Retaining wall options

[eandg]

I have 1600mm to retain across my boundary. Looking at two potential options: concrete lego blocks like these or one of the  or one of the pre-cast interlinked blocks that's filled with concrete or aggregate like Stepoc.

 

I'm struggling to find much info on the founds required for either. Can anyone advise on the width and depth of footings likely required, and the depth of wall likely required below ground? I've a structural engineer but he's not responsive enough to look at the options and find me a solution so I need to find the best one to him for him to run the calcs and give me the design. 

 

Thanks

[Declan52]

I built a retaining wall to hold back my driveway using this.

https://ag.uk.com/professionals/products/walling/anchor-diamond/

 

Can be built with no concrete foundations, compacted hardcore is suitable. It's easily doable DIY as the blocks have a lip on the back so you just set them ontop of each other and pull forward until the lip hits the block beneath. Just use an adhesive like stixall to hold the top coping in place.

[eandg]

9 minutes ago, Declan52 said:

I built a retaining wall to hold back my driveway using this.

https://ag.uk.com/professionals/products/walling/anchor-diamond/

 

Can be built with no concrete foundations, compacted hardcore is suitable. It's easily doable DIY as the blocks have a lip on the back so you just set them ontop of each other and pull forward until the lip hits the block beneath. Just use an adhesive like stixall to hold the top coping in place.

Thanks - I had seen your threads previously and was thinking of that and will give them a shout tomorrow for costs. Do you know if there's a rule of thumb for how far below ground you need to go? 

[Temp]

37 minutes ago, eandg said:

Looking at two potential options: concrete lego blocks like these or one of the  or one of the pre-cast interlinked blocks that's filled with concrete or aggregate like Stepoc.

 

Those big blocks would need good access for something like a forklift, telehandler or crane with forklift hooks. 

 

+1 to what @Declan52 used. Ask if they have a design guide or design service. Perhaps not but worth asking.  

[Gus Potter]

Hello eandg.

 

Generally a 1600m retaining wall offers up a lot of options, provided the wall is not "structural"... say holding back soil that is offering restraint to your neighbours house foundations.

 

I would start with the fun part!

 

Could we use gabion baskets say and grow things out of them. Could we use gabions with cheep infill and face it up with some dry stone dyke with inset bench seating to compliment any outside seating area. What you do here is to create butresses and put seating in between.

 

What about a timber crib wall, you need a bit of space behind them to install but a well constructed crib wall will last for many years and is accepted by say the NHBC as a solution. Again you can grow things out of them and almost create a water fall effect of foliage that gives colour all year round.

 

There are many different types of retaining wall. For a lowish wall such as this a gravity wall is often a good option if you have some space. In this case a starting point for the base width would be about ~1.2m if you have a reasonably stiff clay and good drainage. The footings are taken down to the level where the soil does not contain any matter that will decompose, below the top soil. You'll still get some minor settlement but these walls cope fine with these conditions.

 

What about posting more info on your site and the type of ground you have.. you'll get loads of ideas here on BH.

 

 

 

 

Edited January 12, 2022 by Gus Potter
to add a bit

[eandg]

15 minutes ago, Gus Potter said:

Hello eandg.

 

Generally a 1600m retaining wall offers up a lot of options, provided the wall is not "structural"... say holding back soil that is offering restraint to your neighbours house foundations.

 

I would start with the fun part!

 

Could we use gabion baskets say and grow things out of them. Could we use gabions with cheep infill and face it up with some dry stone dyke with inset bench seating to compliment any outside seating area.

 

What about a timber crib wall, you need a bit of space behind them to install but a well constructed crib wall will last for many years and is accepted by say the NHBC as a solution. Again you can grow things out of them and almost create a water fall effect of foliage that give colour all year round.

 

There are many different types of retaining wall. For a lowish wall such as this a gravity wall is often a good option if you have some space. In this case a starting point for the base width would be about ~1.2m if you have a reasonably stiff clay and good drainage. The footings are taken down to the level where the soil does not contain any matter that will decompose, below the top soil. You'll still get some minor settlement but these walls cope fine with these conditions.

 

What about posting more info on your site and the type of ground you have.. you'll get loads of ideas here on BH.

 

 

 

 

 

Thanks Gus. The wall will be faced onto my neighbour (I'm higher) so largely looking for the cheapest option that he can face as he likes, though there's a bit of come and go on it. My house 1200mm from boundary. Can't go more than 250mm onto his side to allow for access so a narrower option preferred but if it's too expensive I'm happy to go with something bulkier and dig out more at my end. 25m long, 1600mm height - so 40m2 plus whatever is required beneath ground. Ground largely fine - has been dug out for months and doesn't look like it's going anywhere so largely just a boundary wall to be backfilled and drained as appropriate. 

Edited January 12, 2022 by eandg

[Gus Potter]

Hi eandg.

 

I'm guessing here as you have posted no plans or other info.

 

Being higher if a different animal. I'm guessing but if you have 1.2m from the boundary then it's good to have a levelish portion for you to clean the gutters, walk round etc. have a look on the net at what is a called a reinforced masonry retaining wall. There are lot's of different options other than a gravity retaining wall.

 

On the soft side this type of reinforced wall can be faced with facing brick on you neighbours side.. yes I know it may cost a bit more but in the long run you may want to be friends with your neighbours or find you need their good will if you need to later access their land for some reason. When  / if you come to sell you maybe want to be able to say.. we have great friendly neighbours.

