Hello everyone,
We are currently in the early phase of the shell construction of our single-family house with a basement garage. The garage basement has already been built, and the slab for the single-family house will follow in one or two weeks.
Our builder warned us yesterday during a conversation that we will definitely see significant cracks in the concrete ceilings, because in his opinion, too much steel reinforcement (a total of 16 tons for the entire structure; footprint of the single-family house 290m² (3,123 sq ft); footprint of the basement garage 130m² (1,399 sq ft); we have many beams and lintels, etc.) was calculated by the structural engineer, and from his experience, "too much steel causes cracks". He said that, for example, with the ground floor slab, we will be able to "see through" the surface reinforcement in the form of cracks—that is, parallel cracks will appear where the rebar is located.
What do you think about this statement? Is it normal or worrying?
This naturally makes us feel uncertain. On Monday, we have a meeting scheduled with our structural engineer about this. However, he refuses to conduct a site inspection at the appropriate time to approve the reinforcement, as he claims not to have time for it. (Maybe he wants to avoid potential liability?)
Do you have any advice on whom we could bring to the site instead to inspect the reinforcement before the concrete is poured? Would a building surveyor / structural consultant be allowed or suitable to perform this task, that is, to review reinforcement installed by a third party?
Thank you very much for your input!
We are currently in the early phase of the shell construction of our single-family house with a basement garage. The garage basement has already been built, and the slab for the single-family house will follow in one or two weeks.
Our builder warned us yesterday during a conversation that we will definitely see significant cracks in the concrete ceilings, because in his opinion, too much steel reinforcement (a total of 16 tons for the entire structure; footprint of the single-family house 290m² (3,123 sq ft); footprint of the basement garage 130m² (1,399 sq ft); we have many beams and lintels, etc.) was calculated by the structural engineer, and from his experience, "too much steel causes cracks". He said that, for example, with the ground floor slab, we will be able to "see through" the surface reinforcement in the form of cracks—that is, parallel cracks will appear where the rebar is located.
What do you think about this statement? Is it normal or worrying?
This naturally makes us feel uncertain. On Monday, we have a meeting scheduled with our structural engineer about this. However, he refuses to conduct a site inspection at the appropriate time to approve the reinforcement, as he claims not to have time for it. (Maybe he wants to avoid potential liability?)
Do you have any advice on whom we could bring to the site instead to inspect the reinforcement before the concrete is poured? Would a building surveyor / structural consultant be allowed or suitable to perform this task, that is, to review reinforcement installed by a third party?
Thank you very much for your input!
N
nordanney15 Mar 2026 14:39Salv25 schrieb:
Do you have any suggestions on whom we could bring to the construction site to inspect the reinforcement before concreting? The person overseeing your project. That could be your architect, your own site manager, or your expert consultant. We don’t know who you have hired.
Where are you building? What has been agreed regarding the (possibly mandatory) inspection? Is a structural engineer for testing involved or not required? What kind of contract do you have with the structural engineer? Who has been appointed as the responsible expert for structural safety?
For a multi-million project, you surely wouldn’t be naive enough to leave all that to the construction company just because they claim to be good and you trust them?
Salv25 schrieb:
Salv25
Cracks in concrete slab due to excessive reinforcement? The headline is incorrectly worded; there is no such thing as "excessive reinforcement." What is probably meant is "more/thicker reinforcement was proposed by the structural engineer, but without increasing the overall thickness of the slab." So, it is not really a case of "too much reinforcement" but rather "insufficient concrete cover." The contractor rightly warns that this inevitably poses a significant risk—namely, the risk of spalling.
Salv25 schrieb:
He said that, for example, for the ground floor slab, we will be able to "see through" the top reinforcement in the form of cracks. So, parallel cracks will appear at the locations where the bars are placed. This statement is nonsense. The risk arises from any inadequate concrete cover, whether at the top or bottom. And this phenomenon has nothing to do with visibility; the slab surface would not remain unfinished.
