumps and the tank will be covered by the municipality? So: first have a soil survey conducted.
Why a basement if the plot is flat, have you included the disposal costs for the excess soil, 10k can quickly be gone there.
Regarding the question itself, concrete is less sensitive to moisture and quick and precise to build. Chiseling slots for electrical installations is off the table, so plan everything in advance and have it prefabricated at the factory. Walls are smooth formwork and can be wallpapered directly.
How deep do you want to go into the ground, how does light get into the granny flat, I wouldn’t want to move in there without floor-to-ceiling windows.
Cost-wise this will be a real challenge, just for an outside staircase with a front door you can quickly spend 5k, overall you can expect about 50% of the pure house costs for the basement. So don’t be surprised if the fun later costs 70-80k.

Details Basement

Hello 6Richtige,

thanks again for your hint. We have learned from the InovaHaus case. The municipality has commissioned a soil survey for the new development area, thus also for our building plot. Apparently, this is common practice in the region. Based on this, we were informed that a waterproof basement is not necessary.

Of course, I am not a geologist either and I don't know what will happen in the next 40 years. But the soil survey only represents a snapshot in time. The houses in this new development area are partly built from masonry (Poroton) and prefabricated concrete parts. Both neighbors are very satisfied with their respective basements.

Back to the windows, even though it was not asked, they are completely normal living space windows and not basement windows! There is only one typical basement window, since it is located under the terrace.

By a level plot, I do not mean a sloping site! The costs for excavation and earthworks have already been defined. The depth of the basement is about 180 cm. Thus, the daylight (southwest side) is well ensured. Besides, only my son goes down there!

The outdoor stairs and the separate entrance were already calculated cost-wise beforehand. Of course, this will not be a "normal" basement.

The question for us now is, which is better: the masonry or the prefabricated concrete basement?

Your argumentation regarding the wall surfaces is indeed correct. But if we come up with something else in a few years, like laying new pipes etc., there might be difficulties! With the masonry basement, additional chases can be made quickly.

Hmmmh, 1m above ground level? No problems expected with the eaves/ridge height? You might be able to spread the excavation on the property, which could result in a steeper path to the house or garage, depending on how close the house is. If you want to chisel grooves later, go for the brick cellar with a black tank, better safe than sorry.

Hello, house builders

All our acquaintances who have built cellars from stone have problems with water. There was no groundwater present. In one case it was due to rainwater pipes, in another case because of a neighbor who simply lets rainwater sink into the ground (great!).
We then had to dig up again and fix the problems.

Regarding drilling in concrete. We have a concrete cellar. And we did not want to have the installation surface-mounted. We laid empty pipes in the cellar ceiling, then concrete was poured on top. Now the pipes are in the concrete and the lines can be routed as desired. If you think ahead a bit about what could come, you can also handle the problem well.

Concrete basement

Hello Schornstein,

thank you very much for the information.
Did you award the basement as a separate contract or was it part of the complete contract with your builder?
Which basement manufacturer did you have?