Redesigning garden with a steep slope - what are my options? (pictures attached)

[sb1987]

Hi all,

 

I'm looking to redesign my garden. As you can see from the pictures, almost half the garden has a fairly steep slope which is wasted space. I also plan on extending the patio area because currently there is only enough room for a very small table and two chairs. The reason I want to flatten part of the slope is because otherwise there will be very little grass area left.

 

I'm aware a retaining wall will be required, and have toyed with the idea of a Gabion wall too. I'm also aware anything over 2m would require planning permission.

 

The slope runs all along the back (neighbours garden on the left, community car park on the right), so obviously the adjoining ground height difference on either side will need to be accounted for if the slope is removed. Another option is a stepped slope, but again, my priority is to extend to flat grass area as much as possible.

 

I'm sure this could be a considerable amount of work and some of you may suggest to just plant shrubs/trees at the back, but this is something I really would like to have done to maximize the usable space. Even cutting the grass on the slope is hard work, currently. 

 

Does anyone have any suggestions? Or a very rough idea how much something like this would cost (I know it's hard to say) - I hoping for it to be £10k or less.

 

Many thanks.

 

[Conor]

What is access like for machinery? Could you approach the owner of the communal space about access? One of your biggest costs will be digging and mucking away.  Because of your limited space you will want reinforced concrete retaining walls along the boundary edges at least. I'd budget £1k/m for the walls.l if they are over 1m. There are other more cost effective option, like interlocking blocks. From reading here, gabions aren't the most cost effective unless you have cheap / free infill and can do labour yourself. 

 

Is there scope to raise the height of the existing lawn? E.g. you can lose almost all of the spoilings by raising the garden up and having a small wall at the patio end. 

[patp]

Be aware that, if you put steps in, you could devalue at selling time? People with disabilities and those with young children might find them off putting.   A long, curved, pathway, though, would be a rather nice feature winding its way down the garden.

[JohnMo]

Buy a pair short ski's or snowboard. Small dry ski slope?

 

We used 8" diameter posts to hold our bank back. Think they are 3M long, with a meter concreted into the ground.

.

[Wumpus]

It might be possible to create a couple of terraces and use the dig-out from the lower level to backfill the upper level behind some kind of gravity structure like gabions. Cartaway will be expensive so best avoided, especially as your access looks difficult. It will need some kind of excavator I would think, not something you would want to do by hand.

 

another option might be a criblock system which can look softer than gabions.

[sb1987]

1 hour ago, Conor said:

What is access like for machinery? Could you approach the owner of the communal space about access? One of your biggest costs will be digging and mucking away.  Because of your limited space you will want reinforced concrete retaining walls along the boundary edges at least. I'd budget £1k/m for the walls.l if they are over 1m. There are other more cost effective option, like interlocking blocks. From reading here, gabions aren't the most cost effective unless you have cheap / free infill and can do labour yourself. 

 

Is there scope to raise the height of the existing lawn? E.g. you can lose almost all of the spoilings by raising the garden up and having a small wall at the patio end. 

 

Hello,

 

The right hand fence backs onto the communal carpark. There is plenty of access for machinery. I have two dedicated parking spaces right next to the fence and the one builder that visited a couple of years ago mentioned access was very good. 

 

Interlocking blocks sounds like an interesting option. I will look into this further.

 

I also like the idea of raising the lawn height. I'm not bothered about steps potentially devaluing the property. We live in quite a high demand area, so can't seeing this putting off potential buyers in the future.

 

Thanks for your reply.

 

[sb1987]

2 minutes ago, Wumpus said:

It might be possible to create a couple of terraces and use the dig-out from the lower level to backfill the upper level behind some kind of gravity structure like gabions. Cartaway will be expensive so best avoided, especially as your access looks difficult. It will need some kind of excavator I would think, not something you would want to do by hand.

 

another option might be a criblock system which can look softer than gabions.

 

Thanks for your reply. Access is actually very good. The right hand fence backs onto the communal carpark and I have two parking spaces next to the fence. If the fence was lifted, machinery would be easily able to access the garden.

 

Kind regards

[Conor]

Having full drive in drive out access for plant is a game changer. A 5tonne digger will have the stripped back and trenches dug for retaining walls in a day. Another day to pour a base for the wall (assuming RC), another day of shuttering and a pour for the walls themselves. I wouldn't skimp on the retaining wall at the back as you've a fairly substantial slope above it, in these cases you are just retianing to the height of the wall, but the extra load coming "down" the slope when it's wet. You might want a structural engineer for peice of mind. Then final levelling of the ground and reinstating. £5-7k. You'd nearly double that if you only had padestrian access.

Edited June 5, 2023 by Conor

[sb1987]

Thanks @Conor,

 

May I ask what would you do if this was your garden? What ideas come to mind if you wanted to increase useable space and to improve the overall look and feel of the garden? I am open to ideas. Another person suggested three terraces with steps using retaining wall hollow blocks to make use of the waste soil you will be digging out.

 

Cheers!

Edited June 5, 2023 by sb1987

[sb1987]

Here are a few more photos to help vision the elevation. I would say the elevation from the flat turf to the highest point to be around 2m.

 

 

 

 

Edited June 5, 2023 by sb1987

[Temp]

If you dig out the full width you would most likely have to take out the fences both sides and build side retaining wall and reinstate the fences. How about leaving a meter of so either side sloping down and taper the retaining walls something like this. Gives you a recessed area near the "P" of "Plan" for a small BBQ or seating area. 

 

Not a great sketch sorry..

 

 

[sb1987]

That is pretty incredible. Thanks for sending that across!

 

I suppose that can also result in less need for patio area near the house, as there will be a seating area where the slope currently lies. 

