How to make faux natural stone out of concrete

Jenny_Aster

It's time to start building a small pond or drinking hole for birds and other little creatures.

My plan is to fully sink a large plastic (52D x 52W x 39H centimetres) trog (handles removed) into a new flowerbed. Inside, down one side, will be a few small stones stacked so any little creature that falls in will be able to climb out.

To hide the rim of the 'pond', I want to make some concrete stones which hopefully I'll be able to make them look like natural stones.

The pic below looks something that I'm looking for, but less rigid and formal, I'd like round corners with soil between the stones.

I see there's such a 'thing' as fibre reinforcement you can add to a concrete mix to make it stronger and to stop it from cracking. I also note there's a dye I could add to the concrete to give it a bit of a natural stone blend.

Think also a bit of peaty matter can be added to the concrete mixture which will help age the 'stones'.

Has anyone had success with what I'm trying to achieve? Do you have recipe? Do you have any tips or anything I should be wary of?

Thanks for any help

Obelixx

What you need is a recipe for hypertufa and some plastic lined wooden moulds in which to set it so you get a regular shape and thickness.  Have a read of this

https://blog.thompson-morgan.com/making-hypertufa/ 

and this

https://leavesfrommygarden.co.uk/how-to-make-a-hypertufa-trough/
 

BenCotto

I can’t help thinking real stones would look so much better than fake ones. You can buy them for not much money in garden centres or, better, ask on Freecycle, Nextdoor.com etc if anyone has a dozen or so flat stones they would donate. Round here, you could easily find discarded stones by the road side or by paths especially if there has been some digging going on. Alternatively ask a stonemason if they could source stones for you. 

Fairygirl

Geoff Hamilton often described his method of making rocks from concrete, just using a hole lined with plastic. I expect you could do something similar quite easily - especially as there are ready made mixes available now, but if it's only smaller rocks and stones you need, many builders' merchants stock various sizes, and even places like B&Q, or GCs as @BenCotto says. 

I don't know how much stock there is of concrete mixes now - it was all in very short supply last year. I struggled to get a bag of Postcrete or one of the ready mixed concretes for a post I needed to replace, so I had to mix my own again. 

raisingirl

Cement was in very short supply at the end of last year but seems to be easier to get hold of again now. I don't know whether the pre-mixes have reappeared but the ordinary bags of cement have. If you get a bag of cement, open it, use a bit, put the rest in the shed and forget it for a few months, you'll get something that looks like a bag shaped rock. I wouldn't recommend it, as it lacks finesse, but my point is that cement will do the work for you, you just need to mix it with something the right colour and consistency and some water.

If you want to make ones that look like your pic, you ideally need to include some lime in the mix and also be careful about the sand colour you get, as that affects the end result more than anything. You can mix soil in - making 'mudcrete'. The more non standard additions you include, the weaker the concrete will be, on the whole. You can go too far and it won't hold together at all but short of that point, weaker concrete is a good thing for what you want, as it will weather a bit and look a lot less like a breeze block and more like a stone. 

The formwork is also key. If you use a wooden box, the result will be smooth and square. If you use a cardboard box, it'll probably sag a bit under the weight and you'll get something more like a stone trough, a bit curvy. If you want rocks, as GH suggested, an irregular hole in the ground with or without a plastic liner will give you rock like shape - unlined it'll have mud and stones stuck to it which may be good and may be bad, depending on the look you're aiming for. Any of those, once painted with runny yoghurt, will grow lichens and moss and begin to look stony very quickly, especially close to a pond and particularly if you let plants grow around and between so the 'stones' recede a bit into the background.

I doubt you need the fibre additions - that's for structural concrete which your rocks wouldn't have to be.

