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I’m looking to build a 600mm garden wall to keep a raised garden bed beck back off the side of the house (previous owners though buried weatherboards was a good idea…) I initially had questions about the wall itself, but in thinking it over last night I also have some concerns about the exposed foundations.
Wall will be L shaped, 3m X 1.8m. I also had to dig out 2 trees that were in the bed and too close to the house. I've dug the trench but in doing so to get all the roots out I went about 100mm deeper, thinking it would be good to get more organics away. However I now have 2 concerns.
- 1. the trench actually goes lower than the concrete footing of the patio brick wall (about 15cm) and on the other end a small 3-4 course garden edge wall (under the footing by more than like 20-25cm), and
- 2. I have exposed the concrete around the corner stump for the house. I haven't tried to dig under it or anything and I assume/hope it goes much deeper than 30cm.
I'm not sure if either of these will create 'load' on the wall, or if they might now settle because I've dug away some of the dirt that was next to them. My plan was to fill in about 10cm of dirt (fairly sandy), compact with a plate compacter, then put in 10cm of road base, compact that, then put in the concrete footing, remove the form work and fill the gap around where the form was with the either dirt or left over roadbase.
I then plan to build the wall (questions on that below) and fill on the house side with dirt up to the ground level of the underhouse. (considered doing about 10cm of blue metal on the 'house side' but actually think dirt is better since it'll encourage water to spread rather than creating an area for it to pool by the footing. Garden side I was going to put some blue metal to encourage drainage but no actual agpipe or anything since it should drain fairly freely out the bottom of the bed?
As for the wall itself, the house is weatherboard from the 1920s and has lots of brick around other gardens and paths, so could do a 7-8course English bond brick wall on a concrete footer, on top of compacted road base. However, I'm wondering if it would be better to do something more like 2 courses of concrete retaining wall blocks (like adbri Versawall) on compacted road base (seems concrete footing is optional), then capped with a header row of bricks so the unburied part matches.
- 3. Any advice on which of brick or concrete blocks is more suitable or if it doesn't matter? It won't be very visible so aesthetics less important (I've not laid bricks before but was excited to learn)
- 4. Do I even need the roadbase? I see the other footings were just on the fairly sandy soil. I know I would have to compact it if I put it back in, and maybe now since I've dug it out the roadbase would be worth doing?
- 5. If I do a concrete footer this size (500mm wide, 3m long, then 1.7m long on the other side), does it need reo, mesh and/or contraction joints? Do I need vertical reo into the wall or can I just mortar them? The bricks I would use are solid (was planning to use reclaimed to match since not much price difference). I read conflicting things about if these are optional or required.
- 6. Should I fill in on the house side with dirt or do I need to use something else? I can hand tamp that but feels like if it needs any real support for that house stump on the corner then me tamping isn't going to do much of anything
- 7. Assuming I can build close to the existing brick walls, how do I get around the bits of concrete from the old footing that stick out? Should I cut bricks to go around that? Do I leave an air gap? Do I just fill it with a bit more mortar? Do I need to drill a reo into each end (I'd personally prefer them not connected probably, esp the patio as I don't want to compromise that wall at all and no clue how old/brittle it is.
A few photos uploaded, happy to share more if helpful. Keen to learn and try figure this out, but if you feel this is risking causing a bigger issue please shout and let me know who I should get in to take it over.
Thank you all, I've read so many helpful threads here!
Hello @matt234
I've re-assessed my proposed solution and would like to amend some of the ideas I suggested. instead of having a gap near your brick area, I recommend building right up to it, but not anchoring to the brick wall. This goes for the other side of your retaining wall. It's main purpose now is to prevent soil from going past the retaining wall.
I suggest doing some preliminary measurements, how tall will the concrete base be? how many levels of Versawall blocks will you be putting in? This should give you a better idea of the layout and quantify the products you'll be using.
