Dodgy retaining terraces - help with ideas on how to get a functional space

[miketheretainer]

First of all if this seems like a garbled wall of text it reflects my addled overthinking brain. So the TLDR would be any suggestions to make this a decent space? 

 

I have bought a house with a fair size but completely unusable garden. 

 

It has a total of 8 different levels of terrace, a lot of which is totally unusable because of sheer drops and narrow spaces. 

 

I have a small patio and then a 1.7m high timber crib retaining wall which, although stable at the moment is currently rotting away. This merges into a blockwork retaining wall at the right hand side (some of the blockwork is built directly onto the timber!) and holds up the first two terrace levels. 

 

About 1.8m back from this there is a further 1.3m elevation to the first of a hodgepodge of levels that vary in height from 0.28 - 0.38m. Then there is the final blockwork wall at the back, some soil and then the boundary wall which is owned by the church we back onto. 

 

The quality of the current structures is giving me a real concern, the wall at the very back (with the lions face) the footings don't extend to below the flagstones, the wall is cracking at the right hand side and is just overall very poor quality. 

 

I have been constantly racking my brain as to the best way to go about this, I would and will hire a structural engineer but I can't tell him what I want. 

 

The first idea I had was to increase the height of the first retaining wall to the rear of the timber crib, and then backfill this in so that the whole top level is one level, I've given this up as a bad idea though because the of the quality of the existing blockwork. 

 

Second idea would be to dig out everything after the first level. and take it as far back to the boundary wall as possible before building another retaining wall to shore up the church wall. I have no idea how much this is going to cost, how to stage the works etc. Next door on the left has got a concrete slab base a bit higher than my garden, so probably need to retain this as well. Next door on the right their garden is well below the level of mine so not much needed on that side. 

 

I have attached pictures. The blue highlighted section is the one I am thinking about digging out. 

Edited April 9 by miketheretainer

[Mr Punter]

I think it would be worth getting a topo survey done so you can see what you have got.  You can then work out what you would like (bin store, clothes drying, bbq , seating etc) and plan the space and areas and how they will connect.  Is this a DIY project?

[SteamyTea]

Many years ago I stumbled upon Barnsdale Gardens, it is where Geoff Hamilton had his TV studio set for Gardener's World.  What amazed me was how small each set was, and how different they where.  Should be possible to combine a few.

Well worth a visit if you want to go Rutland way.

 

Failing that, get a book for inspiration.

 

[Jilly]

A terraced garden can be very interesting and attractive. 

[Gus Potter]

9 hours ago, miketheretainer said:

First of all if this seems like a garbled wall of text it reflects my addled overthinking brain.

Good for you as you are thinking about things.

 

I note you provide no details on the boundary wall and what is behind that! a Church? .. but no other info.. levels etc.

 

This is the key.. you can't destabalise your Neighbours house or garden.

 

If you can let us see what is over your boundary in a bit more detail.. just get it out now in the first wash.. Yes you see a terraced garden.. I see stepped / battered ground that the previous owner has planted up, and probably messed about with.. look at the crib wall!  maybe already dug away ground that leads me to think that it (the stepped ground) was there for a reason. You have a timber crib wall.. date that and you'll probably see that previous owners have already pushed the boundaries a bit. 

 

I think you know deep down that if you want to level things up it will cost a lot..

9 hours ago, miketheretainer said:

before building another retaining wall to shore up the church wall.

I think you need to draw some cross sections that also show the ground on the other side of the boundary and where the other structures are,  put some dimensions to all of this before anyone on BH can give some meaningfull input. Sometimes I look at a set of photos and think.. what is not included!

 

if you want some advice then provide this information and enough detail so folk on BH can chip in with good site specific advice as opposed to try to second guess what you are thinking and what lies on the other side of your boundary wall.

 

 

 

[miketheretainer]

Thanks for everyones input so far.

 

In terms of the design spec of the garden it is very much: as much flat space as possible. I have a 2 year old and just want a safe space for her and somewhere to sit out. 

 

I have drawn some cross sections of the measurements to help with what Im trying to describe. Ive split it into 3 sections with a further cross section 'Face on' as well. 

 

 

The neighbours to the right, the ground level is lower than mine so dont really need to worry about that. 

 

I've been speaking informally to a structural engineer who has been giving me some pre design advice about the back wall specifically. I think im going to have to dig a few test holes to find the footings of the church wall to see the furthest point back in my garden I can retain if I want to dig out, I now understand i will only be able to excavate above a 45 degree angle from the base of the footing. This will give me the maximum space I can gain on the level above the timber crib wall (which I am going to dig out and renew with whatever is the most economical once I've decided on a plan.)

 

The engineer also gave me an option to consider of underpinning the church wall, digging down under the wall in staggered 1m sections and then filling with concrete and doing this in stages until the wall is fully underpinned by concrete. 

 

Either of these options will mean liasing with the church under the party wall act with the latter probably being a lot less likely to be accepted. 

 

The third option is building a single 2nd retaining wall higher on the right hand section, and then backfilling it with the excavated soil from the left hand section, giving me a larger level ground 3rd level and not having to do anything that undermines the churches wall. The issue im having with this is, will the extra weight on the higher level affect the design of the smaller ground level retaining wall (currently timber crib) on the right hand side? How far back will this 2nd retaining wall need to be from the current timber crib face. 

 

hopefully that makes it a bit clearer the types of things im grabbling with. 

 

Initial budget for this work available to me right now is £10k. Don't know how far its going to get me!

[miketheretainer]

So been speaking more to an engineer and the plan is to get a 3 meter wall installed on the front of the lot and then backfill everything behind it until its level. 

 

£1k for the design of the wall, £450 for  pre design information gathering, costing/ordering the materials etc and some project management.

 

Engineer has suggested getting an architect to do the drawings for the planning permission which I'm looking at pricing atm, because he says it will speed things up/they should have a relationship with the LA etc. 

 

Anyone got any experience with planning permission & building control for a similar project? Any tips?

 

Then the big unknown is just the cost of the wall itself. 3m high by 12m long geogrid reinforced concrete block retaining wall. Your guess is as good as mine. Clueless how much its going to be.

 

Going to have to pay to find out I guess!

 

 

 

 

[Gone West]

11 hours ago, miketheretainer said:

Then the big unknown is just the cost of the wall itself. 3m high by 12m long geogrid reinforced concrete block retaining wall. Your guess is as good as mine. Clueless how much its going to be.

Here's a couple of ideas to start you off.

 

https://retainingwallsolutions.co.uk/case-studies/gabion-basket-retaining-wall/

 

https://retainingwallsolutions.co.uk/interlocking-block-retaining-wall/

 

 

[PNAmble]

We had to build a 3m retaining wall and the cheapest at the time solution (last year) was gabions. The cost was part of the ground works so don’t know the exact price but there are web sites to quote.  I’ve attached the structural engineer design

 

however. It’s not easy to find someone who is good at filling them, and getting stone to the location could be an issue.