Concrete Hardstanding

[JoshRogan]

Right, as usual I have had a look around and cannot find anything to quite match my question!

I have an existing hardstanding which is now the base of my garage, which I have built up around it. The hardstanding has a slight slope on it allowing water to 'flow' into the garage rather than encouraging it to stay outside, so I intend to concrete over the existing to correct this.


Looking on paving expert website hardstandings should be 100mm thick minimum, the existing hardstanding meets this requirement.

My question is, I want to put a DPM down and then concrete over the top, should this new concrete be minimum of 100mm thick too or can it be slightly thinner due to the 100mm existing beneath it?

I'm not sure if the DPM will upset the characteristics or wont make the blindest bit of differece, hence the question.

many thanks.

C.

 

[JerryM]

1st thought is it seems a lot of effort. why not cut out a trench of the concrete along the front of the garage and fit/mortar in a proprietary channel drain (something like screwfix 95012).

as far as i know the 100mm thickness is to give good durability for heavy usage (ie cars) but the thickness depends to a large extent on how good the sub base is. i've seen hard standings for cars 50mm thick in good condition but clearly the sub base must have been pretty good.

in terms of dpm what would be it's purpose as it would be unusual for a garage.

if you need a dpm then i am thinking that a liquid dpm might be best (to minimise the thk of concrete or screed). with a sheet dpm i think it would be tricky to bed it down onto the existing concrete to achieve a consistent support for the new base. i would go for 50mm for the new concrete base.