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Posted: Mon Sep 19, 2005 8:53 am
by Sloucher
Hi,
I'm about to start laying my first (and probably last) slabs. I have a 13m2 area to cover, and I'll be using Marshalls Haworth Moor riven paving.
I've compacted the earth underneath the whole area (several times, over several weeks), and on top of that I have 2-3 inches of grit sand, also compacted. Unfortunately I wasted time making the sand layer billiard-table smooth before I came across this site and read that I need individual bedding due to the uneven thickness of the slabs, but at least I have a starting point.
My question is whether I can avoid "buttering" the slabs as I lay them and then grouting with further mortar. I've read about all the alternatives on this site, but I'm not sure which (if any) are suitable for my situation.
When I imagine the strength of 2 wide slabs connected by a thin strip of mortar, it seems like breaking the joint would be extremely easy if there was any movement in the slabs? How much stronger is the paving with mortar? And relative to that, how do the jointing compounds compare?
I wouldn't really consider doing no jointing/pointing at all, but I don't want to go all the way to buttering & grouting with mortar if it's overkill for my situation. This will be a *very* light traffic area - it'll never have to host a barbecue or suchlike.
So I see my options as follows:
1) butter with mortar and grout with mortar
2) butter with mortar and grout with "compound"
3) no buttering, fill joints with "compound"
What would you recommend?
Gary
Posted: Mon Sep 19, 2005 5:47 pm
by Sean Buxton
Gary,
Firstly I am not a contractor so my comments are based on my own experience of laying my first area of paving last year and what knowledge I have accumalated by being part of this forum.
You can decide not to butter the slabs as you lay them and return to point the patio after you have finished as I did on my project.
In my opinion, this is not a good idea. You will be faced with a seemingly never ending task. Far better to point as you go. If you do this, you will also avoid having to clear the joints of detritus which can very quickly build up if the joints are left exposed for any length of time.
With regard to buttering, I cannot comment as I didn't use this method (basically I forgot). All I can say is give it a go and see how you get on, it is the recommended method.
I ran out of time on my project and had to brush in a dry mix and then add water. I tried to "strike" the mortar but the end result was not as good as the mortered joints.
I cannot comment about using a "compound" for pointing purposes.
As I understand from comments on the site, the pointing just "fills the gaps". If the bed is right, the slab shouldn't move.
Hope this is of some help.
Sean
Posted: Tue Sep 20, 2005 6:15 pm
by Sloucher
Thanks Sean.
You say you didn't do any buttering - so do you feel your patio has suffered as a result? If not, maybe I should "forget" too! 
Is there anyone out there prepared to offer an opinion on whether using a pre-prepared mix would be a good option? And whether it would be OK without buttering, or whether I need the butter too?
The attraction of a pre-prepared mix for me is that it sounds a heck of a lot easier. I don't mind a little extra expense.
Posted: Tue Sep 20, 2005 8:07 pm
by Sean Buxton
No, the patio hasn't suffered at all. I just took care to make sure the joints were packed with as much mortar as possible.
Before pointing, I sprayed water onto the joints to reduce the drying out time of the mortar.
The patio is just under a year old, there are no rocking flags and all the pointing is still in one piece.
Posted: Thu Sep 22, 2005 12:52 pm
by Tony McC
Those riven flags look far better when pointed. However, it's your patio, and if you prefer to use a sand joint and deal with the eternal weeding issues, the that's your prerogative.
If you accept that some form of jointing is better, you can choose mortar or polymeric. Mortar is a fraction of the cost of even the simpler polymerics and is both the preferred and the traditional method of jointing stone flags. Polymeric is simple and clean, but there are problems with some of the better known polymerics, and the really good stuf isn't cheap and may well be considered 'overkill' for a patio project.
So, if you decide to go with mortar pointing, you can choose to butter and point, butter and dry grout, or leave dry and point later. Buttering helps regulate the joint width, giving far more even joints that are more completely filled, which means they are less likely to fail in the medium-long term.
