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Flat roof structural questions


Tetrarch

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Probably need an SE to get the definitive answer.

 

On a 3.5 x 8.5m span warm roof with multiple skylights, how much extra height would I have to sacrifice to accomodate a sedum roof? The rubber4roofs website states a value of 120kg per sq m which sounds like a lot and would equate to additional load of ~3.5 tonnes, which I am assuming would need much larger structural supporting beams

 

Regards

 

Tet

 

 

 

 

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I was just looking at the density of topsoil yesterday - a glamorous life eh? It's about 1.4T / m^3. Google says a sedum roof should have 70-200mm of topsoil - so 1.4 * 7% = 100 Kg / m^2 and 1.4 * 20% = 280 Kg / m^2.

 

So, yeah - 100-280 Kg per m^2. Putting it another way, 120 Kg per m^2 is about 85mm of topsoil.

 

My present roof (pitched tile) presents a load of ~1.6 Kn/m^2 i.e. ~160Kg/m^2. I appreciate yours is flat and probably more lightweight construction - tiles are heavy (I see they're about 1/3rd of the loading).

 

So yeah, an extra 120Kg/m^2 sounds like it would make a sizeable difference.

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