Advice on installing a patio in a sloped garden?

pinkcloud17

I am in the process of getting quotes from landscapers to have a patio installed in my garden.

Currently, my garden consists of turf on a fairly steep slope towards the house. The house is a new build so I'm guessing the soil quality is poor and is mainly clay based.

My house has air bricks near ground level with a section of gravel between the grass and the house (see photo). I don't know what is underneath this gravel.

I would like the section directly beside the house excavated and levelled for the patio, with the rest of the grass behind the patio remaining on a slope towards the house and retained with a timber wall.

One landscaper has told me having the gravel section around the house will be sufficient for drainage which I am unsure of. He has said he could also install a drainage channel in front of the gravel to reassure me but I don't think this would look good. I am guessing the gradient of the patio in this case would be slightly sloping towards the house.

The second landscaper has told me in no circumstances should you slope a patio towards a house and he has said he would create a gravel border in front of the retaining wall in the middle of the garden and slope the patio slightly towards this. My concern is this means the middle of the garden would be receiving drainage from both the grass on one side sloping towards it and the patio on the other also sloping towards it from the other direction. He is quoting £2000 more than the first guy. He also said he would recommend raising the patio to the lip of my patio door which I'm a bit concerned he would suggest as this is above the DPC.

My questions are:
Do I need extra drainage i.e. a channel drain or is a gravel border sufficient?
Should I have the patio sloping towards the house or towards the new retaining wall? 

Please can anyone advise on this? Thank you  
 

FreeBear

A patio should always slope away from the house and be 150mm below the level of the DPC. Depending on the area of the patio, you could have some SUDS crates buried in the ground linked to drainage along the edge of the paving. How big the SUDS crates would have to be would depend on soil conditions and the area being drained. Unfortunately, this is going to push up the cost.

You might want to reconsider the use of timber for a retaining wall - Unless done right, the timber could rot away in less than 10 years. How high is this retaining wall likely to be ?

pinkcloud17

@FreeBear thank you for your reply. I have been reading a lot of varying advice but the patio running away from the house does seem to be the best thing to do. 

I am not sure where my DPC currently is. A third landscaper I have had to quote is now making me completely confused as to what to do. As he has said the gravel is currently above the DPC. What he would do would be remove the gravel border completely and have an aco channel running along the house with the slope running towards it. So all three landscapers would do completely different things with the drainage and now I'm stuck. 

Due to the air bricks, surely doing the above option would mean lowering the patio ground level significantly compared to what my small door patio currently is. Meaning it might need an extra step between the patio and the path/grass.

I will have a think about the wall, thank you for pointing that out.

pinkcloud17

@freebear also regarding the SUDS, not sure that would work as the soil quality is likely to be poor/ clay based due to being a new build

Bendy_House

The DPC is surely where the 'dashed wall meets the bricked part? In which case, it's not below gravel level.
The VENTS are, tho', so they need to be kept clear as they currently are.
How much 'slope' are you talking about, Pink, if you were to level that grassed area out to the edge of the new patio? What actual depth would be needed on the outside edge - what height of soil beyond this would need to be retained?

The current line of gravel, could you 'excavate' this towards one end and see if it leads to a soakaway drain? Ie, just lift out the gravel for a looksee, that's all. Or, have you a copy of the build plans, or can you look them up online (say on your LA's Planning Portal - I think they should show detail like drains and soakaways).
During heavy rain, have you ever seen surface water showing on this gravel?

Section62

pinkcloud17 said:

I will have a think about the wall, thank you for pointing that out.

Ideally timber should only be used for decorative purposes, not for retaining any substantial amount of ground.  It is cheap and quick to install, which is why landscaping companies love it... but they will be long gone by the time the inevitable problems start. There are timber retaining products, but the quality of wood and treatment process is controlled to a higher standard than (e.g.) sleepers from a DIY shed.

It would also be a good idea to check the planning consent for your property/development - there may be planning conditions or removal of PD rights relating to alterations to the landscaping, particularly the creation of (larger) impermeable surfaces and/or adding runoff to communal/public drainage systems.  There may also be covenants requiring consent from the developer and/or others if you want to make changes. (changing the ground level in your garden is likely to have an impact on the neighbours, it could lead to 'tensions')

Section62

Bendy_House said:

The DPC is surely where the 'dashed wall meets the bricked part? In which case, it's not below gravel level.

It should be just below the weep vents - so probably along the joint at the top surface of the gravel.  Judging from the embedded 'gravel board' on the fence to the left I'd guess the OP's garden level has been raised since original construction (or the planned FGL).

pinkcloud17

Bendy_House said:

The DPC is surely where the 'dashed wall meets the bricked part? In which case, it's not below gravel level.
The VENTS are, tho', so they need to be kept clear as they currently are.
How much 'slope' are you talking about, Pink, if you were to level that grassed area out to the edge of the new patio? What actual depth would be needed on the outside edge - what height of soil beyond this would need to be retained?

The current line of gravel, could you 'excavate' this towards one end and see if it leads to a soakaway drain? Ie, just lift out the gravel for a looksee, that's all. Or, have you a copy of the build plans, or can you look them up online (say on your LA's Planning Portal - I think they should show detail like drains and soakaways).
During heavy rain, have you ever seen surface water showing on this gravel?

Thank you so much for your reply. The height of the retaining wall would be roughly up to knee level (sorry that isn't very precise!).

I didn't get given a copy of any building plans. I might try lifting up the gravel and take a look. 

Never noticed any surface water sitting on the gravel, they just get damp during heavy rain but do dry out.

pinkcloud17

@Section62 thank you I will rethink the timber wall. 
Never even thought about those other things, I may need to speak to the site manager to check, thank you.

pinkcloud17

@Section62 My garden hasn't been changed since construction, that is part of my neighbours patio they have put in

Section62

pinkcloud17 said:

My garden hasn't been changed since construction, that is part of my neighbours patio they have put in

Yes, I meant it was either a post-construction change, or they've made the garden up to a different height (Finished Ground Level) to that originally planned.  You'd hope they hadn't planned to make the garden the same level as the DPC.