Retaining Wall Advice

[roach]

Ok folks,

Need to build a retaining wall at the bottom of my garden 5m wide by 1.8m high and would like to know if my plan is suitable.

Founds going to be dug down to solid undisturbed soil of 250mm thick concrete, 750mm wide.

7n concrete block layed flat 2 blocks deep at the base for about a third of the height and then reducing thickness to a single block on flat for the top third.

Perforated pipe layed in gravel behind wall at base for drainage.

Is this going to be sufficient?

The wall will be returned at the ends with steps on one side. What is the best way to return the footings? Do I just dig the trench at a right angle into the bank

 

[Static]

Probably wouldnt work unless your cutting into some solid rock.. base is too small and blockwork is far too light for decent retaining walls..

Gonna need more info
Whats the soil type (clay etc)?
Whats being retained behind (garden, road, railway)?
Do you plan to attach a fence to the top?

 

[roach]

Soil type is clay. Trying to tier my sloping garden so it's just a bank and going to put a wooden garden shed on top.

 

[Static]

Right.. standard garden block laid flat retaining wall, into solid clay.. maximum height of 1700mm (anything beyond that and masonry isnt really the way to go)

Your looking at something in the region of..
1100x300mm deep concrete base (central to first course of blocks)
Medium density 10.5N blocks laid flat..
The first 300mm to be 665mm wide (ie 3 blocks)
Then 600mm of 440mm wide (2 blocks)
Then last 800mm as 215mm wide
Wall should have weepholes every 1.5m or so..

 

[roach]

Loads of thanks for your detailed reply Static!!

I've just had a brainstorm though. The only reason I'm levelling this area is to put a large wooden shed/workshop on top. So what I thought of doing is to just build either a standard wall at the bottom of the bank or even just some large pillars. I could then sit the shed on top of joists negating the need for a retaining wall. What do you think of this idea? Could I just use a 4" wall with piers or would pillars be ok? Not sure about footings for the pillars though!

 

[freddiemercurystwin]

Your brainstorm aside you should be aware of the Planning Laws. http://www.planningportal.gov.uk/england/public/buildingwork/projects/workcommonoutbuildings/ I'm not sure what happens if you build the ground up first and then build your shed. If you have nosey neighbours etc you may wish to check with Planning that you are not in breach of any thing before you go ahead.

 

[roach]

Your brainstorm aside you should be aware of the Planning Laws. http://www.planningportal.gov.uk/england/public/buildingwork/projects/workcommonoutbuildings/ I'm not sure what happens if you build the ground up first and then build your shed. If you have nosey neighbours etc you may wish to check with Planning that you are not in breach of any thing before you go ahead.

Hmm does say:

"Maximum height of 2.5 metres in the case of a building, enclosure or container within two metres of a boundary of the curtilage of the dwellinghouse.
No verandas, balconies or raised platforms."

It will be within two metres of the back boundary and will be well over 2.5 metres. Can't see the neighbours having a problem as their gardens are also sloping down away from the house, and outside of the rear boundary is woodland(not sure whos woodland though).

 

[freddiemercurystwin]

My work here is done. You have been informed..............

 

[roach]

Ok thanks.

Any advice on building the block columns, foundations etc or do you think I should just go with the wall?

 

[Static]

Loads of thanks for your detailed reply Static!!

I've just had a brainstorm though. The only reason I'm levelling this area is to put a large wooden shed/workshop on top. So what I thought of doing is to just build either a standard wall at the bottom of the bank or even just some large pillars. I could then sit the shed on top of joists negating the need for a retaining wall. What do you think of this idea? Could I just use a 4" wall with piers or would pillars be ok? Not sure about footings for the pillars though!

NP.. must have been in a generous mood..

edited..

Putting the shed on stilts is always an option.. probably be alot cheaper as well..
Could go either with a free standing wall with shed on top or masonry columns with timber beam spanning between to support shed.. sure..