 

Could your design be combined with tethered steps for the higher sections of the slope? 

 

And does a wall created in such a way (where there is a meter left on either side) have benefits i.e. less construction cost/effort?

 

I know it is hard to tell, with there being so many variables at play, but any idea in terms of how much something like this would cost?

[sb1987]

Also, does anyone have any experience with anchored retaining walls?

1. Would it be suitable and allow the slope to be removed back further?
2. Would an anchored wall be far more costly?
3. Would there be any options for the side slopes? (adjoining from neighbours side and community car park), since the force wouldn't be directly behind, could we get away with just sleepers and new fence?
    

Many thanks.

 

Here is a rough sketch:

Edited June 5, 2023 by sb1987

[Radian]

Have you considered steel piling? It could allow you to go nearly all the way into the bank. Then dig out and maybe build a garden room!

[Conor]

The size / type of retaining wall is highly dependent on the soil type. E.g. where I am it's a stiff red clay with high modulus meaning we have very tall and steep slopes with no additional retianing needed.

 

For what I'd do there, it depends what I want to get out of the space, and where the best spot for socialising is. I'd hate to be staring at a big concrete wall, so I'd be minimising that aspect. I'd probably extend the flat area a bit, raise it up, meaning a "sunken" patio, up 400mm to a flat lawn, going back to the bank which would then be a small number of low walled terraces. 

[Temp]

Not sure how accurate these costs are but they suggest £250 to £450 per square meter. 

 

https://www.checkatrade.com/blog/cost-guides/retaining-wall-installation-cost/

 

 

 

 

[Temp]

21 hours ago, sb1987 said:

does a wall created in such a way (where there is a meter left on either side) have benefits i.e. less construction cost/effort?

 

The main advantage is you might get away without having to take down fences and  dig out your neighbours garden temporarily while you build the retaining wall. That's one advantage of the sheet steel piling that @Radian mentioned. These can be hammered into the ground close to the boundary and then you dig out your side afterwards. 

 

Curved walls are inherently stronger than straight and look better in my opinion.

 

If you want to go back so far that the wall is over 1m high you should get a professional involved and they should be able to propose different design ideas and solutions.  

[sb1987]

On 05/06/2023 at 21:52, Radian said:

Have you considered steel piling? It could allow you to go nearly all the way into the bank. Then dig out and maybe build a garden room!

 

That sounds interesting. After a quick google search I remembered an estate nearby has used the same for their gardens where it backs onto a steep slope. 

 

Would this be considerable work and expensive? Would it be a solution for the neighbouring ground difference once the slope is dug out?

[sb1987]

14 hours ago, Conor said:

The size / type of retaining wall is highly dependent on the soil type. E.g. where I am it's a stiff red clay with high modulus meaning we have very tall and steep slopes with no additional retianing needed.

 

For what I'd do there, it depends what I want to get out of the space, and where the best spot for socialising is. I'd hate to be staring at a big concrete wall, so I'd be minimising that aspect. I'd probably extend the flat area a bit, raise it up, meaning a "sunken" patio, up 400mm to a flat lawn, going back to the bank which would then be a small number of low walled terraces. 

 

The soil in my area contains quite a bit of clay. Looking at a soil map, it's actually described as "loamy", but I know from experience there is quite a bit of clay in the slope, so much so that it's not uncommon for me to dig out big chunks of it.

 

[George]

 

On 05/06/2023 at 20:51, sb1987 said:

Also, does anyone have any experience with anchored retaining walls?

1. Would it be suitable and allow the slope to be removed back further?
2. Would an anchored wall be far more costly?
3. Would there be any options for the side slopes? (adjoining from neighbours side and community car park), since the force wouldn't be directly behind, could we get away with just sleepers and new fence?
    

Many thanks.

 

Here is a rough sketch:

 

What is the wall at the back - it looks a bit more substantial than a fence...? Is it also a retaining wall? Beware doing any new retaining works that could undermine the foundation it

 

Anchor systems are good but you will need to stay within your property boundary. 

[bgmill]

I would be inclined to cut a seating area into the hill, like a half-sunken fire pit enclosed on 3 sides.

 

 

[oldkettle]

A general observation. Get a laser level and measure the actual fall, you can easily do this in the evening. I was surprised to find out that our slope, which doesn't look steep from the house, is over 3m overall. 

[sb1987]

11 hours ago, George said:

 

 

What is the wall at the back - it looks a bit more substantial than a fence...? Is it also a retaining wall? Beware doing any new retaining works that could undermine the foundation it

 

Anchor systems are good but you will need to stay within your property boundary. 

 

No, it's just a regular fence, although a little more bulky than a traditional, most likely to reduce noise. It backs onto a dual carriageway which is about 10 meters behind where it stands. There is no current retaining features, just a slope with a fence above it.

 

Looks like an anchor system wouldn't be an option them  

Edited June 7, 2023 by sb1987

[sb1987]

11 hours ago, bgmill said:

I would be inclined to cut a seating area into the hill, like a half-sunken fire pit enclosed on 3 sides.

 

 

 

That looks nice, but I believe will still need a form of retaining wall to encircle it. 

[Temp]

On 06/06/2023 at 22:02, sb1987 said:

 

That sounds interesting. After a quick google search I remembered an estate nearby has used the same for their gardens where it backs onto a steep slope. 

 

Would this be considerable work and expensive? Would it be a solution for the neighbouring ground difference once the slope is dug out?

 

Yes the sheet steel piling serves as a structural retaining wall.  If you don't like the look you can add non structural timber cladding or planting to hide it.  

 

 

While googling for a picture I found there is also PVC sheet piling but not sure if available in the UK.

 

https://www.escpvcsheetpiling.com/retaining-wall