laying a patio on clay soil and dpc issues

[dajo]

Hello folks,
I'm laying a patio which I wan to adjoin the house. To get the necessary slope (1:60) the surface of the patio will need to be less than 150mm from the dpc - about 100mm is the best I can do. Also the ground is heavy clay soil. The patio is to be 4m x 3m.

Here's my questions:

1) Is it "legal" to have less than 150mm (eg 100mm) below dpc if a linear drain is put between the patio and the house?
(as suggested in http://www.pavingexpert.com/dpc01.htm)

2) Do I need to build it on hardcore, or is sand enough?

Many thanks - and sorry for the novel!

Dajo

 

[noseall]

the 150mm below dpc rule is to do with water ponding or splashing against a building, and if contravened water can supposedly saturate those bricks above dpc.

i have known building control accept a lead flashing chased into the mortar joint above the damp course, in a situation where 150mm could not be achieved. this was due to a neighbouring property being higher up the slope on a run of terrace houses.

 

[Thermo]

the alternative is to leave a 4" margin along the side of the house and fill it with a free draining materail ie gravel etc.

For the umpteenth time build it on a bed of compacted MOT type 1 stone chippings and wet lay the slabs on to that.

 

[dajo]

thanks for that!

I was looking at the
Hepflow linear drainage () - do you think this would be suitable alongside the house at, say 100mm below the dpc? (it's 5 1/2 inches wide)

Cheers...

 

[ModernMaterials]

you may think my attitude somewhat cavalier but i think 100 mm is adequate.

you have already stated that the patio will fall away from the structure. Splashback on to the brickwork is unlikely to be a problem.

as far as i am aware, you are not obliged to inform building control about your patio so i dont think legality comes into it ( it certainly wouldnt in my world after all i would be monitoring it and the first sign of damage i would be changing things...)

people do much worse things to buildings than you are proposing. Stacking things up next to external walls, for example, would potentially cause more damage.

i wouldnt bother buying that linear drain to remedy this either unless you have water that has no where to go.

in short, as long as water is draining away from the building and you are aware of and monitoring possible negative aspects, then go ahead with your original plan.

 

[Thermo]

not cavalier at all, we do it all the time and bco been happy with it when theyve been involved.

 

[dajo]

thanks for that everyone - the job's well underway now thanks to your advice

 

[WabbitPoo]

My BCo told me that the 6" rule is only applied to new builds now - its not a buidling reg issue for new patios. I think splash back is an over-rated "problem".