Jenny_Aster

Obelixx said:

What you need is a recipe for hypertufa and some plastic lined wooden moulds in which to set it so you get a regular shape and thickness.  Have a read of this

https://blog.thompson-morgan.com/making-hypertufa/ 

and this

https://leavesfrommygarden.co.uk/how-to-make-a-hypertufa-trough/
 

Well there's a new name for me to try and remember .... hypertufa. I saw one of these hypertufa troughs that had aged really nicely, the compost in the mix being a great medium for lichen to grow

BenCotto said:

I can’t help thinking real stones would look so much better than fake ones. You can buy them for not much money in garden centres or, better, ask on Freecycle, Nextdoor.com etc if anyone has a dozen or so flat stones they would donate. Round here, you could easily find discarded stones by the road side or by paths especially if there has been some digging going on. Alternatively ask a stonemason if they could source stones for you. 

Agree, and I can't help thinking I'm 'over thinking' this  will do some research now you've given me a couple of ideas.

Fairygirl said:

I don't know how much stock there is of concrete mixes now - it was all in very short supply last year. I struggled to get a bag of Postcrete or one of the ready mixed concretes for a post I needed to replace, so I had to mix my own again. 

Think the stocks may have been replenished, looking at B&Q's website they look to have good stocks.

Thank you for your help, it does look like I've been a bit obsessed with this picture in my mind, think I'll need to be more open minded. In truth I don't really think I'm a fan of this faux stone - just realised the title of this thread is a bit of an oxymoron isn't it   

Fire

Making faux stone was featured on GW

https://www.bbc.co.uk/programmes/p02w7nfj

AnniD

So many people remember Geoff Hamilton making "fake rocks" years ago, l certainly do, but there doesn't seem to be any record of it on the Internet. 
I have visited Barnsdale twice, and each time my OH and l gazed upon those "rocks" as if they were the holy grail. I could hear Geoff's voice in my head 😊.
https://barnsdalegardens.co.uk/artificial-rock-garden.html

Jenny_Aster

raisingirl said:

Cement was in very short supply at the end of last year but seems to be easier to get hold of again now. I don't know whether the pre-mixes have reappeared but the ordinary bags of cement have. If you get a bag of cement, open it, use a bit, put the rest in the shed and forget it for a few months, you'll get something that looks like a bag shaped rock. I wouldn't recommend it, as it lacks finesse, but my point is that cement will do the work for you, you just need to mix it with something the right colour and consistency and some water.

If you want to make ones that look like your pic, you ideally need to include some lime in the mix and also be careful about the sand colour you get, as that affects the end result more than anything. You can mix soil in - making 'mudcrete'. The more non standard additions you include, the weaker the concrete will be, on the whole. You can go too far and it won't hold together at all but short of that point, weaker concrete is a good thing for what you want, as it will weather a bit and look a lot less like a breeze block and more like a stone. 

The formwork is also key. If you use a wooden box, the result will be smooth and square. If you use a cardboard box, it'll probably sag a bit under the weight and you'll get something more like a stone trough, a bit curvy. If you want rocks, as GH suggested, an irregular hole in the ground with or without a plastic liner will give you rock like shape - unlined it'll have mud and stones stuck to it which may be good and may be bad, depending on the look you're aiming for. Any of those, once painted with runny yoghurt, will grow lichens and moss and begin to look stony very quickly, especially close to a pond and particularly if you let plants grow around and between so the 'stones' recede a bit into the background.

I doubt you need the fibre additions - that's for structural concrete which your rocks wouldn't have to be.

Thank you  a great post, you've set me off again now with further ideas. As the 'stone' is setting I'm thinking I could make a 'natural' looking hole/space between the stone to plant a creeping plant such as Aubretia, Forget-me-not, poached-egg plant.

Jenny_Aster

Fire said:

Making faux stone was featured on GW

https://www.bbc.co.uk/programmes/p02w7nfj

Thank you for the vid, he makes it look so easy. I'm sure to make an alpine trough now 

Fairygirl

Troughs and planters are quite easy -you just need some basic shuttering as @raisingirl says. That can be something you make yourself with pieces of timber, or a wooden crate or similar. As long as you have enough space between the two layers, you'll get a reasonable outcome. You can do planters too, with different sized buckets or basins. 

As you're not using anything very big for your pond, I'd think it isn't worth making stones/rocks though.