The Brew Cabin

Tony,

I'm the one who is creating a 40m2 imported indian sandstone patio.

All the excavation work is nearly completed and the site should hopefully be cleared by 7pm on sunday (if not I can't go to the pub)

The grit sand is coming the following friday, which will be dumped and levelled over the week and the stone hopefully the following friday.

My question is:- I was just going to lay the slabs haunched up to a concrete edge. I have just finished reading your page on timber edge and now I'm not to sure as the timber edge looks slightly easier to install.

Can you please give your advice and the costings of the concrete based on 30m of edge needed

Cheers

Chris

Maybe I'm missing summat, but why do you need an edging? Unlike block paving, gravel or tarmac, flags don't need an edging to ensure their integrity - they can manage perfectly well without one.

There's no doubt that timber edgings are easier to install, and cheaper than concrete-bedded edgings, but they aren't as secure and tend to have a shorter lifespan.

The cost of a concrete bedded edging has two components. The first is the cost of the edging itself, which can be anything from a few pence per metre if you use old, relaimed bricks or setts, up to several pounds per metre, if you opt for a fancy manufactured unit. Secondly, there's the cost of the concrete needed for the bedding and the haunching - this varies slightly, depending on the dimensions of the edging being used. A 200mm wide brick paver used as an edging needs a bed around 300mm wide, but the haunching will only be 40-50mm high, whereas a 200x50mm concrete edging kerb needsa abed only 150mm wide but the haunching will be three times that needed for blocks, at 150mm wide.

So, I'd suggest you first decide whether an edging really is necessary, and then, if it is, decide on the type.

To calculate the volume and cost of the necessary concrete, take the width of the edging, add 100mm and then multiply by 100mm. That gives a rough quantity of concrete, per metre, needed for bedding. Next, take the height of the edging, subtract 25mm and multiply that by 100mm - that's gives the volume of haunching required. Add the two together, multiply by the total length of edging required (30m in your case), multiply by 1.15 (for wastage and spread) and that gives the total volume of concrete needed to do the job. To find the cost, multiply the volume, in cubic metres, by 75 quid, which is an average sort of price for site-mixed concrete.

How's that?

Sorry

I thought all projects needed to have an "edge". i.e to stop the bedding dispersing around the garden and the flags moving.

In that light what stops the end flags from moving, if there is no edge to keep them secure, or are they held in place by there own weight

Thanks

If the bedding is cement-bound, as is the bedding mix I recommend (10:1 grit sand/cement), then it will not disperse. Full stop. The flags stay put due to their weight, as you surmise, unless they are laid to a significant gradient, in which case the edge flags would be laid on a wet mortar bed to 'anchor' them in position.

Having said all that, if you want to lay an edging to your flags, then go for it. There's nowt wrong with doing it that way, but it's not essential, which is what you seemed to think originally.

Brilliant.

My next question is would the roots of fruit tree, plum for instance, planted at the corner of the patio disturb the slabs or are the roots not that powerful. Or would you suggest, either not planting the tree, or encasing the flower bed in old slabs so that the roots cannot travel underneath the new flags

Thanks again

The roots of fruit trees certainly would disturb the paving, but it will take a few years and it could be 20 years or more before you noticed.

If youlre just about to plant these fruit trees, I'd suggest you use a root barrier membrane to line the planting pit and keep roots away from the paving. You only need place the root barrier between the tree(s) and the paving, not all the way around, and it need only extend down around 600mm or so, as once roots are deeper than that, their effect on the surface of the paving is hardly noticeable.

There's a bit about root membranes on the Geo-Fabrics page and you might like to take a look at Peter Scott's site, as they specialise in just that sort of thing.