Drainage for patio needed?

[doingitmyself]

Hello everyone... with nice weather finally here I'll finally be building my patio next week.

 

For info...
- we have recently had an extension done; only 1.4m at the back where you can see the bifolds.
- the old patio was destroyed of course
- old patio did not have any drainage and we have had zero issues. Even with all the rain we've had in the last few weeks (in Berkshire), water drains away well.

 

I am raising the base slightly to create a new patio so the floor level from inside to outside isn't too large. The distance below the DPC will still only be 90mm. I know the recommendation is 150mm, but PavingExpert says as long as the fall is 1 in 60 away and the paving sits under the sill, that's fine.

 

What about the walls on either side of the bifolds? I've attached some pictures - please ignore the rubbish. It's a 19m2 square patio.

 

There is currently a bed of sand (I think) on top of concrete base.

I'll be back filling 150mm of type 1 using wacker plate, then 30mm mortar (6 part sand:1 part cement), topped with 20mm porcelain slabs, with the 1 in 60 fall.

There is a gutter drain on the far right where I could run a slot drain, but if I don't need to, I'd rather not.
 

[Mr Punter]

First off, what's with the footwear display?

 

Regarding drainage, if there were no issues before there should be none now.  Best have a fall away from the house.

 

I would be tempted to leave a 100mm wide channel against the walls and fill with pea gravel in case the walls get saturated above DPC with splashes but it depends how exposed they are.

[Big Jimbo]

As above 100 gap where it meets the building, and pea gravel. Even some other fancy stone if your feeling flush.

[George]

Agree re the gravel strip. Maybe 150mm against the side wall - line it up with the size of the gulley.

 

By the book.... you should slope down to get to 150mm below DPC once past the door. However it's a relatively short length until you hit the fence so you'd just make it hard to use (as it'd be sloping and directing water to your neighbour). So I'd keep is level against the wall with the doors and slope uniformly away to the garden. 

 

You could put in a channel drain at the bottom of the patio as it'd be easy to direct it into the gulley pot. But if it's pretty free draining soil that's not really necessary. My soil goes a bit soggy immediately next to the patio but it all slopes away.

[ToughButterCup]

54 minutes ago, Mr Punter said:

First off, what's with the footwear display?

...

 

Partner hit him with the rolling pin once too often because of wet feet traipsed all over the living room carpet: hence the question about drainage. 

 

No @doingitmyself, a well drained patio will not dry your trainers enough for you to be able to waltz all over the super clean carpet without drying your feet.

To answer your question : 1:100 - maybe 1:60ish - fall, gravel strip to suit, and an easy to clean door mat.

 

Then treat yourself to £20's worth of pure joy .

?

Edited June 2, 2021 by ToughButterCup

[doingitmyself]

Was trying to avoid the 100mm gravel gap as not too keen on the look, but better safe than sorry!

 

Will absolutely splash out on that beautiful mat.

 

Thanks all.

Edited June 2, 2021 by doingitmyself