Unfeasibly large retaining wall
Discussion
Hello all, I'm hoping someone here knows about this sort of stuff. A preemptive TDLR is that I'm in the early stages of mulling over thinking about getting a retaining wall built which would be approx 5 metres high by around 15 metres wide.
Around half of my back garden is a fairly steep slope which is essentially unusable and I fancy at some point putting a whacking great retaining wall at the end and levelling the garden. Due to the slope of the land the back garden is around one metre lower than the front as well, with a retaining wall separating them. The house is all at the front garden level, so I also want to raise this to make them match, or almost match at least.
From a very quick google it looks like a reinforced retaining wall would be the way to go rather than a poured concrete one. Does anyone who knows such things have any other thoughts. Also, I expect the costs to be eyewatering but what do we reckon a ballpark figure might be (excluding the infill material, I can get that for free.)
P.S. This is my first time on PH in about 15 years, I used to be such a lurker. Delighted to see the formatting stuff is all the same, now I'm going to go have a wander around and see if any familiar names are still around to give me a whack of nostalgia and then look for an update on the nazi garden bunker on Jersey.
Around half of my back garden is a fairly steep slope which is essentially unusable and I fancy at some point putting a whacking great retaining wall at the end and levelling the garden. Due to the slope of the land the back garden is around one metre lower than the front as well, with a retaining wall separating them. The house is all at the front garden level, so I also want to raise this to make them match, or almost match at least.
From a very quick google it looks like a reinforced retaining wall would be the way to go rather than a poured concrete one. Does anyone who knows such things have any other thoughts. Also, I expect the costs to be eyewatering but what do we reckon a ballpark figure might be (excluding the infill material, I can get that for free.)
P.S. This is my first time on PH in about 15 years, I used to be such a lurker. Delighted to see the formatting stuff is all the same, now I'm going to go have a wander around and see if any familiar names are still around to give me a whack of nostalgia and then look for an update on the nazi garden bunker on Jersey.
Research Marshals Redi-Rock retaining walls. I have done quite a few and they can look really good. Assuming you can get access with machines then they are easy to do and work well at your sort of height and length. Generally significantly cheaper than reinforced poured concrete or similar.
5 metres / 16 feet will require a VERY substantial wall - industrial spec. That’s the eaves height of a two-story house. It will potentially be holding up a vast weight. Is it just soil? You’ll need huge foundations and good drainage.
Have you thought about terracing? Several smaller walls will be a lot cheaper and easier than one great monolithic wall (and probably easier on the eye too)
Have you thought about terracing? Several smaller walls will be a lot cheaper and easier than one great monolithic wall (and probably easier on the eye too)
Thanks for the replies already folks, Redi-Rock was noted on my cursory Google, I'll look more into that.
To provide more info which may be helpful: There is no issue with machinery access at any point around the back of the house, it's all fields.
To help visualise it, the house is on a hill which slopes 100m down to the sea around 800m away, with the house essentially being on a nubbin on the hill, hence the relative steepness of the back garden compared to the surrounding land.
I know nubbin won't be the right word but I'm hoping it gets the layout across.
To provide more info which may be helpful: There is no issue with machinery access at any point around the back of the house, it's all fields.
To help visualise it, the house is on a hill which slopes 100m down to the sea around 800m away, with the house essentially being on a nubbin on the hill, hence the relative steepness of the back garden compared to the surrounding land.
I know nubbin won't be the right word but I'm hoping it gets the layout across.
I know people who've got more than 5m tall unsupported, near-vertical rock faces in their gardens.
Holding back a 5m bank of loose soil is very different from the same amount of half-decent rock.
Many things will be in between.
We've had a few little landslides around here in the past few years.
A large retaining wall would not be something I'd choose to buy into.
Holding back a 5m bank of loose soil is very different from the same amount of half-decent rock.
Many things will be in between.
We've had a few little landslides around here in the past few years.
A large retaining wall would not be something I'd choose to buy into.
For 5m you need proper assessment of ground conditions and then a set of properly engineered drawings. You will also need planning permission as it’s over 2m high.
Depending on what you can do with the spoil from digging out, this could get VERY expensive. The wall itself will have to go down into the ground very substantially, with a very large concrete foot.
Breaking it down into a series of terraces reduces the scale of these problems dramatically. Unless you really NEED the whole area level, I suggest you’d be better off employing a good garden designer. Well designed terraced gardens can be stunning - in general the elevations add interest and allow the creation of “zones” within the garden.
Depending on what you can do with the spoil from digging out, this could get VERY expensive. The wall itself will have to go down into the ground very substantially, with a very large concrete foot.
Breaking it down into a series of terraces reduces the scale of these problems dramatically. Unless you really NEED the whole area level, I suggest you’d be better off employing a good garden designer. Well designed terraced gardens can be stunning - in general the elevations add interest and allow the creation of “zones” within the garden.
Beartato said:
Hello all, I'm hoping someone here knows about this sort of stuff. A preemptive TDLR is that I'm in the early stages of mulling over thinking about getting a retaining wall built which would be approx 5 metres high by around 15 metres wide.