 

I've do the odd job where you actually dig out a lot of the soil and replace this with ICF type blocks. What you do here is to reduce the sideways load on the wall (lateral earth pressure) as the ICF blocks are stable and much less dense than the clay.. Sounds bizarre but this can be a cost effective solution when looking at things in the round. You do have to watch the water table as ICF blocks float so you need to make sure you put enough ballast load over the top to avoid .. embarrasement.

 

Post some sketches.. plan view and cross sections if you can / have the will, sit back and let BH members take the strain.

 

 

[eandg]

Thanks again, will try and sketch something up.

[Declan52]

10 hours ago, eandg said:

Thanks - I had seen your threads previously and was thinking of that and will give them a shout tomorrow for costs. Do you know if there's a rule of thumb for how far below ground you need to go? 

They don't need to be buried like a trad retaining wall. Only need to go deep enough so you don't see the actual compacted hardcore or concrete.

The wall is built leaning back wards as the lip on the back of the block means it can't be plumb so each block steps back an inch at a time. So maybe the wall is sitting at 10_15 degrees of the plumb. 

They are fairly large heavy blocks so not going to move once they are in and backfilled with clean stones and if you use geo grid to hold the layers in place.

Another option is too use a smaller block and have 2 walls. I did this with my front garden 

1 wall about 500mm high then some garden covered in decorative stone then another wall at 1m holding back a bank and path/road. 

As the wall is a finished product you don't ever need to worry about plastering it or painting it.

[vfrdave]

I am in the process of building one at the moment using Allanblock from Colinwell a local supplier.

 

Attached is the guidance for their wall products.

ab-residential-retaining-walls.pdf ABCommManual.pdf

[eandg]

17 minutes ago, vfrdave said:

I am in the process of building one at the moment using Allanblock from Colinwell a local supplier.

 

Attached is the guidance for their wall products.

ab-residential-retaining-walls.pdf 9.1 MB · 0 downloads ABCommManual.pdf 9.41 MB · 0 downloads

Thanks (and thanks Declan), do you mind sharing rough m2 costs for the wall?

[Declan52]

I built mine in 2014 so costs would have been nothing compared to what they are charging now. It should still be cheaper than a trad retaining wall as it's DIY, don't need massive width of concrete or any steel and it's a finished face so no extra costs with render or a brick face.

[redtop]

We did one with gabion baskets. Very easy to do, but time consuming. We filled ours with quarry waste, we managed to get enough decent stone from the bags to do the facing and the rest went in the middle/ back. Worked out very cheap at 20quid a tonne. 1 bag did about 1 basket (1 cubic metre). Ish as we also threw in old blocks / bricks we found lying about. Got the angle wrong on the back row so they are leaning back more than 15 degrees, but at least its wrong in the right way ?

[vfrdave]

9 hours ago, eandg said:

Thanks (and thanks Declan), do you mind sharing rough m2 costs for the wall?

@eandg Works out at unit price of £5 +vat per block (0.45 X 0.2m). Capping stones a similar price.  This was summer 2020, invariably will be more expensive now. 

 

Then factor in the stone for initial base, filling cores and back filling.

Edited January 13, 2022 by vfrdave

[eandg]

On 13/01/2022 at 11:56, redtop said:

We did one with gabion baskets. Very easy to do, but time consuming. We filled ours with quarry waste, we managed to get enough decent stone from the bags to do the facing and the rest went in the middle/ back. Worked out very cheap at 20quid a tonne. 1 bag did about 1 basket (1 cubic metre). Ish as we also threw in old blocks / bricks we found lying about. Got the angle wrong on the back row so they are leaning back more than 15 degrees, but at least its wrong in the right way ?

 

Quick google and I'm only finding dust available as quarry waste. Gabion stone looking at £120+ per bulk bag. Any advice appreciated - have half-committed to DIYing gabions for separate bits of retention but it's looking more expensive than I'd thought!

[eandg]

On 13/01/2022 at 13:32, vfrdave said:

@eandg Works out at unit price of £5 +vat per block (0.45 X 0.2m). Capping stones a similar price.  This was summer 2020, invariably will be more expensive now. 

 

Then factor in the stone for initial base, filling cores and back filling.

Appreciated, thanks - so approx £60m2 plus the rest?

[saveasteading]

28 minutes ago, eandg said:

Gabion stone looking at £120+ per bulk bag.

You only need pretty stones for the face of it and can fill the rest with much cheaper material. Even new concrete blocks will be cheaper than that, and you can use damaged or demo material, which you may find free to collect of sites.

Depending on where you live, quarry products may have different terms, Waste is whatever doesn't have  a name and they cant sell as a product.

Scalpings for example is a mix of poor stone and clay, just as it comes. Best explain to the quarry (or haulage company) and see what they suggest.

Crushed demo concrete may be cheaper but is sometimes in demand for its greener credentials.

[eandg]

56 minutes ago, saveasteading said:

You only need pretty stones for the face of it and can fill the rest with much cheaper material. Even new concrete blocks will be cheaper than that, and you can use damaged or demo material, which you may find free to collect of sites.

Depending on where you live, quarry products may have different terms, Waste is whatever doesn't have  a name and they cant sell as a product.

Scalpings for example is a mix of poor stone and clay, just as it comes. Best explain to the quarry (or haulage company) and see what they suggest.

Crushed demo concrete may be cheaper but is sometimes in demand for its greener credentials.

Thanks - appreciated.