Drainage

[71-1093879278]

Please help.
I have designed a patio which sits up against a plinth of a house wall. The plinth is roughly 150mm wide out from the house & looks to be housing several pipes and drains).
Firstly, my idea was to build a raised patio & so not to compromise the DPC my intention was to build up against the plinth but leaving say a 10mm gap between the raised patio & plinth (the width of the plinth and the 10mm gap to be filled with hanging planters etc). Is 10mm enough to allow rainfall drainage off the plinth and essentially down the back of the patio?? Will the back wall of the patio (300mm high) need a DPC?

Does anyone know if these plinths have to remain? Can I instead get rid of it exposing pipes etc or is there a reason for them?

Hope this makes sense!! :)

[84-1093879891]

I'm having trouble visualising this - you have a 150mm wide plinth against the house; is this concrete?

So, you patio paving stars 150mm from the house, but you;re planning to raise the paving level to avouid conflict with the dpc - how does that work? Surely the dpc is already 150mm above the plinth level, isn't it?

Then there's this 10mm gap that you plan to fill with planters? 10mm - that's the width of a typical joint in flag paving - how can such a relatively narrow gap be filled with hanging planters?

And then you're hoping that this 10mm gap will provide drainage. I'm not sure whether it would, but there's a very good chance that it would silt-up in next to no time.

Can you try to explain the layout again? Or could you post/send in a sketch to help me visualise the problem?

[71-1093879278]

Sorry for the confusion!

OK. So we have the house wall & built against this wall is the plinth. The plinth is 180mm high and 300mm wide (slight change from original post, apologies). The plinth is all boxed in by bits of random stone with holes in the top of plinth allowing for downpipes etc.

Now so as not to compromise the plinth or house wall at all, I thought of building the raised patio up to the plinth with say a 10mm gap between the edge of the plinth and the back of raised patio. Therefore there'd be 310mm between the actual house wall and the patio (patio to sit about 300mm high). The planter troughs I envisaged would be attached to house wall and the point of these is to distort the huge 310mm gap between the house and patio.

Rregarding drainage, I was concerned whether a 10mm gap between the edge of the boxed plinth and the patio would compromise drainage off the plinth and onto the ground.

Alternatively, my ideal solution would be to get rid of the plinth and deal with the DPC by building right up to the house wall and leaving a 100 - 200mm gap.

Is this making more sense??!! I hope so :)

[84-1093879891]

Summat like this....???



...where does the dpc lie? Above the top of the plinth?

I really can't see that 10mm gap working as an effective drain for more than a year. It will silt-up in next to no time, and there's no guarantee that the sub-grade would be able to deal with all the water being directed there.

[71-1093879278]

That's exactly it!
The plinth lies just below the DPC.
From what you understand, do you think I could just remove the plinth? It's a hefty structure stopping my patio from being as close to the wall as possible!
And all I can see its purpose for, is housing drains & host of drain & out pipes. Could it be that someone wanted to hide the pipes etc and create a seating / bench arrangement out of it??

[84-1093879891]

I never know what goes through folks' minds when they do this sort of thing, but the presence of that plinth just below dpc is worrying, and, if it were me, I'd rip it out and have a re-think while i'm doing the patio.

If a job's worth doing....and all that. I can't see the point in making all that extra work for yourself when it's highly likely that the plinth is a bit of nonsense that can be eliminated with a bit of commonsense plumbing or drainage installation.

[71-1093879278]

Thanks for all your advice Tony.

Hope you don't mind a design student asking what may be obvious questions to those in the trade!!

:)

[84-1093879891]

I don't mind at all - it's only by answering such questions that I can learn which parts of the site need expanding or clarifying, so it's a mutually beneficial arrangement. :)

[danensis]

Siily question here - this "plinth" isn't the edge of the foundations is it? In which case Kangoing it away might not be a Good Move.

[84-1093879891]

Not if it's only just below the dpc and dressed in stone on the external edge, but I know what you mean, Jon.