Around half of my back garden is a fairly steep slope which is essentially unusable and I fancy at some point putting a whacking great retaining wall at the end and levelling the garden. Due to the slope of the land the back garden is around one metre lower than the front as well, with a retaining wall separating them. The house is all at the front garden level, so I also want to raise this to make them match, or almost match at least.
From a very quick google it looks like a reinforced retaining wall would be the way to go rather than a poured concrete one. Does anyone who knows such things have any other thoughts. Also, I expect the costs to be eyewatering but what do we reckon a ballpark figure might be (excluding the infill material, I can get that for free.)
P.S. This is my first time on PH in about 15 years, I used to be such a lurker. Delighted to see the formatting stuff is all the same, now I'm going to go have a wander around and see if any familiar names are still around to give me a whack of nostalgia and then look for an update on the nazi garden bunker on Jersey.
Difficult to estimate cost without more detail but it will be a serious chunk of change.Around half of my back garden is a fairly steep slope which is essentially unusable and I fancy at some point putting a whacking great retaining wall at the end and levelling the garden. Due to the slope of the land the back garden is around one metre lower than the front as well, with a retaining wall separating them. The house is all at the front garden level, so I also want to raise this to make them match, or almost match at least.
From a very quick google it looks like a reinforced retaining wall would be the way to go rather than a poured concrete one. Does anyone who knows such things have any other thoughts. Also, I expect the costs to be eyewatering but what do we reckon a ballpark figure might be (excluding the infill material, I can get that for free.)
P.S. This is my first time on PH in about 15 years, I used to be such a lurker. Delighted to see the formatting stuff is all the same, now I'm going to go have a wander around and see if any familiar names are still around to give me a whack of nostalgia and then look for an update on the nazi garden bunker on Jersey.
Couple of points you may/may not have considered:
Who owns the land behind your garden? Construction of a retaining wall usually requires that the earth behind the proposed structure has to be removed / graded back to a slope to prevent collapse during the works, then backfilled after the wall is built.
At a wall height of 5m, you'd be looking at excavating spoil at least 10m into the land behind.
You may be able to avoid this by using sheet piles, but that would be truly eye-watering.
Drainage - assuming you have no issues at present & rainfall is naturally managed by the slope of the land, putting a massive wall in the way will change this.
A structural engineer is best placed to advise, but with a 15m wide x 5m high structure you will have to include a number of openings though the retaining wall at various levels to allow for flow of water.
As you have removed the soil on the "house side" that previously attenuated the water, likely you'll need to put a large soakaway system in place to prevent flooding which is further outlay.
Hope some some food for thought; think one of the posters above was spot on with the suggestion of a tiered layout. Significantly less expense with the bonus that you don't have to look at a 16ft high wall.
In your shoes, I'd spend a few quid consulting a decent landscape designer for ideas - a tiered garden across several levels has the opportunity to be an amazing outdoor space in a way that a flat plane of land can't match.
For my ignorance, does the ground slope away from you or are you looking at the slope? (I have read it twice but not 100% sure)
You mention 'which slopes 100m down to the sea', hence the question.
If it slopes down/away, then it wouldn't need a retaining wall, just a wall with a void underneath (...or a secret bunker), you could then beam & block over the void and lay the 'garden' (astro turf... --> council thread
)
It could be slabbed/decked/planters or drainage holes could be drilled through the slab and then weep holes/ventilation on the wall faces below, of you wanted a turfed garden?
However if it does slope up...I have used Crib Lock in the past and their concrete ones will do ~5m height. Equally, that could work if the ground slopes away from you.
I have just built an extension on a hill... so from the front it is single storey, but two at the back. Immediately at the back of the house it was ~1200mm lower than the front of the house prior to building. No retaining walls were built and there is a lovely services void (3m wide) to run drainage, electric, etc. through as the extension had to be far enough away from the existing to allow traditional foundations to be laid for the new work, then a new floor linking the two parts together.
As a 'raised deck' you would need planning permission, however as a PD larger home extension you could go out 8m (on a detached house) no greater than 4m high (height taken from highest point)... then stop once you have the slab in... so, worthwhile keeping that 'argument' in mind if you go via the planning application route.
You mention 'which slopes 100m down to the sea', hence the question.
If it slopes down/away, then it wouldn't need a retaining wall, just a wall with a void underneath (...or a secret bunker), you could then beam & block over the void and lay the 'garden' (astro turf... --> council thread
) It could be slabbed/decked/planters or drainage holes could be drilled through the slab and then weep holes/ventilation on the wall faces below, of you wanted a turfed garden?
However if it does slope up...I have used Crib Lock in the past and their concrete ones will do ~5m height. Equally, that could work if the ground slopes away from you.
I have just built an extension on a hill... so from the front it is single storey, but two at the back. Immediately at the back of the house it was ~1200mm lower than the front of the house prior to building. No retaining walls were built and there is a lovely services void (3m wide) to run drainage, electric, etc. through as the extension had to be far enough away from the existing to allow traditional foundations to be laid for the new work, then a new floor linking the two parts together.
As a 'raised deck' you would need planning permission, however as a PD larger home extension you could go out 8m (on a detached house) no greater than 4m high (height taken from highest point)... then stop once you have the slab in... so, worthwhile keeping that 'argument' in mind if you go via the planning application route.
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