For DIY, the simplest is to use a mortar butter and the top-up the joints with a dry mix while the butter is still plastic (wet and pliable), tooling the dry mix as you go to ensure a really sound joint.
Posted: Sat Sep 24, 2005 5:55 pm
by rms
We find it fast and effective to sweep, compact and sweep again a kiln dried / cement mix of about 6:1 ratio into the joints. The paving must be dry and the mix needs to be swept across the whole area as it can temporarily stain. Then fine mist the whole area with water. Leave for an hour or so and then mist again. This can be repeated several times. Note that for best results, keep the joint mix finish height just below that of the paving.
Posted: Mon Sep 26, 2005 10:09 am
by Sloucher
Thanks for all your replies. My dad and I laid the slabs at the weekend, and though we were prepared to attempt buttering, our experience with the very first slab quickly put paid to that idea.
It took so long to get the first slab stable we realised we didn't have nearly enough time to faff about with mortar, so we decided just to lay them all dry and worry about pointing later.
I'm not quite sure what the problem was (apart from inexperience - at least on my part). My dad's laid paving many times before without problems, but this was my first time, and the first time he'd attempted it with riven paving (with an uneven base).
Every time we laid a slab, it rocked badly. We'd lift it, put some sand in the rocking corners and try again - it'd still rock. On and on we went for up to 15 mins until we eventually just had to leave it "ok-ish". It really was incredibly frustrating.
I think the problem may have been the sand I'd used. It was grit sand ("granitsand" I think it was called), and it was very resistant to movement. No amount of jumping up and down on the slab (or hitting it) would make the sand settle under the slab. If I put ridges in the sand before putting the slab down, the ridges would still be there when I lifted it again. I suspect had I put in a layer of finer sand we could have settled the slabs much more easily.
Anyway, it took us all day to lay a 13m2 area, which currently remains un-pointed. We just had to accept that a certain amount of "rock" was inevitable - it was either that or give up - so I'm decidedly worried about what will happen when I point them now...
I'm hoping that if I leave it until next weekend before pointing, the rain and time will let the slabs settle in a bit - but deep down I know that's just wishful thinking!
Posted: Tue Oct 18, 2005 9:46 pm
by TOLIVER
This was very similar to my experience. Took me ages to get slabs steady and 8 months on, i still feel a few move when I walk on them, albeit only slightly. I did the wet pointing method and it took longer to point than it did to lay all the slabs. My back killed me by the end of the day.
I gave up in the end and got a builder to finish the rest.
They followed a similar method with 10:1 grit sand / cememt, but made it much damper. It was far quicker to lay and get the slabs even and the result is rock solid slabs. They dry pointed the slabs by brushing in. The pointing looks nowhere near as good as the one 's I did, but it did only taken them half an hour !
If(when) I do some more, I will make the bedding much damper(but not wet and sloppy) and wet point when theyre dry.
Has anyone used the pointing guns. I have seen some for about £30 that look like mastic guns, but you fill with wet cement.. They look quite good and may save hours
Posted: Sat Oct 22, 2005 3:58 pm
by Tony McC
I've not met a contractor yet who thinks the mastic-type pointing guns are anything other than a waste of time.
Standard mortar does not flow, as would be necessary for that type of tool. The mortars that are used for gun-injection systems have special additives to kep them 'fluid' while being pumped. Sue @ Easipoint would be better able to explain, but a simple sand + cement mortar packed into a cartridge is more or less guaranteed to fail.
Posted: Mon Oct 24, 2005 9:08 am
by SUE @ EASIPOINT
Hi
Thanks for the reference Tony.
The number of times I've been told ' I've bought a gun like that, but they don't work!'.
Yes, you do need to buy a mortar that's designed to pump, but having done that you'll find it does make life a lot easier.
Anyone interested in supply can contact us to find their nearest stockist or buy direct.
Cheers
Sue
01257 224900