Patio pooling in heavy rain

Patters1978 · 8 May 2021

Hi

DIY patio job by myself lol
Anyway Indian sandstone patio laid on 100mm mot 1 then 4-1 solid base.
Patio falls into an area where artificial grass will be going now the patio is in a L shape around the grass area so the fall obviously goes away from the house but also at the end of the L I have made it fall away from the summerhouse at the bottom of the garden.
It kinda dishes around the grass area.

Now before yesterday when I laid the sand ready for the grass the water would gather at the lowest point of the dish in heavy rain but would be draining into the grass area once the rain stopped the patio would naturally drain off without much standing water left behind.
In the grass area it would pool a little before finally draining off in the low spots of the mot 1
Yesterday I levelled and flatten off the mot 1 and added 30mm of sand on top of the 50mm mot 1, woke up this morning to heavy rain and the area that normally gathers and pools off is much larger! And pooling all around the grass area! I still think it's pooling off but has more resistance now the grass area is levelled to the patio.

So I thinking of adding a soak away in the grass area around the border of the patio and filling with pea singles to help with drainage?

Help lol

Munroast · 8 May 2021

this is what I done with ours to stop the water pooling at the edge of the grass, the gravel area even has the capacity to take all the water when power washing. And I think visually it looks better, but obviously that may just be a matter of opinion.

Patters1978 · 8 May 2021

Munroist said:
this is what I done with ours to stop the water pooling at the edge of the grass, the gravel area even has the capacity to take all the water when power washing. And I think visually it looks better, but obviously that may just be a matter of opinion.

Yes it does look nice but not the look I was going for we have put cobbles around the border of the patio.

Before the sand has gone into the grass area it seemed fine like I said it would gather in the lowest pinch point at the edge of the grass but now seems to gulf a large area around the grass.

I'm unsure if this is normal during heavy rain and it's expected or something I need to fix

In the photo under the uncut grass (placed on top to stop dog digging up sand) the border curves normally it would just gather there but now is gathering as you can see in the photo a larger area.

Patters1978 · 9 May 2021

So yesterday I start to dig a trench out and this morning awoke to the attached photo!

Before the grass went down nothing like this happened at all,. I'm lost for words right now!

What the hell do I do

Munroast · 9 May 2021

What is the sub base of your garden - are you on clay for instance ?
I take it water can easily flow through the plastic grass ?

you could form a soak away somewhere and create a drain to it (might be difficult stopping the entrance blocking up or the soakaway silting up. I built one in a troublesome area in my garden (sorry no pics) it is basically a 2 x 2 x 2 foot cubic void with a paving slab on top then soil and grass, an area that used to have standing water in wet weather now doesnt. it all drains through gravel so very unlikely to silt up for many many years.

Patters1978 · 9 May 2021

Munroist said:
What is the sub base of your garden - are you on clay for instance ?
I take it water can easily flow through the plastic grass ?

you could form a soak away somewhere and create a drain to it (might be difficult stopping the entrance blocking up or the soakaway silting up. I built one in a troublesome area in my garden (sorry no pics) it is basically a 2 x 2 x 2 foot cubic void with a paving slab on top then soil and grass, an area that used to have standing water in wet weather now doesnt. it all drains through gravel so very unlikely to silt up for many many years.

Yes I dug through clay in the trench.

I'm thinking i complete the trench then dig another trench towards the middle of the grass area, then a hole with some hardcore lay some pipe to transfer the water to the bigger hole in the center?

The grass said it was permeable and does have holes in it.

I just don't get it before laying the sand it didn't pool as bad as this probably about a cm pools in places where the mot1 dipped?

Patters1978 · 9 May 2021

Just for point of reference I didn't dig much of a trench last night, I've just got the water out of it see picture

Patters1978 · 9 May 2021

Also I've dug down even more to soil and the odd house brick and large pebbles lol
House is newish build 10ish years

Munroast · 9 May 2021

what type of sand did you use ? sharp or soft

Patters1978 · 9 May 2021

Sharp

Patters1978 · 9 May 2021

Keep digging and it's just clay.
A lot of the clay/dirt was dry under that big puddle

Patters1978 · 9 May 2021

Finished trench and just moved dirt and hosed down patio I'm about 40cm down so far still clay and water don't seem to be shifting

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Patio pooling in heavy rain

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