I have an outdoor area which is currently pebbled and retained next to a fence. I plan on removing the pebbles and turfing, and am also considering planting a green hedge because I don't like the look of the fence. The problem is the current retaining wallhas a large gap AND is on an incline ( at the junction of the front and back of the property). To complicate things, the floor of the gap is cement. I'd like to close that gap to allow for my plans above, with the possibility of creating a small retained garden bed against the fence for my potential hedge. I think the pictures will do a better job of explaining the situation

I think the "easiest" solution is to just fill the gap with soil and turf over it, but I feel as though the moisture of the soil against the fence will accelerate rot, and I have some mild worry about the soil pushing against the fence. I'd prefer to build something that will prevent these 2 problems, and I think a retaining wall is the right solution, but am unsure. The issues with building a retaining are that (1) the bottom of the gap is concrete (which makes putting posts in for a retaining wall complicated I think), (2) the gap is narrow on the front end, and (3) there is a significant incline which makes putting in a level retaining wall more difficult.

I'd be grateful for any advice/recommendations.. Thanks!

From front looking back The gap at its widest and deepest. Foot for reference

  • Is the fence yours, or your neighbor's?
    – Ecnerwal
    Commented Jan 25, 2022 at 13:40
  • Neighbour's fence Commented Jan 29, 2022 at 10:30
  • Then you definitely don't want to be piling dirt or stones against it.
    – Ecnerwal
    Commented Jan 29, 2022 at 15:06

2 Answers 2


Fill with dirt will be a fail. Yes, that will rot and push out the fence, so don't.

Concrete block wall would be the way to do this, with the bottom blocks cut and mortared to get it level on the slope, and drilling holes to grout in rebar to attach it to the concrete below. Since you won't be looking at it with the fence there (and it's pretty short) I'd just use plain mortared concrete block, not fancy free-stack landscape blocks that will be harder to cut.

Working-space wise, you're going to have to dig out and pile to the left to make room to work, then move stuff back when the wall is done. You can keep your stone pilled separately and use it for a drainage layer on the bottom (be sure to put in weep holes at the bottom of the wall for drainage as needed.)

  • Right, so rebar just the first layer into the existing concrete? would each block need a rebar or just intermittently? I've not done any concrete work, but given this is hidden and relatively small, I might give it a go Commented Jan 25, 2022 at 15:32
  • Rebar is relatively inexpensive, your wall appears to be relatively short, I'd put the rebar tall enough to reach the top course of blocks. That's harder to justify on a tall wall, as lifting the blocks over them becomes tedious. Might well pin every core-hole on the taller sections, as the wall gets shorter (less pressure) you could probably get away with less, but rebar is still relatively inexpensive, so I'd probably keep right on pinning them.
    – Ecnerwal
    Commented Jan 25, 2022 at 16:09
  • The way prices have gone the last 2 years, nothing is "cheap" anymore, but more rebar now is less expensive than redoing the whole thing later, too.
    – FreeMan
    Commented Jan 26, 2022 at 13:10

Don't put earth touching timber, it won't last long.

Anyway, how about filling that gap with the pebbles you already have. That would not rot the wood, and would probably look nice. And cost nothing ;-)

Yes, the pebbles you have are a bit small. I have a similar gap between house and garden all the way around (this is central Europe, we have weather) and it is filled with large pebbles, 8 - 20 cm.

People solve the problem of pebbles obeying gravity by inserting flat stones (even old roof tiles) or sheet metal, vertical along the sides or in the middle of a slope, to keep them in place. Wood will not do. No matter what it's treated with, if it gets wet regularly it won't last a decade.

  • Rain is likely to wash the pebbles through the fence and the large gap below the fence in the 2nd picture.
    – FreeMan
    Commented Jan 25, 2022 at 13:50
  • 1
    I can close the gap there with some treated timber to prevent pebbles leaking out of the back. The side fence has no gaps. However I still worry about structural integirty of the fence with a stack of pebbles pushing against it... Commented Jan 25, 2022 at 15:30
  • 1
    Sheet metal will end up rusting. Galvanized steel will last a lot longer but cost more. More stone would probably be the best bet for retention.
    – FreeMan
    Commented Jan 26, 2022 at 13:11

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