ᐅ Prestressed concrete slab on timber beam ceiling

Good day, I am new here.

I came across this forum and noticed that there are some professionals around, so maybe you can help me or give me some advice.

I would like to extend or add onto my parents’ house. What I am wondering right now is whether it is possible to simply place a prefabricated concrete slab onto an existing wooden beam ceiling with a plank floor.

The house was built in 1960 and does not have very thick masonry. My parents live on the ground floor, and the upper floor has a knee wall with a sloping roof. In between there is the wooden ceiling with a plank floor. My plan is to remove everything upstairs, if possible place a concrete slab on top, and then build one and a half stories above that. The concrete slab would likely need to span freely over 8.2 meters (27 feet) since there is no load-bearing wall running completely through the house.

Can anyone tell me if this is basically feasible? Or are my details still too unclear or incomplete?

Thanks in advance.

Hello,

Alex90 schrieb:

I would like to extend or add onto my parents’ house. Right now, I am wondering if it is possible to simply place a precast concrete slab on top of an existing wooden beam ceiling with a hollow-core floor.

The house was built in 1960 and doesn’t have particularly thick masonry walls. My parents live on the ground floor, and the upper floor has a knee wall with a sloping roof. Between those floors is the wooden ceiling with the hollow-core floor. My plan is to remove everything upstairs, if possible install a concrete slab, and then build one and a half additional stories on top. The concrete slab would likely have to span freely over 8.2m (27 feet) because there is no load-bearing wall running through the house.

Can anyone tell me if this is fundamentally possible? Or are my details too unclear or imprecise?

No one here can reliably answer that for you!

You should consult a structural engineer with the existing house documents and have them review the original calculations. That way, you will know exactly what is possible and what isn’t – and the best part is that the engineer you find this way will assume liability.

First and foremost, however, you should check with the building department responsible for existing structures whether adding additional floors is even allowed or can be approved.

Regards, Bauexperte

It could be possible that when working on the new tax advisor ceiling—a wooden beam ceiling—you carefully cut out the necessary sections and secure the rafters, since the beam layer also provides bracing, and have a suitable support in place. Possibly constructed from reinforced masonry (KSV) arranged in a bond pattern, about 30cm (12 inches) thick, with the required recesses or openings. First, schedule an on-site meeting with the structural engineer. For example, I installed a beam below a roof terrace exit according to the structural engineer’s specifications. The living room is about 50sqm (540 sqft) without any supports, plus three double doors, a panoramic window approximately 5.00 x 2.00m (16.4 x 6.6 ft), and a passage measuring 2.50 x 2.50m (8.2 x 8.2 ft). The ceiling height is 3.00m (9.8 ft). It was somewhat more complex to construct. Such a thing will never hold on a wooden beam ceiling (2.8t/m³ (175 lb/ft³)). Of course, everything is coordinated with the local authorities. Great project, it will definitely work!

I didn’t really expect to get a reliable answer. I just wanted to find out if anyone has already done this or if the general consensus is “that’s never going to work” or “yes, I have done/seen that before, and here’s what I had to do.”

I’ll be talking to the authorities soon. For now, I need to find a structural engineer to take a look at the situation.

Overall, it’s going to be quite a big project, especially since there will be a 5.5m (18 feet) extension added to the additional floor. So, this probably won’t be the last time I ask questions.

Thanks in advance for the replies.