The Brew Cabin

Help!

I recently attempted to lay my first ever patio, out of Bowland riven mock stone flags, mainly 500 x 250 x 45

I dug out an old, compacted lawn and, as advised by the builder's merchants, spread out some concreting sand into which I raked some cement and roughly leveled it.

I then had a first attempt at mixing mortar and laying the first flag. Disaster! Despite what I had seen on the telly, my mortar mix seemed too thick and dry to work with. After several unsuccessful attempts, I gave up and scraped off the mortar from the sand.

I then discovered articles on your web site that suggested a 10/1 mix for bedding instead of mortar - obviously similar to what I had been advised to lay for the base before mortaring.

I now wish to use your 10/1 mix method for bedding, but have several questions:

1) It has rained since weekend, and I now have a patio bed full of a concreting sand/cement mixture, some areas are mainly sandy and therefore soft, some hard where it's mainly cement, and bits in between. Will I need to take this up and start again, or can I put your 10/1 mix on top (I'm worried about settlement in the semi soft areas)?

2) I'm confused about the type of sand to use. The builder's merchant where I got the stone spoke of grit sand, but delivered bags marked concreting sand. The merchant where I now wish to buy the remaining sand I need is talking about sharp sand as they do not stock grit sand or concreting sand! Does it matter which of these I use for the 10/1 mix I wish to bed the flags on?

3)Final question (sorry). What is the best method for pointing on the 10/1 mix. I bought some Geofix to brush in dry, but that was when I was going to mortar and attempt to 'butter' the flags?

1 - I'd throw out any really hard bits, dampen the rest lightly with a hose, then sprinkle cement over the rest, rake it through and run the plate compactor over the lot. If you don't have a plate compactor, then stamping on it so that you compact the entire area will be almost as good.

Once that's done, you can use 20-25mm of the 10:1 mix for bedding.


2 - Oh the joys of terminology in the building trade!! To all intents and purposes, grit sand is concreting sand is sharp sand. There are minor differences between them, but, for the type of project you're undertaking, those differences are totally irrelevant and you can use grit sand OR concreting sand OR sharp sand, or even a mix of all three. What you DON'T want to use is building sand, which may be known as soft sand or plastering sand. Confusing, innit?


3 - You could use Geo-Fix but I still have reservations about its use on the wide joints you'll end up with using the Bowland flags. I still firmly believe that you can't beat a mortar joint with that type of flag. Butter the receiving edges with a Class II mortar as you lay, point up the joint asap to keep out other crap, and then, after an hour or so, strike the joints to finish them. Leave them for about 4 hours and then you can brush off. :)

There's a new page dealing with pointing 'in production'. I took the photies a couple of weeks back, and drafted the text over the last few evenings, so it's just a matter of coding it all into html now, and slotting it in to the rest of the site.

Thanks Tony.

When you say 'Butter the receiving edges with a Class II mortar as you lay', do you mean use the 10:1 sand/cement mix to butter the edges, or lay the flags on a 10:1 sand/cement mix and then use some 3:1 mixed mortar to butter the edges?

The Bowland stones seem to be designed to touch at the bottom while leaving a gap for poiting at the top. If I butter the edges, do I still force them to touch at the bottom, which will presumably force the buttered part of the bedding mix upwards?

Finally, does using the 10:1 mix to lay the flags mean I can stand on or use the patio immediately, or should I wait a couple of days until the cement has gone off?

This is a brilliant web site by the way.

Keep up the good work.

Use a Class II mortar for buttering and pointing (that's roughly a 3:1 mix), and use the 10:1 mix of grit sand and cement for bedding.

Bowland are not the only manufacturers to have these wierd moulds that make the flags have splayed-outwards edges, contrary to natural stone, which always has the edges splayed inwards. However, you should endeavour to keep the flags far enough apart to ensure they are not quite touching, but that the top of the joint is not excessively wide.

Using a 10:1 semi-dry mix means you can walk on the patio a mere 24 hours later - in fact, if you're careful, and the flags are securely bedded with no movement or rocking, you can walk on it immediately. At this time of year, the bedding mix will be reasonably 'hard' after about 6 hours, but, if you're pointing as you proceed, best to leave them for 24 hours, just to be sure. :)

As mentioned in my reply to Mick's circle problem post, the new page on pointing stone flags has now been uploaded and you might find it to be a useful read.

Tony,

Thanks. The patio is down (at last!).

The pointing was a lot more difficult than I thought it would be from seeing people do it. Maybe it comes with practice?

Anyway, I need further adivice. I have laid some 500x500 riven flags as a path near the patio. I laid them on a 10:1 mix, but decided to try and point them using the dry grouting method as a 3:1 mix. I decided not to use a Class 2 mortar to butter, but simply brushed the dry mix into the gaps, wet it with a fine spray of water and covered it so it could dry out slowly. Problem is, I forgot to strike the joints with a trowel.

It's been a couple of days now, and the mortar seems to have loose sandy grains on top and is not fully hard. Is it a write off, or am I being impatient, as I was expecting ther mortar to have gone rock hard by now.

Cheers.

You're right: real skill at pointing does come with practice. My Dad's had me doing it since I was 3 years old, as he hates doing it, and has no qualms about using child labour to save him the trouble! I'm getting to be quite good at it now! ;)

They dry-grout method never gives a really solid joint unless it is brushed into freshly-buttered joints and tooled to a firm finish, but I wouldn't worry too much about it just yet. The "mortar" is not going to get noticeably harder (it does, actually, but you'd need a laboratory full of equipment to prove it) but it may well be hard enough for your purposes. After all, it's only a way of filling the gaps between the flags, so, if it's hard enough to stay put and resist colonisation by weeds, it'll do, but if you find it starts flicking out, then a re-point may be necessary.

Take a look at the relatively new page on pointing. The method shown there works really well (if the weather's right) and isn't much more difficult than dry-grouting.