[OldHouseRenov]

I want to build a 4'X8' shed with a on the garden roof.
I will have a 4'X8' box 10 or 12 inches deep on the roof full of earth.
I was told that each square foot would weight 100lb when the earth is wet.
I live in Montreal so I must also consider 3 feet of snow/ice in winter that will accumulate on it.

My question is what size 4 foot long beams do I need and how many do I need (spacing over the 8 feet) and what size standing beams (2X4, 4x4 or 6x6) do I need and how many (spacing over 8 feet on each side)

Or if you already have a shed plan with a green roof to show me that can hold the weight, I would be most appreciative ! Thank you !

 

[oh'mike]

We have several engineers here---one will be along soon--

As a structure---that is not a lot of weight --so it can be done safely---without huge cost.

 

[Neosastan]

Roof is easy, what are you planning for the walls?

 

[Daniel Holzman]

It sounds like you need to design for at least 100 psf for the soil load (probably should use 120 psf), 40 psf for the snow load, and 10 psf for material. There is a calculator at this location http://www.awc.org/calculators/span/calc/timbercalcstyle.asp

that can help you out. Unfortunately it does not work up to the full loads you have, but it is close, and you can size to the next larger lumber dimension to be conservative.

 

[OldHouseRenov]

So If I used/understood correctly the tool, the lumber below should hold safely even with a 200lb man walking on the roof to harvest his herb garden ?

• For the roof
• 2X8 5feet across (so 8 of them 12" appart) with 3/4 plywood on top​
• And the walls each side holding the roof up
• double 2X12 8feet across resting on six(6) 4X4 each 16inches apart (8 feet tall on one side to 7.5 feet on the other so to give 0.5' pitch to the roof)​

 

[OldHouseRenov]

Hi and thank you. I am new to this forum and still learning how it works. I replied to my own post. Can you let me know if it is correct?