How to fix loose patio bricks?

[Terry Pinnell]

I'm close to clueless about DIY stuff involving cement, so I'd much appreciate advice please.

The outer edge of bricks of my garden patio are falling away, as you see from my illustration.

I've bought a 20 kg bag of ready mixed cement. But I'm not sure how best to proceed after removing the dozen or so bricks. I assume I should just even out the earth and lay cement over it, before replacing the bricks on top. But roughly what depth of cement - 2 inches or so? And then just press each brick down until its top is level with the intact bricks? Presumably I should also slap some mortar on the sides of the bricks before placing them?

Or should I first pack the strip of earth with smallish stones, gravel or sand, instead of just laying the mortar directly over earth?

Although it's over 15 years old, I'm puzzled how it got to this state, as I'd assume the builder laid a foundation under ALL the bricks, including these at the edges. Maybe years of gardening has been a factor...

Terry, East Grinstead, UK

[Andy Burns]

I should think it's either just compacted grit sand under the blocks, or was dry laid grit sand plus cement, that's now hardened.

but if you haven't got proper concreted-in edge course, you're going to have problems from the blocks walking.

[ss]

My understanding is that the outer brick should be set in some sort of strip foundation and this stops `it` and the rest of the block from walking. Hopefully someone with experience of monoblock will answer more fully.

[Andy Burns]

has chapter and verse, but the outer blocks need at least half their depth bedded into 4" of concrete

[tabbypurr]

If they're only bedded onto earth, you can simply put a bit more earth down there, whack it down to compact & place the bricks back on top of it. That should last you another 15 years.

The other way is to whack/compact the earth, put a couple of inches of ceme nt/sand mix down, lay the bricks on it, wiggle them into place & trowel a s mooth sloped outer edge to the mortar. Leave it all to set undisturbed for several days - it will have zero strength until day 4. Then fill the gaps b etween the bricks with a mix of cement & kiln dried sand, just brushing it in gently. Yes it does need to be dried sand.

TBH since its lasted ok on earth I'd probably just do the earth option.

NT

[harry]

With patios the norm is for the edge/perimeters to be firmly secured ideally on a concrete footing with benching. The centre is laid on hardcore topped with sharp sand. So whoever laid them was a wanker of the first order.

So you can either bodge it again or take it up and do a proper job.

[Brian Gaff]

Obviously cannot see the picture, but normally there is a piece of edging around the ,um edges, deeper than the bricks that retains them in the correct places. Brian

[Andrew]

Thermal expansion and contraction is your problem. The edge blocks or bricks need to be well constrained and if exposed to midday sun, you need to allow for expansion.

try Cormaics 'Paving expert' web site for more info.

[Andrew]

There are plastic L shaped devices that can be 'nailed' into the ground to provide edge restraint for block paving.

A slabbed patio on a proper base generall;y doesn't have the same issues.

[Andy Burns]

Yebbut slabs are heavier than blocks, and are often set onto daubs of mortar, rather than just sand.

[Terry Pinnell]

Many thanks, greatly appreciate all of that helpful advice.

Postponing action while the sun shines and instead relaxing with the Sunday papers!

Terry, East Grinstead, UK