extend retaining wall

Hi

I got a new land which is on a very gentle slope. Behind the back of my land is an existing house. There is already a retaining wall with fence on top in place (as the boundary between my land and the house). My land is above the existing house.

The builder Weeks said that it needs to put in new soils to raise the level for 1 metre. As a result, I will need to have a 1 metre retaining wall to be put around the boundary. I understand that the new retaining wall should sit on top of the existing ones.

I am very concerned about the cost to 1) level the land and 2) the additional cost to raise the existing retaining wall by another 1 metre.
I am also concerned if I will need to take down the existing walls and put in the new ones. In this case, the cost can be huge, I wonder.

The length of the retaining wall is about 40m.

Please helps. Any advice would appreciated.

I think you are going to require an Engineer to assess the construction.

Hi hlc
What sort of retaining wall is it, more info required also photos would help.
I wouldnt recommend putting one wall on top of the other.

it sounds like your options are

1. Replace the existing wall with a new 2m high wall
2. Excavate behind the existing wall (leaving it in place) and construct a new 2m high wall.
3. Construct a new 1m high retaining wall at least 1m from the existing wall.

Whichever way you will need an engineer.

If you want to understand a bit more you can check out this link: http://www.anewhouse.com.au/2012/05/und ... ing-walls/

Thanks a lot for all the replies. It sounds to me that any one of my options can be costly.

Is it possible to build the house on the concrete slab instead? In that case, the house will be raised by sitting it on a concrete slab. Then the surrounding of the slab will not be raised and as a result, I don't need to build a retaining wall. Not sure if this is a feasible option and whether the cost will be lower or not.

Thanks again.

Hi hlc
You need to post more info,contours, photos, sketches, etc
Some options for retaining are
1. Retain on the boundary independent of your slab
2. Retain under the walls of the house
3. A combination of 1 & 2 above

Unfortunately, the builder has the details of the contours map. I will try finding some plans.
But I have attached a sketch of the plan in my dropbox (I don't know how to upload pics here)

https://www.dropbox.com/s/hu0ny9bw6tldi ... h.jpg?dl=0

StructuralBIMGuy, thanks for your comments. Your suggestions (Retain under the walls of the house) sound interesting. Do you have some further info how this works? Thanks.