For example, if the concrete base is 100mm and each Versawall block is 200mm tall you would have a total height of 500mm if you were to put two levels of the Versawall. You'll now have o determine where will the soil end up once you have part of the retaining wall up and installed.
I've drawn up some sample sketches and placed them below, please let me know if you have any questions regarding the placement of the Versawall blocks. The gap I provided for this drawing is 200mm and your concrete base is 500mm wide. These are just suggestions, and you can change their layout to suit your plans.
Eric
Here are a couple of sketches of a gabion styled retaining wall. Much like the one I posted earlier Fixing water ingress issues in garage but shorter and made with off the shelf baskets (tho you can make your own cages a lot cheaper if you wish)
This is how you have it now, you have done all the hard work! I suggest at least 50mm roadbase type gravel that is tamped down. If it levels out with the top of your foundation concrete all the better. But it will need to be compacted a bit. (I am presuming that that dotted line on your drawing is a garden edge 
)
I messed up sketching (couldnt find a pencil lol so used pen.) So new pic
So I am taking a guess and saying your retaining wall is 800mm high If its shorter then that can be accomodated as there are a few different sized baskets available off the shelf.
Jack 80 x 40 x 40cm Rectangle Landscaper's Plant Support Garden Gabion need 9 at $58.00ish ea
Jack 65 x 30 x 15cm Landscaper's Plant Support Garden Gabion $36.00ish if you are going for a retaining wall 650mm high (400mm plus 150mm baskets)
Jack 40 x 40 x 40cm Landscaper's Plant Support Garden Gabion Cube $32.00ish ea is a square corner cube if you are only having a retaing wall at 400mm high.
The lower section of the drawing is a side view of what you may see down at ground level. Most of the baskets will be below ground depending on what type and height you go for. I would suggest to make it easy for you that you keep that 400mm air gap between the wall of the house and the edge of the gabion wall. On my gabion projects I show how you can join them together if you want that. The cages would allow water to travel through, hold back the soil with a geotex cloth and last, well last for a long time
If you want more info on how to for the gabion wall just let me know. I am a fan of them
Dave
Thanks @Dave-1 and @EricL , super helpful! My wife wants the brick top so I think the Gabion might be out even though it certainly is much easier! Though this makes me think I might be wise to do the locking blocks and then just rest bricks on top for now, once happy its all stable etc I can mortar the bricks in place.
Yes @EricL, the garden bed is higher than the wall. Where you see it at the top of the trench under the grey fence is its natural level. So I would have 1 brick course higher than that so the top of the wall aligns with the bottom of the fence. The yellow string line is the wall level - from just above the patio render, to just above the plinth boards, to the base of the fence.
The trench is currently 750mm deep to build a 350-400mm wall. I was thinking 2 courses of versawall/locking bessa blocks (only 1 leaf/skin thick though not double like the revised CAD image) + red brick toppers, or 6 courses of double brick (double because people said single wasn't strong enough to retain (though 350mm isn't that tall...). This is because the wall needs to be 350mm above the underhouse 'ground' level to match the garden bed edge, then 70mm for 1st brick course buried, 150mm for the slab (perhaps overkill), 100mm for roadbase, and trying to get under the roots etc took it another ~80mm further which I plan to put back in as soil and compact before adding the road base.
Another rough drawing attached of the side view.
Morning @matt234
Thats ok, ideas are just that, ideas They dont cost anything to consider.
Think your sketch looks good, cant see any issue with it.
Dave
Hi @matt234
That is an excellent diagram of the retaining wall. Since you now have an idea of the measurements, I suggest purchasing a few red bricks and Versawall blocks to get a real time feel of how the blocks will look like when placed into position.
Please keep us updated with your progress, we look forward to seeing your retaining wall built.
Eric
Hi @matt234
I think @Dave-1's suggested solution just nails it. The carboard should be more than enough to hold the concrete in place. I was thinking of using newspaper in a large amount, but cardboard is best, and it won't add a great deal of thickness to the concrete.
If you need further assistance, please let us know.
Eric
