The Brew Cabin

How best to grout between textured slabs & 50mmsq granite setts without staining .
I want to add black colorant to darken cement & this will
only stain worse .
I tried some wet, but impossible not to get over setts& slabs . If dry - is it completely dry - do you 'strike ' joints later to smooth, or just brush in .

Textured flags, whether they're shot-blasted or bush-hammered, are a total bloody nightmare to point up without staining, and if you're using a black or a dark mortar (not "cement", note, but MORTAR!!!) it seems to be even harder to get a neat finish.

As you've experienced, if you use a wet mortar it slops everywhere and stains, but if you use a dry 'brush-in' mix, it doesn't set as well as it should to give a good joint. There's an old trick of brushing in dry and then wetting the lot via a fine rose affixed to a watering can, but this still splashes some of the mortar onto the surface of the paving. Further, a dry mix doesn't 'colour' properly. The cement dyes used to make coloured mortars rely on water to disperse the powder and activate their colouring power, so you don't get a good depth of colour with a dry mix.

One method we've used successfully in such situations is to use a semi-dry mix, adding just enough water to bind the mortar and bring out the colour. It's damned hard work mixing a mortar in this way - you have to keep the water content to an absolute minimum, which means it's very, very stiff, but you also have to mix thoroughly to prevent any 'streaking' of the dye within the mortar. Once mixed, the semi-dry mortar can be fed into the joints from the blade of a brick trowel and pressed in with a pointing bar. If the mix is just damp, it tends not to stain the surface of the paving if accidentally spilled, but it gives a good, hard joint of full colour. Any accidental spillage should be sponged down asap.

Other methods you might use include...

- masking: you can use masking tape to protect the surface immediately adjacent to the joint

- retarder chemicals: Grace Pieri have an interesting substance by the oh-so-catchy name of NMP01 that they claim can be painted onto the surface of paving to protect it from mortar stains during pointing. I'm not sure how readily available it is for DIYers or what it's cost might be, but it's certainly made me sit up and pay attention.

- wet grout: this method is illustrated on the website, and it works quite well with 'awkward' pavings such as you have, as long as you are absolutely, totally, 100% methodical in washing off all of the mortar slurry. Could be a good method to combine with the retarder idea mentioned above.

- polymeric compounds: there's a good few of these on the market, and they are becoming more readily available in a range of colours, although I've still to see a genuinely dark-grey/charcoal/black. All of the so-called dark colours I've seen have actually been medium grey at best. Some are dry-brushed in and then cure by exposure to the atmosphere, while others are mixed to a wet consistency and poured into the joints from a watering-can or can be pumped in via specialist mortar guns.

I can't tell you which would be best for your project. You need to think about the skill levels available, the size of the job, the budget, how much time you can afford to spend, the end use....and then decide which is best suited to the job in hand. If it were me, the very stiff mortar would be my choice, but then, I've been pointing flags since I was three years old and have almost got the hang of it now. :)

Thanks for this . Masking tape & dry mix looks good . The area was around a raised bed and used paving slabs with 4 setts between each . I like the look of the setts and aim to do adjoing patio area . Leads to next Q.

With patio, I want to lay on 'screed' with 10:1 as your info shows this to be good . How best to incorporate setts into this . I was aiming to do a 1 or 2 deep rect band . The slabs are 40mm & setts 50 deep, but the setts are irregular - do I remove the 10:1 screed and bed the setts in strong mortar . I was hoping to use sand joints for slabs & dark mortar for setts .

If I do a rect of setts, is it better looking to cut the inner
slabs so that slab joints inner/outer line up , or work from each side & cut in central ones ?

I seen from other links, folk complaining about Marsalls
products being plain, looking at their slabs, my local firm Tobermore do a far better range of textured stuff - they look like textured stone not textured cement .
Pity that they are hard to deal with - no stock, made to order, no guarantee of delivery date, leaving BM & B&Q offering finest Marsalls stuff.

Cheers - Dermot

As there's only 10mm diff between the slabs and the setts, I'd probably leave the 10:1 screeded bed in place and just loosen it with a torwel as I came to lay the setts, and remove some of it to accommodate the extra depth, and then tap down the setts so they're flush with the slabs.

I'm not sure which would be the best waty to work with your sett rectangles. Ideally, you'd use full setts and full flags and avoid all the cutting, but it's not always possible. In your situation, I'd do a dry test panel first to see which looked best.

Tobermore only serve Norn Iron, don't they? I've never seen their products on this side of the water. I think they use a shot-blast texturing process which is essentially the same as Marshalls (and lots of other manufacturers) but the big diff is the starting material. The aggs and dyes that Tobermore use are different from those used by Marshalls, which is why the end product looks so different.

I'm surprised to hear you've not much praise for the Tobermore customer services. I was talking with a contractor from Derry last time I was over, and he said they were a great firm to deal with. Maybe they treat private customers less effectively than their trade regulars.