Suddenly, cracks have appeared in the plastered chimney

[justusandersson]

When was the house built and in what way? What is the soil made up of? If it is clay, its load-bearing capacity may be affected by drainage at a lower level. Almost all basement foundations are made on undisturbed ground.

 

[Ronald H]

If the cracks are the result of settlements in the chimney, it doesn't matter which plaster was used. How is the chimney founded?

This was done in 1930 and the only thing I know is that when we renovated all the floors in the basement we dug quite a bit below the old floor. The only things that weren't touched are the exterior walls and the load-bearing inner walls, as well as the chimney. In one place we reached the groundwater level. Then everything was filled up with gravel, two layers of something like foam insulation, and new drains, etc., were laid in this. Over this, the floor was cast with plastic pipes for water-based underfloor heating. On top, we have tiles. New drainage was done on the outside at the same time.

So the chimney still stands on what was established in 1930.

 

[justusandersson]

so we dug out a good bit under the old floor

This is absolutely forbidden! You must never excavate below the level of the footings. Especially if the ground consists of any form of clay soil. There you most likely have the cause.

 

[Ronald H]

When was the house built and in what way? What is the soil made of? If it's clay, its load-bearing capacity can be affected by drainage at a lower level. Almost all basement foundations are made on undisturbed ground.

The house was built in 1930. Masonry basement walls on a footing. Perhaps concrete blocks, but I'm not sure. Above this, a wooden house.

Our street runs between two ridges. Our house is at the same level as the street. On the other side of the house, the mountain rises about 5 meters from the house, and we have an upper plateau on the plot at the same level as the upper floor. On the other side of the street, it looks the same. This means that there is probably rock quite close under the house, but I don't know if there is clay or moraine in between and, if so, how much. There is water pressure from the mountain side down towards the house.

The house has stood for 88 years without any major movements, and since we renovated in 2010 without cracks. And now these suddenly appear, and we have heard cracking sounds that we couldn't trace but were probably these cracks. And we had a small flood that dampened the entire basement but only 1-2 cm deep. And in connection with that, a pump replacement with uncertainty about whether it pumps to the same level. So, partially water supply and then drying out again and then possibly the pump's level. The flood has been an insurance matter, and we wonder if this could be a continued part of it. And besides this, what others have mentioned about moisture or drought due to winter.

 

[Ronald H]

This is absolutely forbidden! You must never excavate below the level of the soles. Especially not if the ground consists of some form of clay soil. There you most likely have the cause.

Then I have expressed myself unclearly. We went below the old floor but not below the soles, stopping a bit above.

 

[justusandersson]

We went under the old floor but not under the shoe insoles

That's fortunate. The diagonal cracks cannot be misunderstood, you have some form of settling. I think there's a strong case that this could be a continuation of the insurance matter. I would probably bring in a knowledgeable geotechnical expert for an independent assessment.

I absolutely think it was right to knock out the old floors and insulate under the new ones.