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How to fix gap under fence?

rebelliouskiwi

I am looking at options for closing the gap between my neighbours side and mine. Under the fenceline, there are some bricks as you can see, but they aren't close to the fence & there is a lot of weeds and grass that comes through their side onto ours.

The white timber in the soil shows where the soil / mulch will finish & so that is the space I have free, that I want to block between the white timber line and the fence. On top of the soil I am having raised garden beds. Parts not covered by raised garden beds in that area will have pebbles, still not going over the brick at the front or the white timber at the back.

Top gap is about 27cm max and bottom gap is 13cm at the smallest part.

What I was thinking was H4 timber sleeper, Google recommended ACQ, over the other which i'm assuming is CCA. Does it matter, when the plants won't really be accessing that area?

Or is there a better option? Budget is my biggest concern, but also, don't want to maintain frequently either.

What sort of layering system is recommended for the pebbles section? Currently I am trying to kill onion weed in this section, with Yates Zero. So i'm guessing I need to go quite deep with preparing once I eventually get to that stage.

Can I prepare/layer the entire area the same way, then plonk the raised garden bed on top of the pebbles? Or do I need to prep garden bed areas and pebbled areas as 2 different spaces? I am using the Birdies brand of Garden beds.

I have lots of newspaper & a few cardboard boxes for layering the area. Is that good enough for the pebbled area? Or do I need to do something better, for long term protection.

Many thanks from West of the Blue Mountains NSW region.

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EricL

Hello @rebelliouskiwi

Thank you for sharing your question about filling in your fence gap. I propose doing a general clean-up of the weeds and replacing the white timber with https://www.bunnings.com.au/200-x-50mm-2-4m-treated-pine-sleeper_p8032702 . The ground under the fence will need to be dug up a little to allow the sleeper to slide into the gap. To help facilitate drainage, I suggest putting some drainage gravel at the base of the sleepers before positioning and covering them. Once in position the soil can be put back into place. The sleepers can be secured with screws from the top of the bottom channel of the Colorbond fence.

To slow down the weed infestation you can cover the base of the sleeper with https://www.bunnings.com.au/pillar-1-8-x-10m-grey-geotextile-drainage-membrane-mat_p0126613 . Please keep in mind that the weeds from your neighbours will still find a way to pass through the gaps between the sleeper and Colorbond fence, but it will not be as abundant as before.

In regard to the raised garden bed, I agree with your choice of using ACQ (Alkaline Copper Quaternary) sleepers, these are timber logs or boards treated with a copper-based preservative that is completely free of arsenic and chromium.

I propose leaving a 100mm gap between the fence and your raised garden bed for easy access and maintenance. This gap can be filled with pebbles or gravel depending on your preference. I've placed some rendered sample images using AI below to give you an idea what the fence will look like when properly covered. The next photo is the raised garden bed placed in front of the fence.

The Birdies brand of Garden beds can be placed right over the soil and the only prep needed would be to have the area level. Placing cardboard or newspaper on the soil to control weed infestation is effective as it will eventually decompose into the soil. It would be more cost effective if you only had to surround the raised garden bed with pebbles rather than the entire area.

I also suggest looking at the Top 10 most popular raised garden beds

Let me call on our experienced members @mich1972, @Rolando, @richard_s and @Anemony for their recommendations.

If you need further assistance, please let us know.

Eric

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Anemony

Thank you, @EricL for the tag!

I love your idea of using raised beds with pebbles around them. I also agree with Eric’s suggestion of using pine sleepers to cover the gap along the fence — that’s actually what we did in our own garden.

Our setup is a little different (photo attached), but we used pine sleepers underneath the main fence, as well as along the front of our planted hedge. If you do something similar, just make sure your soil isn’t sitting directly against the fence itself.

I’d definitely recommend laying down cardboard and/or newspaper over the bare soil first, then positioning your raised beds along the fence. Once you’re happy with their placement, you can add your gravel or stones around the beds.

One thing I wouldn’t recommend is adding stones or gravel to the bottom of the raised beds for drainage. It won’t improve drainage in the way you might expect and will mostly just take up valuable growing space (and waste a lot of material!).

When it comes to filling the beds, there are a few different approaches you can use. One popular organic option worth looking into is the Hügelkultur method, which uses layers of woody and organic material beneath your growing medium. There are plenty of great tutorials online, and it can help reduce the enormous amount of soil and compost needed when filling several raised beds at once.

I share a few bits and pieces about my own organic raised-bed and kitchen gardening over on Instagram at @anemony_botanicjournal if it’s helpful to see how ours has evolved.

Hope that helps, and happy gardening! 🌱

MitchellMc

Many thanks for jumping in and sharing your experience @Anemony. It's fantastic when experienced members like yourself contribute their knowledge to discussions, particularly when you can share examples of what you've done successfully in your own garden. I trust your photo and advice will provide @rebelliouskiwi with some great practical ideas to work with .

We really appreciate you taking the time to help another member, and I hope we'll see plenty more of your gardening knowledge shared across the community.

Mitchell

richard_s

I will second what has already been said by Eric and Anemony:

I won't put pebbles down under the raised beds, it's wasted material (and costs quickly add up).

If the ground is gently sloping, you can dig in a bit on the higher side of the bed/s so that the beds sit mostly level (if desired).

May I also echo Anemony's suggestion of using the Hügelkultur method to reduce the amount of soil you need (depending on the height of your raised bed). What we did was putting tree branches, chopped up tree trunks, and even grass from the mower catcher in the bottom, and then add soil and compost on top.

However, if you plan to grow root vegetables in the bed, esp things like carrots, make sure you have enough depth of good, loose soil (before it hits your tree cuttings or other chunky organic materials).

Just my 2 cents.

MitchellMc

Many thanks for jumping in and sharing your experience @richard_s. It’s particularly helpful to hear how you’ve used the Hügelkultur method successfully and your point about ensuring there is sufficient depth of good soil when growing root vegetables.

I’m sure @rebelliouskiwi will appreciate the additional advice.

Mitchell

Noyade

G'day @EricL

Gorgeous looking AI 'after' photo above. With regards the exposed concrete - is AI suggesting chiselling away those concrete 'collars' before attempting a flush sleeper look?

Or cut a contour as eventually it won't be seen? My AI (Amateur Illustration) interpretation…

MitchellMc

Good pickup, @Noyade. Eric’s AI image is intended more as inspiration for what could potentially be achieved rather than an exact representation of how the sleepers would be installed.

As you’ve pointed out, we'd need to account for the existing concrete footings. I certainly wouldn’t suggest chiselling them away, as they are supporting the fence posts. Instead, the sleepers would need to be appropriately notched around the concrete where required.

Mitchell

rebelliouskiwi

Thank you everyone for your suggestions and images. The AI looks gorgeous! Very inspiring when I look at them all "done".

I will be cutting the sleeper, to accommodate the exposed concrete footing, @Noyade , like your own AI interpretation 😉

I forgot to say, that the stones, they are already here. I removed them from the front of my house, where we didn't want it. Possibly Cowra Gold (according to Google). So no cost involved for that. I wouldn't have bought them, but since I have them and no reason to use them anywhere else, i'll pop them here.