Retaining wall - Site engineer/Site surveyor advice

I've designed a garden with a retaining wall to retain a bank which wil create a new terrace area making the garden more usable for the client. I'm planning on using a dry stone wall product by Tobermore. I need advice from a Site Engineer or similar as to what I propose to do is ok. If anyone is in the trade or knows someone id be very appreciative of some advice.

I believe what I propose to do is ok but the client has asked if the excavations will effect the house. I dont believe they will but i need some advice of and engineer before taking the project onto the next level. What I dont want to happen is the project run into alot of costs before its even started. As I may look at redesigning the garden terracing into smaller terraces using either the same walling product, standard wall construction or sleepers.

Many thanks Nic

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Permalink Reply by phil smith yewtreelandscapes.com on March 4, 2012 at 17:42

some pics of the area would be good, how far away from the house do you plan on putting the footings for the new retaining wall, what height will the wall be going and what gradient is the garden on

Permalink Reply by Nic Johnson on March 4, 2012 at 17:51


 a very simple sketch outline of the cross section intended not to scale the retaining wall needs 2m behind it for backfill with geogrid membrane in between layers and type 1 fill
Nic Johnson said:

Permalink Reply by phil smith yewtreelandscapes.com on March 4, 2012 at 18:00

if it was me doing the work i wouldnt be to concerened about a site surveyor because you will be far enough away from the main house footings, but if it was going the full length of the garden i would be more concerned about the privacey of the neighbours as the new level of the earth will be nearley as high as the fence in the background 

Permalink Reply by Nic Johnson on March 4, 2012 at 18:09

Im not too concerned about getting an engineer myself the client asked about what effects to the house insurance it would make. At first I said the same as you its far enough away but on contacting tobermore they said you should get a site engineer but to be honest i think there just covering themselves. The wall is going almost the length of the bank but not to the end nearest the fence it curves around. I may make the whole terrace  slightly lower by sloping more, the edge along the top of the wall will be planted Im not too concerned about privacy as nearly half of the new terrace will be planted

Permalink Reply by gary newton on March 4, 2012 at 19:35

i was a site agent for 20 years and i would have no concerns unless the nearest point of excavation to the house as shown on your detail was undermining the  house foundations as you are running parallel with them on a house of that nature the bottom of foundation should be around  1200 below  ground level

looking at your sketch you seem to be far enough away not to warrent any concern but you need to look at draining the wall otherwise you may have a issue behind your structure --just incorporate a french drain or similar

a structural engineer with probably cost you around £500 to prove this 

i would say you are wasting your money taking advise 

Permalink Reply by Nic Johnson on March 4, 2012 at 19:42

Thankyou very much this is excactly what I was hoping for. I was guessing it would cost me around that and I didnt want to spend that kind of money for a simple answer just for piece of mind so to speak. Im hoping to see the client again to have a look at the pictures of when the extension was built as it is fairly modern it should have deep foundations im hoping the pictures will prove this

 

Thanks again Nic

Permalink Reply by phil smith yewtreelandscapes.com on March 4, 2012 at 19:43

as i have already said i wouldnt bother, BUT if the customer insists on having an engineer come out and is prepaired to pay for it then thats up to them, just agree with them and go with their needs, more chance of getting the job then

Permalink Reply by gary newton on March 4, 2012 at 19:48

have a look on the net at gabion baskets  they are ideal for for this situation there are usually on line calculators that help with the design

Permalink Reply by Nic Johnson on March 4, 2012 at 19:55

the customer hasnt insisted on an engineer but if he does and will pay i dont mind

i've looked at gabions but there not as flexible to design curves with as the walling product would be and they dont want to look at gabions so i would need to cover them with something as well. The tobermore wall product you fill behind and use geogrid inbetween layers which binds the whole thing together and acts as a large mass. the wall can be built in curves of any type and the client loves the idea

Permalink Reply by gary newton on March 4, 2012 at 19:57

good luck hope all goes well

Permalink Reply by Nic Johnson on March 4, 2012 at 20:06

cheers

gary newton said:

good luck hope all goes well

Permalink Reply by Michael Burt on March 4, 2012 at 20:23
Hi Nic,
I was a civil/structural engineer before I started the gardening business an as Gary says you'd need to be a whole lot closer to the house before the excavation would be an issue. What you're proposing looks fine.
Regards,
Michael
Www.vialiigardendesign.co.uk

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