Gravel on concrete

[toshj]

Afternoon.

We're in the process of updating our garden, and one of the final areas that we need to address is a small area between the back of the house and one of the patio areas. We've left the patio raised by about 50-60cm (it was initially about 150cm) as we've a north facing garden and the area therefore gets good sunlight in the morning.

The old existing concrete laid many years ago seems in good condition - the patio has a several run off points into a lowered channel that deposits into a soak away.

I've read that you should look to avoid laying gravel directly onto a concrete slab as it can cause the stones to move underfoot and is a bit of a hazard. The area is quite small - 3.8m x 1.5m - and is rarely used. Our plan was to put down something like Cotswold buff gravel and I was wondering whether I needed to prep the area before laying the stones down? We're likely to be a couple of raised planters on it when complete to act as a mini-barrier so that people don't fall off the patio!

There's virtually nothing in terms of weeds coming through the concrete itself (just one or two near the edges) and the slab is angled down to the channel to provide good run-off. There's also a 5cm-6cm step up at the end nearest the door, and I was hoping this would help contain the stones somewhat or at least prevent them from rolling around when stepped on.

 

[b0rn2sk8]

Cotswold stone is quite angular so you may get away with it but if it does move underfoot, it will really move. You could give it a go if you are not really walking on it. To mitigate movement you could put down a gravel grid or putting a layer of something soft like sand to hold the stones in place but you don't look like you have the depth.

Is the slab at a consistent level length ways? You could continue your slabs along it and leave the channel open for drainage. To me that would seem to be the best option.

You could hide the slab under decking (wood or plastic) but I think I'd prefer the slabs and they would be far less maintenance.

 

[cadmunkey]

Why not just lay some slabs? You have some spare in the pic

 

[Delvis]

Why not just lay some slabs? You have some spare in the pic

I didn't notice that....I'm going to presume they're allocated already mind! Otherwise yes, just slab.

 

[toshj]

Cotswold stone is quite angular so you may get away with it but if it does move underfoot, it will really move. You could give it a go if you are not really walking on it. To mitigate movement you could put down a gravel grid or putting a layer of something soft like sand to hold the stones in place but you don't look like you have the depth.

Is the slab at a consistent level length ways? You could continue your slabs along it and leave the channel open for drainage. To me that would seem to be the best option.

You could hide the slab under decking (wood or plastic) but I think I'd prefer the slabs and they would be far less maintenance.

Thanks! My wife has vetoed the use of those slabs because a) they're heavily used in other areas of the garden and she's keen to ensure it doesn't look like the space is almost entirely sandstone slabs and b) she's obsessed with the notion that someone is going to fall off this raised patio and that gravel will somehow break their fall...

I was looking at the gravel grid but, as you say, not sure we've got the depth for it. Think I might just lay the gravel on top of the concrete slab and see how we get on. It wouldn't be the most expensive mistake if we got it wrong... although it was be a pain to clear it back out again!

 

[Quartz]

How about laying some hot tar on the concrete, then laying a shallow layer of gravel on top of that so you have an immovable base layer, letting it cool, then laying more gravel?

 

[Terminal_Boy]

Having fallen off things onto gravel in the past, I can’t recommend it as an energy absorbent surface. As it’s on top of concrete, the gravel won’t absorb much and will just add a bunch of small cuts to the rest of the injuries.

 

[toshj]

I've explained to my wife that gravel is going to hurt just as much as anything else but... you know.

 

[Terminal_Boy]

I've explained to my wife that gravel is going to hurt just as much as anything else but... you know.

All too well.

 

[b0rn2sk8]

Haha yeh, I’d say falling onto the gravel would be worse than slabs…

 

[sja360]

I've got gravel over some concrete at the back door, it ends up moving so yeah not ideal. Its only less than an inch deep.
Depends if you're just walking on it or planning to use a ladder etc. As walking on it should be fine.

A good suggestion is to continue laying the slabs.

 

[Dalandius]

If your wife is worried about someone falling off the raised patio on to it you could use one of the many play safe surfaces, which are designed to be safe to fall on.
I searched "play surface for garden" and this came up with quite a few solutions.

 

[drew]

I put gravel over concrete, it just got really grotty in the end as all the detritus built up. I'd advise against it

 

[Delvis]

Tbh if you don't slab that it's going to look like you just ran out of slabs and put gravel down

 

[gpuerrilla]

Having fallen off things onto gravel in the past, I can’t recommend it as an energy absorbent surface. As it’s on top of concrete, the gravel won’t absorb much and will just add a bunch of small cuts to the rest of the injuries.

 

[Bunka]

Have you considered a small area of decking? You could potentially run it up the brick face of the retaining wall as well, add some planters etc. Gravel will end up becoming a mess of weeds, composting leaves etc.

 

[potatolord]

Gravel on concrete will be painful to walk on in bare feet, especially if you have flint chips or similar. I speak from experience.

Also, it will clog up with muck over time.

 

[toshj]

Thanks for the advice all. I hadn't really thought about muck building up in it - I'd thought the decent drainage would take care of that, but it seems not.

TBH, no one is going to fall onto it anyway as there will be quite wide raised planters next to it. Decking sounds like a possibility, but it doesn't get an awful lot of sun and could quite easily deteriorate quickly. Using the extra slabs might be the only way to solve it, but it really will make the garden look very "stoney"

 

[Delvis]

Thanks for the advice all. I hadn't really thought about muck building up in it - I'd thought the decent drainage would take care of that, but it seems not.

TBH, no one is going to fall onto it anyway as there will be quite wide raised planters next to it. Decking sounds like a possibility, but it doesn't get an awful lot of sun and could quite easily deteriorate quickly. Using the extra slabs might be the only way to solve it, but it really will make the garden look very "stoney"

As opposed to stone broken up small?

 

[Mysterae_]

How about binding in epoxy?

Edit - resin looks better suited.

 

[toshj]

As opposed to stone broken up small?

Yeah, the stone we have in the garden is like a drab grey whereas my wife wanted light coloured gravel to add a bit more "pop"... I've talked her round though and she seems to be onside with a different route.