advice for sub-base and concrete slab

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hi all,

i would like some advice on creating a sub-base for a concrete slab for a workshop i would like to build at the bottom of my garden.

the area where the slab is going is overrun with grass and weeds at the moment. i was wondering if it would be acceptable to strim all the grass and weeds away then kill it all with something like roundup.

once its all dead, put 50-75mm of MOT down and wacker it flat and level. i am not going to be doing the slab for about a year because of money and other jobs.

would this be long enough for everything below the MOT to rot and settle so that my slab would have a better chance of not moving or cracking?

just in case its needed the finished size of the slab will be 7.4*3.5m and the MOT will be 0.6m wider all round except at the front which will be 0.2m.

also what thickness of concrete would be recommended and any ideas of a rough price for premixed wheelbarrowed in concrete.

any advice would be greatly appreciated.

cheers

 

[noseall]

You need to dig off all fertile matter. This is usually a case of removing 200mm - 300mm of material from the surface.

Don't bother doing it until you are ready to build the base, otherwise it will be overrun with weeds again. Seeds will just settle in the mot and germinate.

An accepted minimum hard core layer is 100mm as is a standard concrete slab. You may need to thicken the slab at the edges forming a 'toe'.

You will need about 2.7m³ of concrete to form a 100mm slab at the sizes you stated.

 

[tony1851]

Don't forget to put a dpm under the concrete - not mandatory but if you have wet ground, it would help keep the slab drier.

 

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thanks for the help. sounds like i have more work than i wanted. may have to byte the bullet and do it in one hit then.

i am not sure if i have mislead you or if it makes any difference but the workshop will be more of a large shed for hobby work and storage. there will be nothing like vehicles etc. the largest thing in there out probably be a small center lath and the building would be made out of timber.

dont know if it makes a difference or not and thanks again

 

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also how did you do the calc for the amount of concrete needed?
i thought it would have been 8.6*4.3*0.1=3.7
is there a percentage or value that needs to be applied to the calc that i dont know about?

thanks again

 

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oops ignore the one about calcs i read the wrong thing from my own notes