Forum: Block Paving
Topic: Rigid or flexible
started by: SB1066

Posted by SB1066 on 11 Oct. 2019,17:36

I have been working on my driveway, sorted out the drainage and put in an aco drain. I am just finishing haunching the borders and at the stage of picking the final product to use. I have opted for block pavers from natural paving. My question is...

My driveway is on a fairly decent slope and has a bend in it (canít find a way to attach an image of my drive).Should I lay the pavers on a rigid or flexi bed?
I will mortar the first 2 edging courses and was thinking about an addition 2 rows of mortar at the bottom of the slope (before the bend) to act as re enforcement?!

Any thoughts, ideas or tips on this matter would be most helpful and cheers in advance!

Posted by Tony McC on 13 Oct. 2019,09:53
There's a thread in the Site Agent's section detailing how photies can be uploaded.

Unless it's a gradient in excess of 1:12 or thereabouts, you can use flexible construction, but plan for a series of regular intermediate restraining courses to minimise creep.

Posted by SB1066 on 14 Oct. 2019,16:22
Hi Tony,

Thank you for the response. It is in excess of 1:12 at the steepest parts. Would it be feasible to lay the two flat(ish) areas in flexible construction and lay just the slope rigid, or does that complicate the matter?

Is there an ideal mix to use?!

Thanks again

Posted by SB1066 on 14 Oct. 2019,16:30
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Posted by Tony McC on 22 Oct. 2019,12:42
I can't see anything there that would make me want to use rigid construction. As long as you have well-constructed robust edge courses, you will be fine with standard, flexible construction throughout.
Posted by SB1066 on 26 Oct. 2019,10:45
Hi Tony,

Thanks again for the response! The only concern I have is the steepest section is more like 1:8 perhaps even steeper.

I have laid and haunched the edges and will by haunting 2 edging courses as belt and braces.

A friend recommended using a full mixer of sand plus half a bag of cement to use as my screed? He used it on his drive and it seems solid.

I was also  planning on using a brush in jointing compound to finish?

Many Thanks

Posted by Tony McC on 29 Oct. 2019,12:33
Wrong and even wronger!

Flexible block paving should NEVER be laid over a sand/cement bed. It may be working now for your freind, but the driveway will not perform, or survive as long, as would a properly constrcutred flexible driveway.

And then flexible block paving should not be jointed with a brush-in mortar. It's a nonsense.

The simple rule we have followed for over a hundred years is "flexible on flexible: rigid on rigid."

If the pavement is to be flexible, then there's no binder (cement) in the bedding, and none in the jointing.

When the pavement is to be rigid, the bedding must be bound (a cement-based mortar) and so must the jointing, which should have sufficient strength to support the poaving as a whole.

I still see no need for rigid paving on your project, but I would strongly recommend intermediate restraining courses. However, if you want to use the rigid option, then you must ensure the build-up is correct, so NOT a thin scattering of sand and cement over a flexible sub-base, but a proper rigid base, with a rigid (mortar) laying course and then rigid *strong* jointing.

Posted by SB1066 on 25 Nov. 2019,01:34
Hi Tony,

Thanks again for your response. I have taken your advice and opted for the flexible method. I am incorporating intermediated restraining courses at regular intervals down the slope and then again at the bottom of the gradient.

I donít want to joint with kiln dried sand and read on this site that I can potentially use a resin slurry grout instead?

Are there any brands you can recommend for this type of driveway project?

I am planning on using 3mm spacers (I realise time consuming but they are natural stone and donít have built in spacers), is this a large enough gap for the slurry grout or should I increase to 5mm?

Can I leave a space between blocks in the intermediate restraining courses or do they need to be butted up to each other?

Apologies for all of the questions.


Posted by dig dug dan on 25 Nov. 2019,20:04
Did you pay any attention to Tony's advice? Flexible means flexible. Block paving should have kiln dried sand brushed in and nothing else!
Posted by SB1066 on 26 Nov. 2019,12:16
Quote (dig dug dan @ 25 Nov. 2019,20:04)
Did you pay any attention to Tony's advice? Flexible means flexible. Block paving should have kiln dried sand brushed in and nothing else!

Hi Dan,

Apologies if you have taken offence to my post. I have taken Tonyís advice hence why I am leaving the cement out of the bedding material and steering clear of a rigid jointing compound.

I have spent a long time Working on this driveway, reading everything I can and trying to get it right, digging to the correct depth, putting suitable drainage in, etc. Now Iím at the laying stage I would just like to know other options than using kiln dried, plus all the other questions I asked in my most recent post. I have seen a lot of driveways with sand spilling out after rain and I live in w very wet part of the country. I had read that there are flexible alternatives and was just after advice.

Again apologies if you thought I was being ignorant.


Posted by Tony McC on 27 Nov. 2019,13:51
Although some people do use bound grouts for supposedly flexible block paving, it's a bit of a nonsense= and best left alone.

There are certain, very specific circumstancces where a bound jointing medium would possible be suitable, but that is, at best, one job in a thousand. From everything you've told us, you will be best served by regular, straightforward, non-setting KDS.

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