mudgudgeon
Active Member
I have been experimenting with ways to waterproof render.
I'm in the process of building a large indoor enclosure that will have a large water feature in it. I want the render to be waterproof without having to seal it once completed.
I may still seal over it, but for what I want to achieve, its safer to not be reliant on a sealer coat as the only means of water proofing.
So, as an experiment, I built this. It's a waterproof food bowl with a hide underneath.
This was a quick experiment, I spent a total of about 3hrs on it.
It is 100% waterproof (tested for a few hours)
Here's what I did.
Cut out the basic shape, I used polystyrene, then use heat gun and butane pencil torch to shape it more. (no pics)
Mix up render, instead of mixing with plain water, I used a water/Silasec mixture.
Mix Silasec with water first, I used 25% Silasec, then mix render using water/silasec mixture.
Silasec is an additive for making cement waterproof. It's made by Bondall, and available at Bunnings.
I used acrylic render, but the same could be done using tile grout, or cement render.
Render your foam base.
This is mainly an experiment, so I've just done one thick coat. Normally, I'd do two or three coats.
Add texture to the final coat. I used a coarse car washing sponge on this to add some texture, also used a dust brush on part of it.
To form the bowl, I cut an over-sized hole, then filled it with render, the pushed a cereal bowl into the wet render. There is about 15mm of render around the bowl.
I sprayed the bowl with cooking oil, then covered it in cling wrap first. It's important to do this so the bowl will release from the render.
The same could be done using a tupperware container.
Here's the bowl set in the render (pop it out after the render has had a few days to harden)
While the render is wet, I coloured it with various oxides.
I sprinkle, or throw the oxide on it to spread it without damaging my textures.
This gets messy, so be careful where you do it.
It helps to use a spray bottle to moisten the render first, or after sprinkling oxides. You need some moisture the oxides soak into the render.
Try to mimic natural colour of rock, I use browns, yellows, black, terracota etc. I did this on plain grey render base, but have previously mixed oxide into the render to give a brown base, then sprinkle oxides on to add texture and colour. At this stage, the oxides aren't showing their true colours, it takes moisture to resolve the oxides, and once completed they will be paler.
Let it sit and dry off for a while.
I then lay a cut open plastic bag over it and used a sponge to smooth over the whole thing with plastic begin place. I did this to press the oxide into the render a bit without smearing it everywhere, and also did this to soften some of the texture I added earlier.
Now let it dry for a few days.
At this stage, I don't know what I'm getting in terms of final colouring of the render, its a bit of a lucky dip, It's a bit of a random process.
Once it hardened, I carefully popped the bowl out.
Then took it out onto the lawn and hosed all the excess oxide off, I scrubbed it lightly, and hosed it until no more oxide was washing off.
That's it, finished.
I filled the bowl with water before I hosed it and left it for a few hours, there was no sign that water had soaked in at all. The water beaded and ran off the render (It would normally soak in instantly)
Testing, bowl section full of water.
Finished, one waterproof feed bowl/hide.
In use. My male EWD has been burrowing under it while I've been posting this :-D
I'm in the process of building a large indoor enclosure that will have a large water feature in it. I want the render to be waterproof without having to seal it once completed.
I may still seal over it, but for what I want to achieve, its safer to not be reliant on a sealer coat as the only means of water proofing.
So, as an experiment, I built this. It's a waterproof food bowl with a hide underneath.
This was a quick experiment, I spent a total of about 3hrs on it.
It is 100% waterproof (tested for a few hours)
Here's what I did.
Cut out the basic shape, I used polystyrene, then use heat gun and butane pencil torch to shape it more. (no pics)
Mix up render, instead of mixing with plain water, I used a water/Silasec mixture.
Mix Silasec with water first, I used 25% Silasec, then mix render using water/silasec mixture.
Silasec is an additive for making cement waterproof. It's made by Bondall, and available at Bunnings.
I used acrylic render, but the same could be done using tile grout, or cement render.
Render your foam base.
This is mainly an experiment, so I've just done one thick coat. Normally, I'd do two or three coats.
Add texture to the final coat. I used a coarse car washing sponge on this to add some texture, also used a dust brush on part of it.
To form the bowl, I cut an over-sized hole, then filled it with render, the pushed a cereal bowl into the wet render. There is about 15mm of render around the bowl.
I sprayed the bowl with cooking oil, then covered it in cling wrap first. It's important to do this so the bowl will release from the render.
The same could be done using a tupperware container.
Here's the bowl set in the render (pop it out after the render has had a few days to harden)
While the render is wet, I coloured it with various oxides.
I sprinkle, or throw the oxide on it to spread it without damaging my textures.
This gets messy, so be careful where you do it.
It helps to use a spray bottle to moisten the render first, or after sprinkling oxides. You need some moisture the oxides soak into the render.
Try to mimic natural colour of rock, I use browns, yellows, black, terracota etc. I did this on plain grey render base, but have previously mixed oxide into the render to give a brown base, then sprinkle oxides on to add texture and colour. At this stage, the oxides aren't showing their true colours, it takes moisture to resolve the oxides, and once completed they will be paler.
Let it sit and dry off for a while.
I then lay a cut open plastic bag over it and used a sponge to smooth over the whole thing with plastic begin place. I did this to press the oxide into the render a bit without smearing it everywhere, and also did this to soften some of the texture I added earlier.
Now let it dry for a few days.
At this stage, I don't know what I'm getting in terms of final colouring of the render, its a bit of a lucky dip, It's a bit of a random process.
Once it hardened, I carefully popped the bowl out.
Then took it out onto the lawn and hosed all the excess oxide off, I scrubbed it lightly, and hosed it until no more oxide was washing off.
That's it, finished.
I filled the bowl with water before I hosed it and left it for a few hours, there was no sign that water had soaked in at all. The water beaded and ran off the render (It would normally soak in instantly)
Testing, bowl section full of water.
Finished, one waterproof feed bowl/hide.
In use. My male EWD has been burrowing under it while I've been posting this :-D
Last edited:
Great work!
