Croatia - Structural engineer requires 23cm casting against existing interior wall

[mvs]

Making a counter cast on a wall requires extensive knowledge in forming, as the pressure on the form becomes double. Strutting and anchoring are very important to get right.
I think it would have been better to build up the walls with an air gap between the old wall and the new inner wall.

I have actually seen that they did exactly what you are suggesting in some of the houses there - i.e., air gap and then built with bricks. However, as cpalm mentioned, it feels a bit sad to build a "house within the house." Increasingly considering whether maybe timber joists are the right way to go. Losing ten percent of floor space doesn't feel great. And the window frames will become almost 1m deep.

 

[myrstack]

Given the situation and what you describe as a denser older city center, can a concrete mixer and pump truck get in?

Building up a construction, possibly columns, seems like a significantly simpler exercise with the logistics. Then considering a cast floor slab only increases the dimensions of other parts due to its own weight, and if there's an earthquake aspect, isn't the elasticity of a wooden floor slab preferable?

 

[mvs]

Some of you have reached out and asked where this is. I won't be stingy, so here's a 2-minute long video that gives a good overview of the house's location:

0:49 into the video, you can glimpse a light yellow house in the upper part of the picture. That is the house we will be renovating.

 

[Plupp 405730]

Some of you have reached out and asked where this is. I won't be stingy, so here's a 2-minute long video that gives a good overview of the house's location: [media]
0:49 into the video, you can glimpse a light yellow house in the upper part of the image. That is the house we will be renovating.

Magically cozy🤩

 

[cpalm]

The problem is that most of the wooden joists in the really old houses there are undersized.

Yes, that might be the case. Or something may have happened over time that affected the load-bearing capacity.

But that's nothing you need to worry about if you are building a new joist from scratch. The support in the wall for the floor joists would likely need to be moved/changed/added anyway if you have different spans and levels.
There might be a point to a concrete layer in, for instance, a bathroom, but otherwise, I'm a bit hard-pressed to see any advantages with it.

 

[mvs]

Given the situation and what you describe as a denser older city center, can a concrete truck and pump truck get in?

Building a structure, possibly pillars, feels like a much simpler logistical exercise. Considering a concrete slab would only increase the dimensions of other components due to its own weight, and if there is an earthquake aspect, isn't the elasticity of a wooden slab preferable?

We had a company on site last year that looked into it. They claim they can position a concrete truck in the square and then place an auxiliary pump in the garden. From the truck to the house, it's about 40m.

Regarding earthquakes and elasticity, you might be right. Not major quakes in the area like in other places around the Mediterranean, but some smaller ones can occur.

 

[mvs]

The supports in the wall for the floor joists probably need to be moved/changed/added if you have different spans and levels.

Yes, that would be optimal if possible.

At least one wall is built with large boulders, so I'm unsure if we can freely choose how to set the joists. If we move one such large stone, the whole wall might collapse.

Perhaps we can keep 20cm stubs of the existing joists and then place the new joists on top of these. That way we get the ceiling height, don't need to dig into the walls, and we can place something under the new joists where needed to get everything level?

 

[nino]

Should be possible to drill new holes?

 

[Farstatjej90]

The problem is that most of the wooden frameworks in the really old houses there are incorrectly dimensioned. And the beams are usually mounted at slightly different heights, so the floors often slope significantly. Many then try to stabilize and even out by laying a thin layer of cement/concrete on top. It's often seen. Then I wonder if it might not be an advantage with a thin layer of concrete/cement if, like us, you are going to build a bathroom upstairs. If we can freely choose the placement of the supporting beams, I’d prefer to skip a thin layer of concrete/cement, but if we have to use already existing holes for the beams, then I think it might be worth applying a thin layer of concrete/cement on top.

Sorry, I have to comment on this, a house that has stood for 300 years - with an "incorrectly dimensioned framework" - one wonders how many of the houses being built today will still stand in 300 years.

I get what you mean but... Perspective!

 

[cpalm]

If we move such a large stone, the whole wall is likely to collapse.

I don't think so; it's probably much more stable than one might think. Just need to find someone who knows what they're doing.

 

[mvs]

Should be possible to drill new holes?

Maybe, but it probably depends on what type of rock the stone is made of.

 

[Plupp 405730]

If the house has stood for 300 years with masonry natural stones, it is not the quality of the stones that has kept the wall standing but rather the weakness of the lime mortar or whatever mixture they used that has allowed movement, such as for example, during an earthquake, allowing the wall to stand even today. If you build according to Swedish standards, the wall wouldn't survive 100 years, if even that...this is because we use far too strong mortars in today's society...

 

[paralun]

If the house has stood for 300 years with masonry natural stones, it is not the quality of the stone that has kept the wall standing, but it is the weakness of the lime mortar that has allowed movement, such as an earthquake, which makes the wall still stand today.
If you build according to Swedish standards, the wall would not survive 100 years, if even that.

Yes, but now Croatia is located in an earthquake-prone zone.
You have to carefully check how Croatians themselves view this and the regulations. It's not something a foreigner can change.

Briefly on this:
https://www.swedenabroad.se/sv/om-u...nformation/naturförhållanden-och-katastrofer/

 

[Plupp 405730]

Yes, but Croatia is located in an earthquake-active zone.
You have to carefully check how the Croatians themselves view this and the regulations. It’s not something a foreigner can change.

Briefly on this:
[link]

Now, you probably can't instill anything about masonry so that it turns out well, but you know that😉

 

[Farstatjej90]

Sure, but Croatia is located in an earthquake-active zone.
One must closely check how the Croatians themselves view this and the regulations. It's not something a foreigner can change.

Briefly about this:
[link]

Ask someone else?
Hey, we Swedes here at Byggahus know this, ok? Earthquake? We've got it all under control. If the Croatians need a consultant, just start a thread here on Byggahus or send a PM.