Can this lot cut and fill without having retaining walls

We have a land with some fall over across the lot. Already there are three retaining walls around the lot, done by the land developer. We had thought we don't need any additional retaining walls. After the contour survey our builder suggested a cut and fill in a way that it requires two retaining walls on both sides of the lot. On the low side the existing retaining wall is not tall enough if we fill. It's just on the current land level. That's why the builder suggest one on the high side and another one on the low side.

Following images show the contour lines in disclosure plan and contour survey plan. I am wondering if it is possible to cut and fill in a way that it doesn't require retaining walls? At least not in both sides...

 

When a house takes up a lot of room on a block it does exacerbate even small differences but with only 300mm side to side and 700mm front to back I would have thought there were other options

Things to consider/options
- 2 smaller retaining walls on each side can often be cheaper than one larger retaining wall on one side
- dropping the level of the garage to ground level (ie 97.9) and having an internal step of 2 might mean not needing retaining on the low side. Again this might be more expensive than the proposed solution
- putting the whole slab at 97.9 and cutting into the high side and retaining on that side may also be an option

 

Thanks @WestMinister!

I heard that there were some issues with other lands and some owners have managed to get the land developer to fix it. But we needs to find that they have done something not to the standard. Is this kind of land development is acceptable? Unfortunately the council seems to have approved those existing retaining walls. It's pretty bad that we have to do retaining walls just after they finished those 3 existing retaining walls, it should have been leveled at the first place.

If disclosure plan is different to the contour survey, then I can ask the developer to fix it. But looks like there is no much difference in the disclosure plan and contour survey?

Your 3rd option sounds better than the proposed option. What do you think about making the slab at 98.1? So there is only little difference and probably a bit larger garden bed will be able hold it?

 

If this was a 2 storey design then there would probably be no issue. I don't believe the block is under retained but is not ideal for your design or requirements. Your disclosure clearly stated a height difference - if there is a significant difference to what was built then yes perhaps you could ask for them to remedy but the won't make it flat.

Your garage is hard up against the boundary so you either do it at the level of the current retaining 97.9 or you put more retaining on that side if you want it at 98.1

 

If there's negligible difference between the disclosure plan and contour survey then not much you can force the developer to do..

 

In the second diagram "Pad RL = 97.825" and "Pad FFL = 98.06". Does RL = 97.825 meaning it's already been proposed to build to the lower side retaining wall height? Is this similar to the option 3 that @westminister mentioned?

 

Having two retaining wall reduces the frontage of the lot by at least 400mm. Because we have to leave 200mm per retaining wall. So, I would like to choose an option with one retaining wall rather than having two. I am not sure if that's possible though...

 

If you wanted a flat block....why did you buy this ?

I cannot see how you could entertain no retainig wall, if there is already one....I see developers buying sloped land then putting retaining walls and filling....they prob have jobs where they have excess fill to get rid of.

 

The issue is that we are not allowed to touch the existing retaining walls. We have to build another one 200mm away from the existing one. If I could raise the existing one, that wouldn't have been a big issue.

 

Then your really going to have to work with the builder and see what they can do once you say cost is not a problem, just quote for whatever options they suggest.

 

The council will also need to be liased with......

You cant change much prob as what you do effects what the others wete expecting they bought.

 

Already asked about having a stepped slab, but our builder is not doing stepped slabs. So the other option is cut and NO fill. So we need only one retaining wall. Land developer said they would take the excess soil free of charge. Not sure if that's a good idea, haven't talk to the builder about this yet.

 

Are you sure the house design you have chosen to build is suitable to that block of land?
Marg

 

as @Marg4000 and I have said maybe a different design would create less issues or find a builder who will do a stepped slab - or even a slab with downturned edge to hold the slab in place rather than retaining.

Is this for an IP or PPOR? If it's IP just change design and/or builder.

 

This is a PPOR and we actually like the house plan and the builder so far.

 

After discussing more about this matter with the builder and the retaining wall builder, looks like there is no way to avoid retaining walls. The best option we found so far is cutting the lot to PAD RL 97.6. So we don't need a retaining wall on the RHS and the backyard landscaping would be much better without a noticeable slop.

In that way, we will need a 800mm tall retaining wall on the LHS and it has to be an engineer designed one.

 

I'm glad you've found a solution and you're right that will reduce the slope at the back too = win win

 

Another issue, the developer has put something like this on the lot. It's a storm water drain but not an easement. Is it legal to do something like this when it is not in the disclosure plan?

According to the QLD government site, in the disclosure plan the developer must include "planned earthworks during the development" details which includes drainage channels (by the definition of earthworks).

Hope to contact a solicitor tomorrow, just wondering if anyone has any idea?