Retaining walls?

[Russell]

Where can I get info on how to do retaining walls?
People keep asking me about them, up to 3 foot high.
I know people use sleepers slotted in I beams but how deep to go with the steel?
gabion baskets what do they sit on?
concrete Lego's, what do they sit on and what size digger will move them?

 

[Smiffy]

Where can I get info on how to do retaining walls?
People keep asking me about them, up to 3 foot high.
I know people use sleepers slotted in I beams but how deep to go with the steel?
gabion baskets what do they sit on?
concrete Lego's, what do they sit on and what size digger will move them?

Dozens of textbooks available or there are a couple of 2 day courses I looked at from various colleges and universities

 

[Gunners]

There's no hard and fast rule with these really.
Up to 3ft isn't too risky unless its holding back a driveway or inside the good old 45 degree rule of thumb from the house. Over 3ft high and for me its engineer time EVERY time. Plenty of customers don't want to pay the money for an engineer design - well they aren't the people you want to be working for!
Don't underestimate the part drainage plays in retaining walls - plenty get pushed over by water more than the dirt behind them - always allow for some drainage.
For small walls like you are talking about, a general rule of 50/50 will see you right. however high the wall is, that's how much steel or sleeper needs to be in the ground.
Precast concrete L sections or lego blocks can work well, but need a minimum of a 5t machine to handle them really.
I've also done crib walls, blockwork, hollow blocks, shuttered concrete etc but they have always had an engineer design them.
We are contractors - not designers. If you are ever unsure, get it designed. If the customer thinks you're crazy - you aren't. Its your risk otherwise at the end of the day and generally our gut feeling doesn't lie. I've walked away from quite a few who even after the design has come back and I've priced it still want me to do something cheaper! No chance mate find another idiot... which they often do

 

[doobin]

No engineer will spec a sleeper wall, all they are interested in is things like concrete that they can lookup in their tables and then add 50% extra to to cover their areas- cause they ain’t paying for it!

it’s not rocket science. Use common sense. You see dozens of softwood sleeper walls five sleepers high that are just screwed to a softwood sleeper behind. These guys keep me in business- all you need to do is be better than them.

There's no hard and fast rule with these really.
Up to 3ft isn't too risky unless its holding back a driveway or inside the good old 45 degree rule of thumb from the house. Over 3ft high and for me its engineer time EVERY time. Plenty of customers don't want to pay the money for an engineer design - well they aren't the people you want to be working for!
Don't underestimate the part drainage plays in retaining walls - plenty get pushed over by water more than the dirt behind them - always allow for some drainage.
For small walls like you are talking about, a general rule of 50/50 will see you right. however high the wall is, that's how much steel or sleeper needs to be in the ground.
Precast concrete L sections or lego blocks can work well, but need a minimum of a 5t machine to handle them really.
I've also done crib walls, blockwork, hollow blocks, shuttered concrete etc but they have always had an engineer design them.
We are contractors - not designers. If you are ever unsure, get it designed. If the customer thinks you're crazy - you aren't. Its your risk otherwise at the end of the day and generally our gut feeling doesn't lie. I've walked away from quite a few who even after the design has come back and I've priced it still want me to do something cheaper! No chance mate find another idiot... which they often do

 

[GazCro]

As @Gunners says drainage is the key it's always the extra weight/push of water behind which will push a wall over. A lot depends on what finish people want. Gabions are very good for drainage but a lot more labour intensive than you would think if you want to do a proper job of them. Lego blocks sound great but there's the weight of them to move and they are not cheap. Sleepers or blockwork are bad to beat for adaptability imho, corners changes in ground level height steps etc.

 

[Gunners]

You are right @doobin, no engineer would spec a sleeper wall. You cant guarantee the lifespan of them for starters. But I also wouldn't do a sleeper retaining wall over 3ft! The ones in your pictures look very tidy, and are a great solution for that kind of situation. But if it was the other way around and it was the drive being retained or the path next to the house - identical height - would you use sleepers in that situation or even be happy taking the liability of your own design?
Personally I wouldn't which I why I tried to give a balanced view in my post to Russel. The setting the wall is in is as important as to the height to be retained in my opinion.

 

[doobin]

You are right @doobin, no engineer would spec a sleeper wall. You cant guarantee the lifespan of them for starters. But I also wouldn't do a sleeper retaining wall over 3ft! The ones in your pictures look very tidy, and are a great solution for that kind of situation. But if it was the other way around and it was the drive being retained or the path next to the house - identical height - would you use sleepers in that situation or even be happy taking the liability of your own design?
Personally I wouldn't which I why I tried to give a balanced view in my post to Russel. The setting the wall is in is as important as to the height to be retained in my opinion.

Fair point but three feet high is barely a retaining wall!

 

[hiluxman]

Fair point but three feet high is barely a retaining wall!

I'm sure our lovely regulations say the 600mm or more is classed as a retaining wall.

 

[GazCro]

I'm sure our lovely regulations say the 600mm or more is classed as a retaining wall.

Depends whether it adjoins a building. If its a "garden wall" it isn't building controls concern.

 

[hiluxman]

Depends whether it adjoins a building. If its a "garden wall" it isn't building controls concern.

Possibly not from bc but I'm sure anything over 600mm has to have some structural value/design.

 

[GazCro]

Possibly not from bc but I'm sure anything over 600mm has to have some structural value/design.

Be one of them ok until something goes wrong.

 

[DaveDCB]

Problem you get is when someone bolts a 6ft fence ontop of your 3ft wall and after a high wind everything blows over.. granted common sense says it’s not your problem, but I’d just rather not the hassle and have someone else’s plan to follow, thus liability lays with them!

 

[DaveDCB]

Also doesn’t anything over 3ft require a handrail….

 

[GazCro]

Also doesn’t anything over 3ft require a handrail….

600mm drop max

 

[Gunners]

Fair point but three feet high is barely a retaining wall!

Maybe to you and I, but you've got to start somewhere and the principles are the same on the small ones as they are the big ones!
I attach a selection of walls I have done in the past at various build stages for discussion/ general piss taking. Some bigger than others, but all seemingly different designs. Just goes to show there isn't a one size fits all solution to these things.
Not a slab on edge to be seen!

 

[doobin]

Have you got a rebar tying machine? Best thing since sliced bread!

 

[Gunners]

Have you got a rebar tying machine? Best thing since sliced bread!

I didn't realise a zip tie machine existed. Sounds handy, does it cut them off once they are tight too? You'll have to show me when we meet up

 

[hiluxman]

I didn't realise a zip tie machine existed. Sounds handy, does it cut them off once they are tight too? You'll have to show me when we meet up

We did a slab this morning and that was a cable tie job.

 

[doobin]

I didn't realise a zip tie machine existed. Sounds handy, does it cut them off once they are tight too? You'll have to show me when we meet up

No, it ties them with wire. Didn’t think zip ties on rebar was up to spec?

 

[V8Druid]

Also doesn’t anything over 3ft require a handrail….

over 450mm