The Brew Cabin

Morning Tony,

Spent the weekend laying a terrace of Stonemarket Millstone honey-gold flags, following your excellent guidelines for a semi-dry bedding mix. Intending to point them some time this week.

Horror of horrors..... after finishing the laying on Sunday evening and when, in a tired but self-congratulatory mood, I reread your advice, I realised I'd not buttered the bl***y things with wet mortar. In fact, not a drop of water had been used throughout the entire operation! The word "berk" springs to mind, I know!

I think I will weep real salt tears if I have to take them all up again, so I now have to ask your advice on pointing.

Had originally intended to use a 4:1 dry mix, brushed into the joints.

Question: If I brush out/vacuum as much as possible of the 10:1 weak mix from between the joints, can I still brush in a 4:1 dry mix? Was intending to use a half and half mixture of sharp and building sand, plus cement The terrace only gets very light foot traffic crossing it.

Question: If so, will this avoid the grey colour that many mortars seem to take on? I'm in East Sussex, and the building sand is quite red. Or, can I add a dye in powder form to the dry mix and expect it to do the business? SWMBO doesn't want a very dark mortar, more of a light brown/gold.

Thanks for all the fine advice on your site. Pity that some of us amateurs still cock it up!

Regards

George

Hi George,

Fear not: it's not the end of the world if you omit the buttering. That method works best if you're going to be filling the joints immediately after laying, but, in cases such as yours where there's a delay between laying and pointing, then it's not critical.

And the idea of vacuuming out the bit of loose bedding in the joints is a waste of time. Ignore it - it's doing no real harm. However, dry jointing of this type of flag is rarely 100% successful unless it's done on top of still-plastic buttering mortar. It tends not to 'set' properly, remaining crumbly, and it doesn't bond to the edges of the flags, so it cracks and disintegrates and comes loose over a year or so, which is why it's not one of my preferred methods.

So, how do you deal with it? Well, the old trick of dry-grouting then sprinkling on water via a fine rose on a watering can improves the situation, but we find that it also tends to splash dry mortar onto the surface of the flags, where it's immediately wetted and will stain, unless it's washed off straight away.

This method can work, but, as I say, you need to pay attention to any splashing and, very important, you must tool the joints, pressing the damped mortar into the joints and polishing it to a smooth finish. The work is best carried out in the late afternoon or early evening of a dry day when there is no chance of overnight frost. This allows the mortar to cure overnight at a steady pace, rather than be scorched dry by the heat of the day.

Other options would be to do a wet-grout, but this can be hard, if not impossible, to clean from the delicately textured surface of the riven replicas such as Millstone, or, and I know you don't want to hear this, the best solution of all is traditional hand pointing. Slow, laborious, back-breaking, but by far the best.

If you don't mind spending a few bob, then you could opt to use a polymeric sand, such as GeoFix, or even one of the pourable jointing compounds, such as Ultracrete Flowpoint from Instarmac, but this is probably a bit much for a domestic patio.

Your next question refers to colour. All you can do is experiment. Mix your sands and cement and see what colours you achieve. Whether you use grit sand or building sand doesn't really matter with these wider joints, but the end colour of the mortar is largely determined by the colour of the sands, so, if you have a buff or yellowish grit sand, mixing that with a red-building sand may give the shade your beloved requires. If not, then it's a matter of adding a dye, a brown or a marigold should give the sort of tone you;re after, but remember, the colour of a wet, plastic mortar is not the same as the colour of a cured mortar. Do a few trial mixes to determine exactly the shade you want before starting on the pointing.

It's worth noting that, if you choose to use the dry jointing method, then the colour of a dye is much harder to implement, as it needs to be forcibly mixed in the presence of water, to properly colour the mortar. This doesn't happen with the dry jointing method, and what you end up with is a streaked or spotty mortar. If a coloured joint is required, then you really do need to use a wet mortar, but if a simple jointing procedure is more important, forget the dye.

Thanks, Tony, for your reassuuring advice. Very relieved to know I haven't got to take them all up again.

Have decided on your advice to abandon ideas of dyeing mortar and will instead experiment with different 1:4 cement & building/sharp sand combinations to get reasonable colour. I'm afraid that it will have to be dry brushed in (once the rain stops for a few days) because I know my own limitations as far as wet pointing goes. Those Stonemarket flags are just too expensive for me to afford to ruin them all in a day with a small pointy trowel!

Once again, thanks for your response.

Regards

George

You could do what Scott up the lane did, and use masking tape on all the edges. I think he spent more on bloody masking tape than he did on sand and cement, but it looks good! ;)

Good idea, and I like the notion of bringing the methods of one trade (painting and decorating) to the materials of another (paving and hard-landscaping). Shows adaptability and forward thinking. Now, if I can just find someone to replace my bitmac drive with a nice bit of laminate flooring, put in a dado rail and skirting along the garden wall, and carpet the garage, I'll have a very happy wife indeed . . . . . . . .

If you like the idea of swapping skills between the trades, you should take on a certain employee we once had from Wigan, who took home a load of 3x2 'council' flags we'd taken up from a streetworks project in Aspull and used them to pave the floor of his bedroom - upstairs in a 2-Up-2-Down! :o