Weekend Project
Justin Newcombe's tips on outdoor DIY projects

Weekend project: Schist happens

By Justin Newcombe

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Justin Newcombe's stony features have been getting many compliments.

Justin's schist-enhanced landing means he can look forward to drier feet this winter. Photo / Steven McNicholl
Justin's schist-enhanced landing means he can look forward to drier feet this winter. Photo / Steven McNicholl

I've had tons of positive comments about my smart new lawn and particularly about the mowing strip. Not that the grass doesn't look good on it own, in fact as each day passes it's looking better and better. But still, most of the compliments seemed to be lavished on the schist border.

As things have panned out I've found I needed a small extension to the mowing strip. So I'm going to use the same process to make a small landing that will save me from having to stand in a muddy puddle every time I get out of my car during winter.

You can use this technique on any standard or exposed concrete, as a path or even as a patio. Use any decorative stone you like - I've repeated the same small schist pebbles.

An important aspect to this technique is that it uses two types of concrete: a standard BM 20 builders mix, topped by a plaster and oxide mix. The builders mix gives the finished concrete strength, while the plaster oxide mix is perfect for bedding the stone into. Importantly, the plaster and oxide mix must be applied when the builders mix layer is still wet.

This way they key together well and won't separate later. I used 500g of oxide for every 30kg bag of plaster; it appears at first to be too black but over a couple of weeks will dry to a natural stone colour. Bagged plaster is great because it sets really hard and I never have to worry about mixing ratios. This is a pretty simple project which, depending on the area you are covering can be completed in an hour or two and requires only minimal preparation.

Step 1

Excavate 100mm down making sure the ground is flat and even. Box borders that are not already hard surfaces like concrete or timber. If you're doing a curve like I am here, use a strip of ply but use plenty of pegs too keep the shape true.

Step 2

Compact base course. Depending on the ground you may need to excavate and add more base than I have here.

The ground I'm working on is very hard and stable so I've gone over the top with a minimum 25mm layer. Wet the base before placing the concrete.

Step 3

Mix up a batch of builders mix in a wheelbarrow. A tip here is to mix the cement and builders mix together before you add the water. Next shovel the concrete on to the base and smooth out a 50mm pad.

Step 4

Clean the barrow and mix the plaster and oxide together.

Next, add the water in small amounts until you get a wet icing consistency. Apply a 20mm layer over the wet concrete.

Step 5

Add the decorative stones as soon as the plaster layer is installed. The stones need to be tapped in place so a wet seal forms around the middle. Each stone should be submerged up to its equator. Keep your hands clean as cleaning the stones is laborious. Don't walk on the stones for at least three days and wait seven to 10 days before removing the boxing.

- NZ Herald

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