How to prepare an existing concrete slab for a prefabricated shed?

[doberon]

   

I'm wanting to built a 3x3 prefabricated shed on an existing concrete slab. The slab is much larger than required for the shed (approximately 4.2x3.4) so I'm worried about potential flooding. 

The slab is not level due to a a series of cracks - likely caused by a tree root - and so I'm wondering what my options are. 

I figure pouring a rebate will be an expensive and time-consuming project that, given I'm not rectifying the cause of the crack in the current slab, may degrade quickly. 

I'm interested in fixing the shed to the existing slab and building a floor as per @MitchellMc  guide how to install a shed floor.

However, I want to ensure the part of the slab the shed sits on is level. Could I build up a 3x3 form and pour self-leveling compound to achieve this as suggested in @MitchellMc post how to level a cracked outdoor slab?

Thanks. 

[MitchellMc]

Hi @doberon,

Typically, you'd run the board perpendicular to the joists. The tongued side needs no extra support, but the ends should finish midway on a joist. If this is impossible due to your configuration, a support or noggin must be installed under the non-tongued join, or it will flex.

Great work so far!

Mitchell

[doberon]

Thanks, @MitchellMc 

I planned on running the boards perpendicular to the joists and cutting them to size so they end on the joist - the base is only 3050mm wide so only one board wide. 

I’ve added noggins halfway down the joists to account for some warped joists (approximately 1500mm) but it’s good to know I won’t have to add another two rows.