Salv25 schrieb:
On Monday, we have a meeting with our structural engineer about this. However, he refuses to carry out a site inspection to approve the reinforcement at the appropriate time, saying he does not have time for that. (Maybe he wants to avoid potential liability?) A site inspection by a structural engineer is generally not part of their scope of services for a new build, nor is it significant for establishing liability. Such inspections fall under building supervision (phase 8 of the project) and are recommended to be performed by a construction monitoring expert. But since it would be unwise to knowingly wait for a failure to occur when the risk is still avoidable, you should act proactively: the responsible architect should consider, during design phase 5, the reinforcement suggested by the structural engineer and adjust the overall slab thickness accordingly. Naturally, this will increase the slab’s weight, so involving the structural engineer in dialogue is sensible. You will then either have to adjust the building height and the stairs or accept a reduced clear ceiling height due to the thicker slabs.
By the way, it’s a bit unfair of you to just ask for advice here without also sharing your planning process with the community. Projects on the "category @rick2018" level are unfortunately rare here. So: even without a giant underground tank, pool, full-glass sliding facade, and robotic lawnmower, we still want to hear your villa story!
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
H
hanghaus202315 Mar 2026 17:46If the concrete cover and quality are maintained, in my opinion, this statement is incorrect.
Because the top layer of reinforcement is precisely meant to prevent cracks.
Find a structural engineer for verification.
Salv25 schrieb:
"too much steel causes cracks".
Because the top layer of reinforcement is precisely meant to prevent cracks.
Find a structural engineer for verification.
D
derdietmar15 Mar 2026 18:10Hello,
we also used about 16 tons of steel. For 260 m2 (2,800 sq ft) of living space and 50 m2 (540 sq ft) garage (waterproof concrete shell), so a smaller building. And we have no cracks in the concrete slabs. Therefore, the statement that using a lot of steel leads to cracks is obviously nonsense.
I also assume that concrete cover is meant. We had the same issue – first with the ground slab and then with the flat roof slab. The structural engineers calculate the required reinforcement bars with their tools, but they do not (or not sufficiently) consider that crossing rebar also creates greater thickness. Usually, this is not a problem; the distance between the top and bottom reinforcement is simply reduced. However, in some places, there was so much steel that there was actually very little space left for concrete. The day before pouring the elements, I decided on-site with the construction manager to make the respective elements (ground slab and flat roof) 1–2 cm (0.4–0.8 inches) thicker to ensure sufficient concrete cover. The lower layer was uncritical because precast slabs were used.
Here is a photo of a critical spot:
Flat Roof Reinforcement
The thick rebars (2 cm (0.8 inches)) already had to be placed slightly angled/rotated, yet the planned thickness was not achievable.
In further planning stages, such deviations must of course be taken into account (e.g., stair dimensions and floor height, if internal floor slab).
Best regards
we also used about 16 tons of steel. For 260 m2 (2,800 sq ft) of living space and 50 m2 (540 sq ft) garage (waterproof concrete shell), so a smaller building. And we have no cracks in the concrete slabs. Therefore, the statement that using a lot of steel leads to cracks is obviously nonsense.
I also assume that concrete cover is meant. We had the same issue – first with the ground slab and then with the flat roof slab. The structural engineers calculate the required reinforcement bars with their tools, but they do not (or not sufficiently) consider that crossing rebar also creates greater thickness. Usually, this is not a problem; the distance between the top and bottom reinforcement is simply reduced. However, in some places, there was so much steel that there was actually very little space left for concrete. The day before pouring the elements, I decided on-site with the construction manager to make the respective elements (ground slab and flat roof) 1–2 cm (0.4–0.8 inches) thicker to ensure sufficient concrete cover. The lower layer was uncritical because precast slabs were used.
Here is a photo of a critical spot:
Flat Roof Reinforcement
The thick rebars (2 cm (0.8 inches)) already had to be placed slightly angled/rotated, yet the planned thickness was not achievable.
In further planning stages, such deviations must of course be taken into account (e.g., stair dimensions and floor height, if internal floor slab).
Best regards
hanghaus2023 schrieb:
The top layer of reinforcement is exactly there to prevent cracks. It is the concrete cover on both sides that serves this purpose. The reinforcement should be understood as a team and is overall responsible for tension and compression; in this sense, there is no top or bottom.
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
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