ᐅ Enlarge and completely renovate a single-family home, or demolish and rebuild?

Tassimat schrieb:

But what do you think about the walls of the ground floor, which are all going to be removed?

I don’t see any indications in the plans of bricks with higher compressive strength or calcium silicate bricks, nor any differences between the interior walls. Apart from the basement, only 11.5cm (4.5 inches) walls are shown. Due to the shallow depth of the house, it’s conceivable that there is no load-bearing central wall.

Tassimat schrieb:

I would be concerned that these walls carry the ceiling elements (which probably explains your question about the ceiling panels), or that the walls have bracing functions, even if they are not load-bearing.

The ceiling plan would clarify what type of ceilings we are dealing with here. A 24cm (9.5 inches) wall only in the basement and not above could indicate different types of ceilings. A few years earlier, it was common to have a reinforced concrete ceiling in the basement, a wooden beam ceiling between the ground floor and the upper floor, and between the upper floor and the attic, a wooden beam ceiling that was structurally part of the roof truss—apparently, this is not the case here. Two assumptions come to mind, which the ceiling plan would clarify: either these are also massive reinforced concrete ceilings, typically spanning two rooms on average, which would usually rest on load-bearing walls at the edges. No such walls can be identified in the floor plan based on wall thickness, so this would have to be solved with bricks of higher compressive strength; such walls are obviously essential and cannot easily be substituted. Or, for example, a hollow-core slab system was used, with continuous beams running parallel to the gable and supplementary reinforced concrete topping. Non-load-bearing bracing walls would not be indispensable but replaceable. Relying on trust alone would neither carry the loads nor resist wind forces, so clarification is needed.

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11ant schrieb:

I didn’t mean the construction file in the sense of Grandpa’s folder on the house build, but the box in the town hall archive with the original building permit documents from back then. We can also discuss this without those, but then it becomes quite speculative, and the structural engineer doesn’t work with a crystal ball either...

There are no building plans for our house either, let alone the ceiling plans. I even visited the city’s building archives, and there was only the building permit. Unfortunately, not every house has these documents. Ours is only 100 years old, so you would expect such records to still exist.
We simply opened up a spot in our house and checked how the ceilings are constructed, which beams are placed at what intervals. We carefully noted everything.

Winniefred schrieb:

There are no construction plans available for our house, not even ceiling plans. I even visited the city’s building records archive, but they only had the building permit. Unfortunately, such documentation doesn’t exist for every house. Ours is only 100 years old, so you would expect something like that to still be available.

No, on the one hand, it is actually quite normal that there are no ceiling plans (and never were). On the other hand, any existing documents would only be there by chance, since a house built around 1920 has already survived World War II. More archives were destroyed by bombings than Napoleon supposedly said could be shredded from the Caesar era ;-)

In the Middle Ages, there was still a lot of chaos, and urban settlement patterns were still new. The main driver of building regulations at that time were devastating fires. The first zoning plans aimed to control irregular street edges by setting building alignment lines — so early development plans were very simple: there was a building line along the street, and a ridge height restriction of “not higher than the church tower.” Even during the Imperial era, there were few rules; for example, in Berlin, there was a regulation on eaves height based on the idea that the facade of a house could collapse like a falling tree without hitting the opposite row of houses, and in inner courtyards, the turning radius of the fire ladder truck was the key measure. Structural calculations required for building permits are a relatively recent innovation, and wooden beam ceilings did not contain any steel reinforcements at all.

Winniefred schrieb:

We simply opened up one section to inspect how the ceiling was constructed and to note the spacing of the beams. Everything has been carefully documented.

Wood beam ceilings are very helpful for building forensics, but in this case, that only applies to the ceiling between the attic and the roof space, while the ceiling that needs clarification is actually the one between the ground floor and the attic.

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We currently have a very similar project and have just decided to demolish and completely rebuild. Since the house already has a basement, the excavation for a new basement is at least already done. The house is a basement bungalow with just under 80 m² (860 sq ft) on the ground floor, situated on almost a four-digit square meter plot in a very good location. However, it has no real value or features that make it worth preserving. The structure is unfortunately still quite solid, so the demolition will be a little difficult.

The reasons after two meetings with architects were ultimately:

- Adding a floor was ruled out because the ground floor would have to be raised due to the underfloor heating, making all the windows and doors too low. This would require so much work on the masonry that it would be better to simply rebuild the ground floor.
- Demolishing the ground floor down to the basement was also ruled out because it would mean too many compromises (pipes, access, floor plan itself), especially since an extension is attached to the ground floor.
- There is significant uncertainty in the cost estimate for almost every trade due to the “we’ll have to see what we’re dealing with” factor.

The structural framework would have allowed it, but the combination of too many compromises and uncertainties was the deciding factor in the end.

Araknis schrieb:

We currently have a very similar project and have just decided on demolition and a complete rebuild.

I hope that’s not the case here and find it very likely to be more than unnecessary.

Araknis schrieb:

Since the house currently has a basement, the excavation for a new basement is at least already there. [...] Demolishing the ground floor down to the basement is not an option because it would require too many compromises (utilities, access points, the floor plan itself).

So you are now doing a full demolition down to the foundation level and only using the excavation pit, even though the upper floor slab (OKKD / upper edge of the floor slab) would have worked height-wise as well?

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This is how you get a nice, warm, insulated basement with sufficient ceiling height 🙂