Shed base on existing concrete slab - advice please

I am going to replace my current shed which sits on a concrete pad. This pad has a slope on it and is larger than the shed. The shed has "moved" out of square due to the slope and has suffered with rot on the lower tongue and groove planks due to a combination of rain splashing up and the runners sitting on the concrete.

The guy supplying the new one, which will be very heavy duty and 10 feet long by 6 feet wide, has confirmed the base needs to be completely level and either the exact foot print of the new shed or just a couple of inches larger. I have some solid concrete blocks which are 440 x 215 x 100mm. I would appreciate any opinions regarding whether the base should be a complete pad of blocks or if I should lay them in individual rows, with narrow gaps between the rows, to allow rainwater to flow down to the drain at the front of the new shed.

Any recommendations regarding whether the base is better to be an exact footprint or have the extra couple of inches around it?

May I also ask for opinions as to whether I should add a damp proof membrane to the top side of the laid blocks so the shed floor sits on this?

Thanks in advance,

Tracey

Try and get a look at the shed base. The floor will be supported by mini joists which must be supported. So draw out the outline of the shed base on your concrete, mark in the joists. With mortar and your blocks put in supports with a level top. They need not be continous, but closer together the better. Put your damp course material on top of the blocks/mortar.
Frank

Hi Frank,

Many thanks for your reply and the information provided. I am pleased I was thinking along the right lines and I appreciate the suggestions you have made; I will certainly take them onboard.

Kind regards,

Tracey

I have decided against laying these blocks myself as they are too heavy for me to handle with ease. Would anyone be willing to give me an idea of what I should expect to pay to have them laid please?

Just to recap; it will need to be a level, 10 foot x 6 foot rectangle, laid on an existing concrete pad which is sound but not suitable to put the new shed on as it has a slope on it for drainage.

Thanks very much,

Tracey

You can use bricks of course, you just need more of them.
Frank

Hi Frank,

Thanks for the reply. I am keen to use the blocks as I already have them but thanks for the suggestion.

Kind regards,

Tracey