Steel support for roof construction - theory meets practice

Hello everyone,

our construction has now progressed to the point where the carpenter could basically erect the roof truss. Now theory meets practice. According to the execution plan and the structural engineer’s documents, 3 steel supports are planned for the roof construction, which are located in the masonry (11 cm wall, 80 mm steel support).
The execution plan states that the recess for the steel support should be filled with concrete afterwards. The builder would carry out the whole thing according to the plan, the carpenter advises against it, as later cracks could appear in the plaster between the masonry and the filled recess. Structural engineer/architect and builder agree on this.

I would like to gather some experience from you and ask whether the purlins of the roof, which are supposed to rest on the steel supports, actually move so much later that the plaster could form cracks.

Thank you in advance for your answers.

Hello, I have attached a picture showing how I imagine your concern. I suspect it was similar for us; steel supports are incorporated into the walls in a few places and filled with "concrete" (here in the picture, the dark vertical "line" at the "back" in the otherwise light wall). So far (lived in for over 2 years) there are no cracks visible at that spot, although there is a relatively thick fleece wallpaper and paint over the plaster, but I just felt it and apparently there is no crack underneath. The indoor temperature hardly fluctuates over the year.

Hello Saruss,

thank you very much for your response. That is exactly how it will look with us later, or rather, that is the plan. Both parties certainly have their reasons for recommending or advising against it. Therefore, experience reports are important to me.

Actually, I could not care less, because if I notice cracks after a year, I will be standing at our site manager's (architect's) door. However, if better alternatives could be chosen in advance here, then I would choose them.

Thanks again!

Actually, it could be all the same to me, because if I notice cracks after a year, I will stand at the door of our site manager (architect). However, if better alternatives could be chosen in advance here, then I would choose them.

Not quite. Because if you deviate from the specified execution planning of your architect, he will rightly show you the door ... if you follow the carpenter’s suggestion and problems subsequently arise

Send the carpenter to the architect; let them discuss it professionally!

Rhenish regards

I wonder what the carpenter's alternative solution looks like? 80mm post in 110mm masonry, there isn’t much material left. I have 6 posts in my purlin roof. I built the posts into the walls, but so that there is a small gap between the masonry and the post. However, I have 17.5mm sand-lime bricks. The gap is to prevent as much sound transmission as possible. At the points where the posts are built in, mesh will be used later during plastering. This should definitely be done for you as well.