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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
Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thank you for sharing your question about a raised garden bed.
I suggest having a quick look at this discussion - How to lay bricks for raised flower bed? by @Brunnie_Rich. Some elements of your questions are discussed in the post.
In regards to the trench level, I suggest having the soil level all the way around. In this manner you won't have to compensate by building a concrete base that is higher on one side. I don't recommend attaching anything to your house foundation. It's best left alone so that your raised garden bed will be independent of the house foundation.
You can pretty much use any brick you prefer; The advantage of the hollow brick of course is that you can insert Reo bars for extra support. This will require precise brick laying on your part, if you decide to reinforce the wall. The holes in the brick must line up in order for the Rio to pass through.
I definitely suggest putting road base to provide a stable foundation. You'll see this discussed in the post I suggested. Putting Reo mesh into the footer is necessary as it will add strength and keep the footer stable should any breaks occur.
When you begin putting the bricks in, I suggest filling the gap at the back between your house and the garden bed when it reaches the original soil level. In reference to this, I also suggest a minimum gap of at least 100mm between your house wall and the brick garden bed. The gap between the garden bed and your wall will facilitate air flow and prevent condensation from forming.
Filling the gap between your garden bed and the house should not be an issue, ordinary soil will suffice. But I suggest tamping it to make sure that it does not settle unevenly. As to your final question, I suggest building away from the existing brick wall by at least 100mm. As I mentioned earlier, it's best not to attach anything to your house foundation and leave your raised garden bed independent.
Here are some handy guides once you've built your raised garden bed:
- How to fill a raised garden bed by @Noelle
- How to choose the right soil for your plants by @Noelle
- How to determine soil health by @Noelle
Let me call on our experienced members @Dave-1, @homeinmelbourne and @Brunnie_Rich for their recommendations.
If you have any other questions we can help with, please let us know.
Eric
Afternoon @matt234
Nice excavation I muist say 
It gives you a decent area to build easily. I havnt done any brickwork before tho gabion retaining walls yes I have.
With your brick wall I like the tamped roadbase (not worried about sand being under it) then concrete footing with reo as its a sizeable length.
I do have a question, where will the water go? Its pretty much like a dam that you are building and to me that means the water will change its course and pool elsewhere. The Fence post I can see is something I would factor in. One day you may want to replace it and if I have read right then the retaining wall is right next to the post. I do like the 100mm from the house (tho would like a larger distance) , especially to allow the timber to breath, tho as the fence post issue you will be blocking out the lower weatherboard courses from being repaired/painted type deal.
From what I can see the wall is going to be around 5 brick courses above the under house ground level? I wonder if it would be better to leave around a foot gap for maintenece issues between the house wall and new retaining wall? If its all goingto be back filled id go bessa blocks as less bricks to lay.
Last question, does the ground slope towards the house or away? If its towards the house and in particular that excavation point I would suggest to factor in drainage..
I had a water issue with araised garden area as well. In the end I excavated it all out and installed a gabion wall around 800mm from the brick wall.
Gabion Wall to stop water ingress to garage is the project if you want to have a wander through it.
I was going to do exactly what you are suggesting at first. The more I thought about it the more I did not want to have to dig up, pull up stuff to fix anything if it became an issue down the track. I decided to instead make the distance wider and use it functionally. One day I will have a door at the end and a workshop under the house. Thats the plan.
Dave
Hi @matt234
Those were excellent points raised by @Dave-1. I agree with him in regards with looking after water flow and drainage. It's important that your raised garden not block the natural flow of water as it might flood the bottom of your house.
If you need further assistance, please let us know.
Eric
Thank you both, @EricL and @Dave-1.
The question I had about the level was a bit unclear. The base of the trench is a flat single level, my concern is that this base is lower than the concrete footings I've unearthed at either end and at least partially the corner house stump. I wasn't sure if that would create issues with any of those cracking and falling away towards my trench.
The minimum I was going for between the wall and the house was going to be 100mm, but on reflection that'll make it hard to do painting etc as Dave mentioned so I might see how far out I can get it without leaving myself a tiny unusable garden bed space. (the dimensions I gave are just for the solid concrete footing, currently from there to the edge of the bed would be ~500-600mm so could probably bring it back a bit.) Will have to think about that fence post... not sure how much I can do about getting close to that.
As for the gap of 100mm between the wall and the patio wall on the right side, if I leave that gap what can I do to stop the soil etc eroding through that gap around the wall? Presumably I'll also need to just bury up to covering that footing again. I could take a few more measurements and see if I can do my footing at the same level, and then hand tamp some road base between the footings? I know I should leave 100mm between the footing edge and the side of the wall, is it the same at the end of the wall? The patio clearly hasn't done that, its maybe 20-30mm. Just thinking I could end up with quite a gap if its patio brick wall, ~30mm footer overhang, 100mm gap, 100mm footing edge space (labelled in red in the image). That's a lot of space with nothing holding back the garden bed. (if not clear, I'm just building an L shaped back wall to an existing bed that previously had no back wall and just filled from the patio to the housewall to the fence) I've uploaded a sketch (not as nice as a CAD) top down view in case it helps a bit.
Regarding drainage, the block slopes towards the right of the first image, so I'm not too worried about it pooling as water has never pooled in that garden bed before so I assume it drains out through the sandy soil pretty freely.
As for the brick type, I was looking at the versawall or something similar for 'locking' so I don't have to mortar them in, vs besser blocks which I would. It does feel like it would be a lot easier than all that brick work. Might do the footing then see how handy I'm still feeling.
Lastly, on the footing, I read somewhere that it should be 500mm wide, though can't recall where... What do you suggest as trench mesh for a 500mm wide footing? Looks like the options to buy are either 600mm wide, is it enough if I cut something like this in half and its about 300mm wide but with an 'open' end so functionally probably more like 250mm? https://www.bunnings.com.au/jack-600mm-x-5m-reinforcing-mesh-roll_p1060319
Evening @matt234
Ok, I think I have it now. You can run the retaining wall right up to the patio brick wall. (no worrying about the red distances) as to the double brick wall with the versawall, How high are you making it?
I went straight to the idea of a gabion cage with a earth filter on the inside to stop the fines enetering that cage. Free drainage as well as keeping the soil off your wall. The smaller cages Bunnings sells in a few different sizes. Incredibly easy to use and no foundation needed. (check out my bookmarks) gabion basket shows a bunch of different sizes. Definently would work well for retaining wall away from the edge of your place. Best part if you ever change your mind, need to work on them then its easy enough to remove them It would bypass a bunch of concreteing and brickwork.
Dave
Hello @matt234
Thanks for the additional information about your retaining wall project. I've had another look at the photo you posted and just realized that your garden is much higher than the weatherboard of the house. Please let me know if I'm looking at this incorrectly. Does that mean that when you push the soil back it will be at the level of your grey fence?
If that's the case, the concrete base will need to be high. Have you considered having the base installed a little higher? This will help with not having to build such a tall base footing for the retaining wall. Let me re-draw the layout so that you'll get a better idea of what I'm proposing. As soon as I'm finished, I'll post it here.
Eric
