Patio construction advice

[jstrong]

Hello

I've just started constructing my patio (will be using Indian sandstone with West Hoathley bricks frog side down for the edging) and so far have excavated and created a 75mm type 1 sub base.
In order to prevent lateral movement I have excavated a perimeter strip to a depth of 200mm below the finished surface level and partially filled with 95mm of concrete thus allowing 105mm for the depth of the edging brick (65mm) and 40mm for the mortar bed. Can anyone see any problems with this method? Will I have a problem with frost penetrating this 40mm mortar bed and possibly lifting the bricks in freezing conditions?

Also any advice on the ingredients for the bedding and pointing mixture would be appreciated.

 

[r896neo]

to be honest the bricks would have been better layed and haunched with concrete. You will find it hard to bed them on 40mm of concrete now so will have to use mortar. Make it good and strong like 3 or 4:1.

The stone should be layed on a full wet mortar bed of 25-50mm depth.

The mortar should be grit/sharp sand about 5 or 6:1 and mixed up to similar consistancy to brick-laying mortar (a fraction stiffer)

You'll need a good drop of plasticiser in it to give it some just folllow instructions on the label.

Personally i add a good dose of sbr (100ml) to every mix for natural stone as it aids adhesion when using sand with no fines. Many don't bother but for the added cost of 20 quid over the whole patio why risk it.

As for pointing a damp mix of plastering sand 4:1

 

[jstrong]

r896neo
Many thanks for your reply.

Can I ask why you'd use plastering sand rather than building sand, it's just that I've got near-on a jumbo bag of bdg sand that I could do with using somewhere on the project!
Also would it be ok to lay the whole patio and then point up afterwards?

Cheers

James

 

[r896neo]

Many people point with building sand. Personally i feel plastering sand gives a harder joint and also it is less likely to stain the paving as you point because it doesn't hold as much water.

Don't use building sand for the laying but you could mix it in with grit/ sharp sand about 60:40 sharp to building. If you do this you'll need to make it a touch less wet as building sand can really turn to slop when tapping flags down into it.

Its much easier to lay it and then stay off it to let it go off then point up 2 days later if you have time to leave it. You can get on it the next day if needed but stay in the centre of large flags only.

 

[jstrong]

r896neo

Many thanks again for your input, it's very much appreciated.

Just one more quick question, would it be ok to use a normal mortar mix for laying the edging bricks? i.e. building sand and cement without adding sharp sand? Max thickness of mortar bed is going to be around 40mm.

Hoping to start this as soon as the weather clears today around lunchtime hopefully!

Thanks again

 

[r896neo]

Building sand will grip them better but is much weaker when used in such a deep bed. Because you have the concrete under there its probably fine. It also has the same problem though of tending to turn a bit to soup when you start tapping edgings into it so make the consistancy accordingly

 

[jstrong]

r896neo

Thanks again for your advice.

I managed to lay about 40 bricks this pm using a fairly stiff mix and then pointed using a 3-1 dry mix and pushing into the joints. Started raining again as I pointed the last of the 40!! Hopefully will get a few more laid tomorrow. Might post a few picks when it's all done!

I've got roughly a 2" gap between the edge of the bricks and the lawn so might pour a bit of concrete in to act as haunching, (this will sit on the concrete foundation edging strip laid just before the weekend). Will pour in just enough to pick up the first 20-30mm of the brick. Does that sound like a good idea?

 

[r896neo]

Yes you definately want to haunch them with something. Ideally you want to lay and haunch as one procedure which ties it all in as one solid lump but in your case its not so vital as there will be soil and grass packed in.

Aim to haunch half the height of the brick then fill the rest up with a mix of soil and grit sand

 

[jstrong]

r896neo

Thanks for that. Could end up being a professional job

 

[r896neo]

It's not rocket science so all you need is the right information and take your time especially with setting out and cuts etc. The devil in the the details