Demolition of attached single-family house

Hello everyone,

Our house is partially basemented and was built in 1965. My mother's house is from 1985 and was attached to our house at that time. We are considering demolishing our house including the demolition of the basement, in order to subsequently build a new house on the same site.

I would like to get a first opinion here from the forum on whether the demolition of the old house can be done without problems or if damage could occur to my mother's house, or what needs to be taken into account.

Attached is the view so you can get an idea. Thanks in advance for your help!

When your mother built the extension, did she build it directly onto the existing building or have a separate building partition wall created? I assume she supported the old house.

Where is the house located?



Rhineland greetings from the road
Construction expert

Hello construction expert,

The house is located in Lower Saxony.
There is a fire protection wall between the buildings. It should also be noted that the lower part of the extension is used by our house (attachment in green "House 1") and the upper floor (attachment in blue "House 2") is used by my mother. However, this part should remain standing! For better clarity, attached again with marking

The demolition of a house in direct connection with adjacent buildings is never a simple matter and should be approached very carefully. Existing foundations must not be undermined without structural protection/excavation pit support. If applicable, even the dismantling of the basement walls may fall below the minimum distance of 2m plus slope according to the inclination ratio 2.1 (slope base/slope height) to the fire wall foundation and trigger protective measures. Settlement cracks should be avoided.

The fire wall foundation can be eccentrically loaded by the still existing original wall after the demolition of the old building. This can lead to deformations and should be proven structurally.

If old basement rooms/foundation trenches are filled in, this must be done with approved material (no construction debris), which is defined and controlled during installation and compaction to later provide a load-bearing and verifiable subsoil for the structural analysis.

In your position, I would first have the existing components at the demolition site (foundation/fire wall) checked and measured in a building survey by an architect/civil engineer/structural engineer. The fire wall must be possibly anchored. If the planned new building is to be fully basemented, the fire wall foundation must be underpinned in sections and extended down to the new foundation base.

The demolition may also require a building permit according to the respective state building regulations; in NRW from a volume of 300m3 of enclosed space.

So the basement is to be completely removed and the house should not be basemented again later. So the "Grenzwand" between the buildings is twice as wide as the other exterior walls.