Bedding mixes for laying paving - Advice needed!

[SketchUpMonkey]

Hi all,

I posted the following on Landscape Juice Network yesterday:

"I'm about to do a job which involves laying a large amount (95m2) of 900 x 600 x 20-25mm slate/black limestone paving and I am asking advice on what mortar mix to use in this and general paving jobs.

Don't get me wrong, i'm no novice when it comes to laying paving, I will do a 'first class' job and I won't have any 'rockers', but I do find laying paving very frustrating sometimes and know there must be better ways to do it.

My current mix is 5:1 sharp sand to cement (mixed pretty wet so it is workable) laid straight on to compacted type 1. I'm sometimes a bit 'naughty' and add a small drop of washing up liuqid as a plasticisor. I 'hand mix' myself using a battered old electic Belle mixer which I bought of a retired builder for £50 five years ago.

I was thinking about introducing soft (builders) sand into the mix as I think it may help give me a nice buttery texture, but I am concerned that it may comprimise the strength. I'm also crap at getting the water ratio right and often have to 'f**ny about' with the mix.

What's the concenssus out there?

P.s. jointing motar mixes/techniques aswell please!"

The general concensus was that I should stick to sharp sand only, beef up the mix to 4:1, keep it wet and lay each paver individually on it's own bed. Mix additives were reccommended as was sealing the paving after laying and sand filling the 'butted joints'.

However, I had a quick look on pavingexpert.com yesterday and I posted the following reply:

"Change of plan, been on Paving Expert,

Think I'm gonna have a bash at laying them on a 50mm thick pre-compacted screed of 6:1 (daren't risk 10:1) sharp/cement, semi-dry mix.

My mate Clive at the Handmade garden Co., told me ages ago that he has laid 20mm thick granite pavers on a screed before and had no installation/subsequent problems.

What's the concensus out there please?"

An LJN member reckons I may get 'rockers' with my proposed screeded method - do you think it will work?

"What's the concensus on here please?"

[SketchUpMonkey]

UPDATE!

Having talked to Nustone, they recommend that Slate is preferential over black limestone and theirs is 20>25mm thk.

Having Looked at the slate paving section on paving expert, this makes it a 'tile' and thus I should lay them on a bed of 'class IV' mortar (soft sand).

Bearing this in mind, I think I should explain the job a bit more and spiel out what I am now thinking!

The Job

The paving is going in-between a new 21m long house extension and a retaining wall 3.3m away (parallel) and then turns 90 degrees at both ends to run along the house walls. The paving is to be laid so the long length (900mm) runs away from house towards the ret. wall on a slight fall. A 300mm strip is to be left along side of house and wall to avoid r.w.p. gullies and provide a channel for drainage/lighting ducting and is to be gravelled. The main problem with with job is the fact that the extension/wall have been dug out of what was previously a 40 degree bank and the solid chalk bedrock was only 400 mm below the surface. We now have a pretty flat site with approx. 80-100mm construction depth to get the paving in. The base is solid chalk/concrete spillings/type 1 and may need some light machining to get uniform.

What I am thinking now is a 'b**tard lovechild' of both the screeding method and the class IV method.

This may involve, scalping the existing chalk to a uniform level with a 'micro digger' (access is crap), screeding a compacted sharp sand/bound bedding over the site (as the smallest sub-base I can get is 40mm down) and then lay the pavers onto this via. a class IV bed.

p.s. the existing chalk comes us in massive slithers if disturbed so I really do not want to excavate the area any deeper!

Does the last method sound advisable?

[dig dug dan]

firstly, there is no need to asterisk the word fanny.
Fannying about is a technical term used by many, and in fact, i often allow a days fannying when pricing a job. we all love a bit of fanny on here

Anyway, back the the point in hand, from experiance, slate pavers are a nightmare to stick to the bedding layer.
You need a slurry mix (which the gaffer has mentioned on a thread once before).
Get in touch with easipoint, as they might be able to help, and they can sell the correct pointing mixture too

[SketchUpMonkey]

firstly, there is no need to asterisk the word fanny.
Fannying about is a technical term used by many, and in fact, i often allow a days fannying when pricing a job. we all love a bit of fanny on here

Anyway, back the the point in hand, from experiance, slate pavers are a nightmare to stick to the bedding layer.
You need a slurry mix (which the gaffer has mentioned on a thread once before).
Get in touch with easipoint, as they might be able to help, and they can sell the correct pointing mixture too

The asterisk in fanny was there in my LJN posting. There's a lot of the fairer sex on there and I did not want to offend. I too like fanny, its a lovely old ladies name

Thanks for the advice re: slurry mix.

[Tony McC]

We've laid two trial patios in the last month using imported slate and two different laying methods, but as it's still being written up for the commissioning company, I can't say too much just now.

However, laying onto a screed required strictly calibrated paving (forget about whether it's a tile or a flag: that's irrelevant to the matter in hand) and most of the slate is too variable in thickness to allow use of a screeded bed.

Dan's point about adhesion is very important. We've been using a slurry of OPC + SBR as a bond bridge between underside of slate and the bedding, regardless of which laying method we used. My pet contractor was pretty much of the same opinion as meself that, for anyone experienced, laying onto 25-50mm of moist-to-wet mix sharp sand mortar at 6:1 is the preferred method. If the mix is too wet, flags slip, slide and float; if it's too dry, you can't get compaction and the adhesion becomes questionable.

[SketchUpMonkey]

Hi thanks for the replies,

The job in hand is 'on hold' at the moment as the customer does not think they are getting value for money from me. The slate has gone out of the window and it has been replaced with the cheapest of the cheap 450x450x32mm grey conc. slabs. These are friends/long time clients of mine and I quoted them circa. 3.4K to lay 94m2 of the cheap flags (no digging out/skipping to do).

I've recently read a thread on LJN from landscapers saying that they charge £50-£80 per m2 + cost of pavers to lay. Using this logic my quote should have been circa. £5.5k to £7K which I know would have been laughed at by the Client. :O

[lutonlagerlout]

well its their choice,
you pays your money, you takes your chances, as they say.
I had a guy baulk at my price for installing some steelwork in his house,6 months later (with no drop in price here) he has come back like the prodigal son and would like it done ASAP.
3.5k for 100M seems cheap
LLL

[simeonronacrete]

We have a range of polymer modified cementitious bedding mortars for making sure that what is stuck stays stuck. If there is a downside, it's trying to get it up afterwards if you change your mind!

Opt for prebagged or site batched depending on your preference, budget, convenience.

Have a look at Ronabond Bedding Mortar (prepacked), and Ronafix Mix A and C (site batched).

We use sharp sands, not soft, and polymer : cement bonding primers rather than PVA or cement:water.

Ronacrete Bedding and Bonding Mortars