Can we replace the new retaining wall in front of an old one?

Forums › Home Workshop DIY › Can we replace the new retaining wall in front of an old one?

mydactylogram

4 posts

Wannabe Geek

#265390 19-Jan-2020 22:49

Hi guys

My existing retaining wall is leaning out. Property is more than 20 years old now and due to original poor workmanship, the wall start leaning out.

I got few quotes so far and couple of them suggest we replace the new retaining wall in front of the old one.

I did some research some suggest it would provide additional support and some suggest it would adding more pressure to the new walls.

I am totally lost now, any ideas what I should do?

Thanks guys.

1 | 2

465 posts

Ultimate Geek

#2401881 19-Jan-2020 22:58

Posting a picture of the retaining wall would help.

How high is the retaining wall and is it on a boundary?

Ruphus

465 posts

Ultimate Geek

#2401882 19-Jan-2020 22:59

And welcome to geekzone.

mydactylogram

4 posts

Wannabe Geek

#2401889 19-Jan-2020 23:18

Thanks Ruphus. Pic uploaded. The wall is 1.2 meters high. Appreciate your help :)

eracode

Smpl Mnmlst
8855 posts

Uber Geek

ID Verified

Trusted

Subscriber

#2401909 20-Jan-2020 06:42

Sorry I can’t comment from an engineering point of view - but if you put the new wall in front of the old, aren’t you going to move the de facto boundary (but not the legal one) quite a lot and effectively lose a lot of property area?

Although I said I can’t comment - to me the existing poles look underdone in terms of diameter and spacing - and in that case possibly also depth. If the existing wall is not in real danger of falling over, why not just give it a good clean with Wet n Forget Deck Scrub or similar - and live with it.

Don’t know where you’re based but a quick check on Auckland Council’s website indicates that retaining walls lower than 1.5 m do not need building consent - I guess other councils are likely to be same/similar.

Sometimes I just sit and think. Other times I just sit.

Bung

6484 posts

Uber Geek

Subscriber

#2401930 20-Jan-2020 07:42

eracode:
Sorry I can’t comment from an engineering point of view - but if you put the new wall in front of the old, aren’t you going to move the de facto boundary (but not the legal one) quite a lot and effectively lose a lot of property area?

Although I said I can’t comment - to me the existing poles look underdone in terms of diameter and spacing - and in that case possibly also depth. If the existing wall is not in real danger of falling over, why not just give it a good clean with Wet n Forget Deck Scrub or similar - and live with it.

Don’t know where you’re based but a quick check on Auckland Council’s website indicates that retaining walls klower than 1.5 m do not need building consent - I guess other councils are likely to be same/similar.

Need for a building permit would depend on how close the neighbouring house was. The wall could also be old enough to have been built before the Building Act relaxed the height limit to 1.5m so possibly should have had approval in first place.

What does the wall look like further along past the overloaded fence?

xpd

Geek @ Coastguard NZ
13765 posts

Uber Geek

Retired Mod

ID Verified

Trusted

Lifetime subscriber

#2401945 20-Jan-2020 08:00

You would prob need a fairly hefty wall to prevent the old one from pushing the new one out over time.

We replaced all our fencing along a retaining wall because the wall was pushing out and leaning the fence out. Next task is to remove the wall, dig it back, and replace it properly (whoever did it, had no clue what they were doing). The fence is done in such a way we can take it down easily while the wall is getting re-done, so not losing the fence :)

We wouldnt worry about it except its a driveway to the neighbors on the other side.

Gavin / xpd / FastRaccoon / Geek of Coastguard New Zealand

LinkTree

mydactylogram

4 posts

Wannabe Geek

#2402030 20-Jan-2020 10:06

I got few quotes so far. One of them who I can located on the builder register suggested they can build the new one in front of the existing one and just let the old one rot. So the boundary wiill be push forward to us about 20-30cm. Is it this the right thing to do? Couple of concerns:

1. In terms of the legal boundary and would it affect compliance and insurance perpective?

2. Will the old wall adds even more pressure to the new one?

Tradepub

Free professional, reference and technical white papers (affiliate link).

evilengineer

466 posts

Ultimate Geek

#2402187 20-Jan-2020 11:10

Couldn't your builder just install a series of new poles (properly sized, of course) in the spaces between the existing?

Which would straight away half the load on the existing poles.

The lean would be "built-in", which may be unsightly, but it would stop any further movement without the disruption of total rebuild.

Clima

130 posts

Master Geek

Lifetime subscriber

#2402195 20-Jan-2020 11:17

A few comments.

1. If a new wall is built in front of the existing it is nor retaining anything - just waiting to catch the old one as it fails.

2. The old wall is there to hold up your neighbour's ground because of excavation on your side.( Presuming that the neighbour has not filled) As such you will probably be responsible for any damage caused by ground movement.

3. The old wall will not add extra pressure to the new wall. It will just pass on the pressure it was supposed to withstand in order to hold back the earth behind.

4. It appears that the neighbour has a structure next to the wall, possibly a carport. If so, this means there is extra weight on the ground (loading) next to the fence and this probably will need council consent.

gzt

17127 posts

Uber Geek

Lifetime subscriber

#2402404 20-Jan-2020 14:32

Imo generally this is a bad idea as issues behind the old wall like inadequate drainage provision from 25 years ago will not be resolved. Ie; make a bigger mess and shorter life for the new one.

You could still build in front of it after assessing the issues, but even then most professionals would want to take it out down to ground level.

Pretty sure you need consent for this - the consent process is designed to ensure the replacement is engineered to the required standard and prevent disasters.

eracode

Smpl Mnmlst
8855 posts

Uber Geek

ID Verified

Trusted

Subscriber

#2402440 20-Jan-2020 15:41

As an example, here are the Auckland Council guidelines on retaining walls. OP’s wall is 1.2m but whether or not he needs consent depends on the surcharge issue.

Sometimes I just sit and think. Other times I just sit.

ZMF

12 posts

Geek

#2406322 24-Jan-2020 22:56

OP I would get an engineer involved and to advise. The existing retaining wall might have been added there before the neighbour added the structure next to it. Seeing that it is right next to what looks like a carport I would guess the extra weight was not considered in the design? Difficult to see in the photo, but is it not the fence that is falling over and not the retaining wall? Although I would also check the rest of the retaining wall, maybe it wasn't installed at a slight angle:

Either way I would consider installing a new one with an Engineer involved.

mydactylogram

4 posts

Wannabe Geek

#2406324 24-Jan-2020 23:04

Hey guys, thanks for all your reply above. The shed you see it is a garden shed. It’s neighbour’s garden not a carport. I was advised if we build a new retaining wall in front of the old one the boundary will move towards us by 200-300mm plus the material it will be taken almost half meter of our original boundary which definitely a no for us.

ZMF

12 posts

Geek

#2406325 24-Jan-2020 23:12

You already have a little planter there,so in that case I would build a support for the existing retaining wall and make it a planter

jim.cox

224 posts

Master Geek

#2406390 25-Jan-2020 07:19

mydactylogram: I was advised if we build a new retaining wall in front of the old one the boundary will move towards us by 200-300mm plus the material it will be taken almost half meter of our original boundary which definitely a no for us.

As a surveyor, I should chime in here...

Except in a couple of very unusual circumstances, the boundary will NOT move if you build in front of the old wall.

You will still retain ownership of the land behind the new wall and up to the boundary.

But that land may not be of much use to you.

=mjc=
.

1 | 2