Dry grouting cobbles/setts

[Mr Sandman]

Hi all,

I have just put down an 80sqm cobbled path and am looking into options to point/grout it. Wet grouting will take 2 workers 4 days they recon, and at

120£ per day, will be expensive. Have looked into geofix polymeric sand grouting, but I will need a box of the stuff for every sqm and @ £25 a box, will be also expensive. I am thinking about going with dry grouting, 1 cement to 3 sand mixed with mortar colorant to make it dark grey.

Looking at washing the cobbles down the day before grouting to get the cobble base moist, then the next day (if its dry) brushing in the dry mix, pushing it down firmly with my fingers. Should I be ok just to leave it at that with no more watering, i.e. will it go hard without spraying it with water? How long will the hardening take?

Cheers

Steve

[Bruce]

There will be some moisture in the sand. That might be enough to make the grout set but in any case, soon after grouting, I would go over it with a watering can with a fine head on it - not enough to flood it, but enough to percolate through the grout and moisten it. There would be no harm in doing this a second time about 1-2 hours later.

After 4 hours or so, there will have been an initial set, and I would then wet the setts with a hosepipe and use a stiff broom to clean any grout off the setts, as there will always be some.

Personally, I would be tempted to include some latex admixture in the grout mix which would tend to improve its durability, but I would welcome other opinions, contrary or otherwise!

[Andy Hall]

I looked at these options for a drive and paths of handmade bricks, cobbles and setts.

For most of the area (several hundred square metres) I elected to use dry coloured sand and not to attempt to point or grout with mortar at all. This was applied with the bricks perfectly dry and the sand perfectly dry and brushing it into the gaps in multiple directions. It filled the gaps, compacted and does not wash out to any noticable degree.

There are two places where a different technique was needed. One was a single row of bricks laid lengthwise between the front of a garage and an Arco (strip) drain running along parallel to the door. The other was a row of bricks at the top of a section of sloping path. In both cases, there was a tendency for the sand to wash out in heavy rain. To address this, I mixed some of the sand at a rate of 5:1 with cement, and again making sure that it was *very* dry and that the bricks were *very* dry I brushed it into the gaps.

It wasn''t necessary to apply artificial water to this - it soaked it up from the ground below in a day or two. However, even with this degree of care, there was still a certain amount of cement on the surface. This was removed a couple of days later with brick acid, but it was a time consuming job.

I think that you would be making a rod for your back by attempting to point an area like this or indeed doing anything substantial with cement on wet surfaces or even dry ones.

[meow2222]

Sand alone is extremely easy, but in time you get weeds & moss.

NT

[The Medway Handyman]

Never done it myself, but I have seen Tommy Walsh use this on Ground Force several times :-) He used it on slabs, not cobbles though.

His method is to pick a dry warm day & use a watering can (no rose) to wet between the slabs. Then wait for the surface to dry & brush in dry mix which would soak up the water between the slabs. Very similar to your idea.

Extra watering no matter how careful you are will cause some motar splashing onto the surface.

[Andy Hall]

You do with a mortar fill as well, if you allow weeds to grow through, plus it may well crack it.

It's moderately easy to spray and destroy any weeds.

[Andy Hall]

Very different. If slabs are involved, the objective is normally to make a perfectly filled surface. With cobbles, mortar joints, unless really toned down in colour tend to dominate and ruin the appearance, especially if the joints are wide.

I wouldn't set much store by anything that Tommy Walsh does on TV shows.

Pavingexpert is a rather more reliable source.

[slider]

I think all the pro's will probably say......

stay clear of dry pointing. For a proper finish wet point.

[Andy Hall]

.. or don't use cement at all with blocks, pavers, setts and cobbles.

[The Natural Philosopher]

I mostly agree. Use dry mix, and if it has cement in it, it will set. Cement absorbs atmospheric moisture and ets off in a few weeks as anyone who has left an open bag of cement in a garage will testify.

Once it has more or less set, use a stiff broom and brick acid and a hose to wash off the surplus.

[Pete C]

[Pete C]

Hi,

What about lime insead of cement mortar? Would allow a little movement instead of cracking.

Might not be durable enough tho.

cheers, Pete.