Do I need a fall here?

[machtucker]

Hi everyone,

 

Well the weather is looking to be better next week and I'm on leave so planning on doing a bit more landscaping in the garden. I'm going to excavate the bottom part of the garden (bounded by the yellow line in the model). There is a clay paver path to be laid on top of sharp sand bedding layer and also 6mm gravel in the other areas with a stabilisation layer and 10-15mm bedding layer of sharp sand. I'm planning to use a 100mm MOT Type 1 subbase layer for the whole lot.

 

The question is should I put a fall on it or will it be OK level for drainage purposes?

 

Many thanks,

 

Ed

 

[ProDave]

Compacted MOT1 does not drain well, so don't expect water to drain through it quickly, so a fall would make great sense.

[markc]

As above, Type1  holds water, if it’s under a drive or garden area, road plannings compact very well and drain well too.

[saveasteading]

18 minutes ago, markc said:

road planings compact very well and drain well too.

They shouldn't if well mixed and compacted. A road is a mix of stones not unlike MOT I , but stuck together by a glue of bitumen.

If it is supplied as all big stones then it will have gaps and drain. If it is footpath material or surface dressing, then it is weak but solid.

 

I think the best of it goes back into new road surfacing these days, and the rest is sold off. 

4 hours ago, machtucker said:

a clay paver path to be laid on top of sharp sand bedding layer

So its best to lay the base to a fall and try to keep the sharp sand depth consistent . And it will be easier to lay.

 

 

 

 

 

[machtucker]

On 16/04/2024 at 15:58, saveasteading said:

They shouldn't if well mixed and compacted. A road is a mix of stones not unlike MOT I , but stuck together by a glue of bitumen.

If it is supplied as all big stones then it will have gaps and drain. If it is footpath material or surface dressing, then it is weak but solid.

 

I think the best of it goes back into new road surfacing these days, and the rest is sold off. 

So its best to lay the base to a fall and try to keep the sharp sand depth consistent . And it will be easier to lay.

 

 

 

 

 

Yes that's how I will do it, just like I did with the patio. I was wondering whether I could get away without a fall though. I did read something on Paving Expert website that talked about a suds compliant solution which requires a different subbase with fewer fines.

Edited April 17 by machtucker

[machtucker]

On this topic does anyone know where I can buy MOT Type 3 aggregate from? Doesn't appear to be as popular as Type 1

[saveasteading]

55 minutes ago, machtucker said:

where I can buy MOT Type 3 aggregate

It is crushed stone without the fines. Type 3 is a particular grading and uncommon. You could get a lorry load more easily than a bag.

A builders' merchant will have single size stone in big bags, with more or less variety according to local fashions. 

It can be expensive though  when it is made from attractive stone for paths etc. I bought some last week called Cotswold stone (It is white and will be exposed) for £78 / bag whereas the sharp sand or gravel  on the same delivery was £42.

If there is a local stone then this should be cheaper.

 

As it happens, it is for laying inside gravel grid specifically to be free draining.

The original went in about 15 years ago and has had a lot of use. We are cleaning the messy top off and releveling some areas. Because of erosion it is not open textured any longer and it puddles locally where it has dropped. But because it is on a slope, any that doesn't make it downwards will run off because of the slope. Then it is caught in a perimeter layer of gravel and french drain..

To summarise. Single size stone or gravel is SUDS in itself as long a it is deep enough, to hold the rainfall, and contained . A slope is up to you, but where would you then catch any runoff?

[machtucker]

20 hours ago, saveasteading said:

It is crushed stone without the fines. Type 3 is a particular grading and uncommon. You could get a lorry load more easily than a bag.

A builders' merchant will have single size stone in big bags, with more or less variety according to local fashions. 

It can be expensive though  when it is made from attractive stone for paths etc. I bought some last week called Cotswold stone (It is white and will be exposed) for £78 / bag whereas the sharp sand or gravel  on the same delivery was £42.

If there is a local stone then this should be cheaper.

 

As it happens, it is for laying inside gravel grid specifically to be free draining.

The original went in about 15 years ago and has had a lot of use. We are cleaning the messy top off and releveling some areas. Because of erosion it is not open textured any longer and it puddles locally where it has dropped. But because it is on a slope, any that doesn't make it downwards will run off because of the slope. Then it is caught in a perimeter layer of gravel and french drain..

To summarise. Single size stone or gravel is SUDS in itself as long a it is deep enough, to hold the rainfall, and contained . A slope is up to you, but where would you then catch any runoff?

Thanks for the info. I had planned everything without the fall on the lower level but it could be done. There is already an existing French drain which I’ve highlighted in a blueish colour, so I could put a fall towards that. Or… I could just make it level and see what happens 😬

[saveasteading]

1 hour ago, machtucker said:

make it level and see what happens

do it very thoroughly then, as the slightest dipping will allow puddling.

Or if your single size stone is deep it might hold all the rain. Just remember that only about 1/3 of the volume is voids if it is single size, or 1/4 if there is some variation..