Can my walls made of lightweight aerated concrete handle the loads from the roof?

[Husvagnsthord]

Hello

I have a house about 11x7 meters. One and a half stories. Built in 1930 with lightweight concrete of unknown density. We are going to furnish the upper floor. With a new sheet metal roof and reinforced trusses with space for insulation. The house has stood for maybe 90 years. But when I look at the slim outer walls of only 10 cm thick lightweight concrete, I wonder if they really can handle the load from the roof in snow zone 2.5?

The roof slope is about 45 degrees. The roof area will then be about 115 m2. The new roof will have several dormer windows so I think 130 m2 is closer to the new truth.

It's not just me wondering, the Municipality apparently wants to know too.

Anyone here who can give a clue.

 

[klaskarlsson]

Has the old roof been covered with tiles?
If you replace it with sheet metal, which is lighter, and the house has stood for 90 years, I wouldn't be worried.
It's a bit tricky if you don't know the strength of the concrete.
A search here on Bh yielded among others:
"To avoid making it more complicated than necessary, it can be expressed that lightweight concrete in its "warmest" density (350 kg/m3), i.e., the one with the lowest strength, is quite sufficient for 1.5-story houses. If building 2-story houses, one should choose 400 kg/m3 on the ground floor and 350 kg/m3 on the upper floor"
https://www.byggahus.se/forum/stenhus/26433-kvalitet-pa-lattbetong.html?perpage=15#post95997

Otherwise, it might become necessary to reinforce with beams or similar constructions?

BTW, the roof trusses didn't look overly dimensioned either?

/K

 

[Husvagnsthord]

Thanks for the quick input, klaskarlson. Today the sheet metal is basically lying directly on the rafters, which are not exactly over-dimensioned. They are 3x5 inches, i.e., 75x125 and should be considered a standard dimension from that time. They will be accompanied by 300 mm kerto.

The density of the lightweight concrete does play a role. But also the thickness, in my opinion. Blocks for exterior walls are today +300 mm. This means that the load from the roof is only a third per unit area compared to what my blocks need to handle.

The alternative, as you say, is to transfer the loads to the foundation via new beams. I suspect that's where much is pointing. But I would preferably avoid that.

Does anyone else have any opinions?