ᐅ Masonry Basement or Concrete Basement?

Hello,

we are currently planning a single-family house on a plot with a south-facing slope. The design includes a partially underground basement that is fully below ground level on the north side and completely above ground on the south side.

However, we are quite uncertain whether to choose a masonry basement (brickwork with bitumen thick-layer membrane) or a concrete basement.

A geotechnical survey is not yet available, but for nearby plots, the load case temporarily accumulating seepage water has been identified.

Bricks would be advantageous due to the lower cost, better thermal insulation, and potentially improved indoor climate. Concrete primarily offers more reliable waterproofing. A compromise solution has also been suggested—concrete in the north and brick in the south. I am concerned about possible differential settlement in this case. Are these concerns justified?

The garage is directly adjacent to the house. We might also cellar the garage, which would be used for pellet storage and as a tool shed. Both the garage and its basement should be outside the thermal envelope of the house. What is the general opinion on this? Is it practically possible to avoid thermal bridges in such a configuration?

I would appreciate any suggestions you could offer.

The house we currently live in was built in 1979. It is built on a slope, with the basement underground on the north side and at ground level on the south side. The soil is clayey. Well drained. Constructed with calcium silicate bricks. Interior walls are plastered, exterior walls covered with a type of asphalt coating. Dry and watertight. So far.

Anderl schrieb:
We were also offered a compromise solution – concrete on the north side, brick on the south side. However, I have concerns about differing settlement behavior. Are these concerns justified?

Since concrete would then presumably be used for all (also partially) buried walls, that would mean east and west would also be concrete, and only the south side brick. I find that questionable given the potential overall difference. For reasons related to wall connections, I would also favor calcium silicate blocks over brick. I share the concerns regarding settlement.

Anderl schrieb:
The garage is directly attached to the house. We might also cellar the garage. The garage basement would then serve as pellet storage and a tool shed.

Would the garage basement be separate from the house, accessible only from the outside? – What kind of garage are we talking about: a double garage? – With a single garage, the ratio of wall and excavation effort to usable space is less favorable, which raises questions about the cost-effectiveness of adding a basement.

Anderl schrieb:
The garage and its basement should be outside the thermal envelope of the house. What is the general view on this? Is it possible to avoid thermal bridges at all?

A consistent separation also means no "shared" wall between house and garage. Garages are usually closed off, so they are wind-protected and only ventilated briefly when entering or exiting, which limits heat loss. I believe the idea that garages are full of thermal thieves is a myth. I’d say the garage essentially acts like an air layer with parking spaces.

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Yes, it is a double garage with approximately 40m² (430 sq ft). We have not planned for access from the house basement to the garage basement.

The interior basement walls could be built with bricks, and for the shared wall, bricks filled with perlite could be used. There would still be the thermal bridge over the shared exterior wall and the floor slab.

Anderl schrieb:
The interior basement walls could be built from bricks,

Walls made of sand-lime blocks can be butted directly together, whereas brick walls usually cannot. Furthermore, masonry is more labor-intensive than casting concrete – are you sure this has been accounted for in the cost estimate?

Anderl schrieb:
and for the shared wall, use perlite-filled bricks.

Solid bricks have not been common for some time, and hollow-core bricks are now standard. There are various expert opinions on whether leaving the (air) chambers hollow, filling them, or foam-injecting them is the best approach. Currently, concerns about minimizing heating energy use are somewhat overhyped. It’s possible to take things too far.

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Anderl schrieb:

However, we are very uncertain whether to choose a masonry basement (brick + bituminous thick-coat membrane) or a concrete basement.

Ask an architect and they will tell you that only the masonry option can reliably be made watertight as a basement. Ask a general contractor and they will claim exactly the opposite.

Since part of your basement is planned to be used as living space, I would always recommend masonry.

Anderl schrieb:

Garage and garage basement should be located outside the building’s thermal envelope. What is the general opinion on this? Is it actually possible to avoid thermal bridges?

As long as no walls are "shared," this is not a problem. Your designer must ensure sufficient ventilation is provided.