ᐅ Expansion joint between two terraced houses – responsibility according to DIN standard?

Hello everyone,

We have a single terraced middle house, which has recently had an extension added. The exterior wall facing the neighbor is made of calcium silicate brick, probably 17.5 cm (7 inches) thick, and is unplastered.

The neighbor has attached a prefabricated timber frame extension. Now there is an approximately 5 cm (2 inches) wide gap between our houses. According to my builder, the party adding the extension is responsible for sealing this gap.

From what I understand, this should be sealed by inserting mineral wool strips and/or compressible sealing tape along with a mounting rail. Additionally, a metalworker should install a flashing extension at the roof junction to prevent water ingress between the houses.

My neighbor seems unaware of this and claims their building is designed as a "detached house," even though their timber stud wall facing my property also has open joints where moisture could enter.

Is there any specific standard (e.g., a DIN norm) or regulation that clearly states the responsibility lies with the party building the extension?

I am concerned about the upcoming winter if the neighbor does not take action. Also, I wonder whether compressible tape and the mounting rail alone are sufficient, considering the potential for thermal bridging... I am willing to insert the mineral wool strips myself if necessary, but I am not prepared to cover the costs for the rest.

Why should the person building the extension be solely responsible for this? That doesn’t make sense to me and sounds illogical.

I assume it means sharing the costs here.

Chris1110 schrieb:

We have a single terraced middle house, to which an extension has been added now, [...] The neighbor has added a prefabricated timber frame extension. Now there is a gap about 5 cm (2 inches) wide between our houses, and according to my developer, the builder of the extension is responsible for closing it. [...] My neighbor claims ignorance on this matter and points out that he has a designed "detached house," although his timber frame wall adjoining mine also has open gaps where moisture could penetrate.

If there really was one developer responsible for the entire terrace row, this problem wouldn’t exist. So you were bold enough as an individual builder to construct what was initially a free-standing terraced middle house, to which neighboring houses were then added unsystematically (?) – ouch. I have a little horror story for you: the case of @goalkeeper: https://www.hausbau-forum.de/threads/reihenendhaus-mit-gue-in-eigenregie-bauen.31198/

tomtom79 schrieb:

Why should the builder of the extension be solely responsible for this? That doesn’t make sense to me and sounds illogical.
Probably the costs should be shared here.

I also consider a shared cost contribution appropriate here. However, I must disagree with your assessment of this as "illogical": conversely, if I were to demolish a terraced house, I alone would be responsible for ensuring not to damage or endanger the neighboring houses. If the neighbor leaves the gap solely to chance, any materials installed there will become saturated unprotected and damage the wall of the house of the original poster. I think a polite legal request would be appropriate, asking the neighbor to instruct his house manufacturer to provide information on how this whole situation should be handled. Given the different materials and construction times, this separation joint has an important role as a construction joint, which I would definitely keep exposed, ventilate, and only seal carefully around the edges. This joint is not a cosmetic detail that can be omitted, but a very important element that must be carefully planned and executed. I clearly see the last builder as responsible here. Also—for this reason—I would not waive legal advice. The entire matter should be agreed upon mutually. I wish you good luck with Mr. Komischervogel as a neighbor, hopefully without Serbian friends rushing to @HilfeHilfe first ;-)

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11ant schrieb:

I also consider a shared cost contribution to be appropriate here. However, I disagree with your assessment that it is "illogical": if, on the other hand, I demolish a terraced house

So, do both parties have to pay, or just the one who is adding on? You seem to contradict yourself.

I say both have to pay.

When it comes to demolition, what can you reasonably ask for in terms of protecting the facade? Using protective sheeting or even plastering it? I would say it depends.

Chris1110 schrieb:

According to my information, this should be sealed by inserting strips of mineral wool and/or compressible sealing tape along with a rail. Additionally, a metalworker should add an overhang at the roof connection to prevent water from entering between the houses.

How much does it cost? What amounts are we talking about?

Chris1110 schrieb:

My neighbor appears unaware of this and refers to having a designed “detached house.”

Unaware in terms of technical know-how on how to properly resolve this? Does he really not care about the risk of water intrusion? Or is he just trying to avoid paying anything?

Chris1110 schrieb:

My neighbor seems unaware of the issue and insists he has a designed "single-family house," even though his timber frame wall bordering mine has open joints where moisture could penetrate.

I would try reasoning with him one more time:

• No single-family house is built to have another wall only 5cm (2 inches) away.
• If the gap remains open, our houses will suffer damage.
• Due to the building materials, probably yours will be affected faster than mine, but mine will only withstand the first winter. (Unsubstantiated claim, but whatever)

This shouldn’t be terribly expensive. Maybe your neighbor is currently short on money. One solution could be to have the work done and assist with bridge financing (if that’s feasible for you). Ultimately, I hope you’re not foolish enough to leave the gap open and put your house at risk just because of a little money. It will be done anyway if stubbornness, principle riding, or any other irrational factor blinds reason.