Need help with retaining wall specifications please

[Alancove]

I am meant to be building a dry stone retaining wall in the coming weeks for a friend which is my 1st solo job. The wall length will be around 20m and Height 1.3m. It is only side that needs to be tidy as the back side is just being filled up to level. I am unsure how thick I should make the wall? What type of support does it need as in ties i.e... Am i correct in my measurement for materials needed as a formula (W)(H)(L) /27? Do i need drainage also even though it's a dry build with probably very little mix used?

Your help and advice would be greatly appreciated.

Thanking you,
Alan.

 

[r896neo]

To be honest if you don't know these details you maybe shouldn't be building it.

If it was a normal wall then go ahead of course you always have to start somewhere as a solo project, but a retaining wall that height is bordering on needing designed by a structural engineer.

 

[EB1caneyeB]

As above really.

If however you proceed i would certainly apply drainage in the shape of 40mm wast pipe, slightly recessed form the face, 100mm from the ground level, on face side, 600mm apart.
If the back of the wall isn't going to be seen i would consider backing it in 6" dense concrete blocks for retaing strength. But i know nothing of what your customer requires.

Obviously, the top course of blocks would have to finish before the ground level on the retained side. Then be topped to finish height with your dry stone wall.

I would talk it through with the customer and explain (not too deeply so as to confuse him) that this would be the better way to ensure a safe, good looking, and lasting wall.

Materials wise may be a bit of guess work if you haven't done it before. Thinking back to when i first started i used to under order and top up as i needed. It's a little hassle but you have a fair size wall to do there. You're not going to do this job in 2 days so watch how much you use of your first order and you should be able to gauge very closely how much you need to finnish the job.

How have you Priced the job if you're not sure how much material you need ? Or will you being doing job on a day rate ?

Didn't mean to write this much...soz

 

[Alancove]

Thanks for your help EB1.... I haven't priced it all as i'm living on a farm in Australia for the next few months and doing it more as a favour than for profit really. It it not a wet area and seldom rains and doesn't have too much to be supporting really so it doesn't have to be real professional as such but would just like to make it good all the same.

It's a granite like stone which ill be using and they hadn't intended using cement at all so there won't be much but just wondering should I still use the drainage you suggested? What would be an ideal way of putting a support also just in case. It is being filled behind with sand if that's of any difference?

Thanks a lot form your help guys! Much appreciated!

Alan.

 

[^woody^]

To be honest if you don't know these details you maybe shouldn't be building it.

That applies to every single trade. That is why bricklayers follow plans, and not just make the thing up themselves.

 

[^woody^]

The construction is a bit vague. If this is a random rubble wall, then its not as random as it sounds and you would need experience of how to bond it all in

I'd say that a 600mm thick wall, properly bonded would be enough, and the top 1/3 could possibly be reduced to 300mm

But if you are backing it in blockwork, then 150mm blocks would be OK with reinforcement in the bed joints every 450mm. Otherwise go for a 225mm thick block or two 100mm blocks. And then say, a 300mm or so wall in front?

Normally you would hang some steel ties out the front for the rubble wall, but I am not sure how these would bond unless you use mortar

If you are using all dry stone, then you should put a geo-textile membrane down the rear face to stop sand or dirt being washed into the wall

And don't forget the footings at least 300mm deep and 1.5 x the wall base width

 

[Alancove]

Thanks a lot for that woody. That should be enough to get it sorted I think. Cheers for the help guys. Appreciate it!

 

[theoldun]

Know nothing about dry walling in roo land. Know enough to get by in UK.
You have approx 13m3. Granite weighs in about 2.75 tonnes m3 so you will need approx 36 tonnes.
Dry stone walls should be twice the thickness at the base than the top.
In your case set the base at 700 wide and the top 400 wide Take back up vertical and the front on the batter. Set your A frame profiles at 7m centres accordingly.
We never lay concrete foundation. Dig trench 800 wide by400 deep and lay straight of sub ground.
Go through heap of stone, sort out all cope stones and set aside. Sort out through stones, about 120 number, and set aside and all large stones for bottom. Stones you are left with are your laying stones and infill rubbish.
If you are backfilling with sand, let sand filter into back joints, will strengthen wall
You should average 3 to 4m2 per day.
Good luck, believe me, you will need it and crate of amber per day.
Regards oldun

 

[r896neo]

r896neo wrote:
To be honest if you don't know these details you maybe shouldn't be building it.

Woody wrote:

That applies to every single trade. That is why bricklayers follow plans, and not just make the thing up themselves.

That is why i said it needed designed by an engineer then he would have plan to follow and not just make it up himself.

I'm probably a bit over the top about retaining walls but have seen some down-right dangerous efforts which were most likely guessed at.

 

[ABCwarrior]

I built a 2.4m radius semicircular(10m length by 1.2m high) dyke in the worst possible stone you could use- glacial rounded boulders... With no foundations, because we have no "real" soil anyway...

In the UK you don't need planning permission/engineering design until over 4ft/1.2m.

I'd advise to go for it, if the blocks are angular as granite should be, it should be easy enough, and always follow the principle that the longest tail(side) is built INTO the wall not along the face to maximise coverage, far less likely to collapse this way. If you can source any really long stones space them along it tied into the backfill that will go in. And give it a generous batter. You'd get away with 450 at the base and 350 at the top, especially if the back is freely drained.
It depends on the size of the material used, but well bonded large blocks with well placed pinnings won't be in a hurry to move. I can walk around on the coping boulders on mine and it's solid....

 

[ABCwarrior]

this ****ing site never lets you spell dike correctly...!

 

[ABCwarrior]

D*Y*K*E....

Untitled

• ABCwarrior
• 5 Apr 2012
• 2

 

[Alancove]

Thanks a lot for that ABCwarrior. A bit of reassurance for me and not much pressure to force a collapse really on mine. Once started I will upload prgress pics.

Thanks again guys

 

[EB1caneyeB]

Yeah pics. I look forward to them Alan. Close up, medium distance and further back pleeeeeze.

 

[Alancove]

Will do. Let hope it's still standing when I go take the camera out