Cementing? between the flag stones

[Jody]

I'm helping out at a country estate this month and one of the more mundane tasks has been to pressure wash all the flagstones.
The cement / grout ? is in a right state, much of it 'popped' out as soon as the lance went near it !

I'm guessing I can make up a mortar / cement mix and push it between the stones to hold everything together tight.

Q1 - Is it really that straightforward
Q2 - What ratios should I be using in my mix
Q3 - The water here is VERY limestone-y, do I need to consider that

HTH

[weeksy]

Usually quite a dry mix rather than a wet one i believe.

[cheb]

Isn't it usually dry sand brushed in, left, and then repeated as necessary?

[weeksy]

Isn't it usually dry sand brushed in, left, and then repeated as necessary?

My guy did it with some cement in there, same as for setting the flags. But still quite dry.

[Le_Fromage_Grande]

Dry mix and sweep it in with a soft brush, probably a 50:50 mix, but check with local builders merchant

[maccecht]

Things to consider. How wide are the joints? What colour are the flag stones?
Wide joints ideally need grouting with a semi stiff mortar and a jointing tool. Thin joints you can get paving sand and just sweep it in flags need to be bone dry though. If the joints are somewhere in between do a 5_1 silver sand cement mix dry sweep it in and let natural moisture do the rest. If the flags are light coloured make sure you clean up or the cement will stain the flags if dry jointing.

[Cousin Jack]

Isn't it usually dry sand brushed in, left, and then repeated as necessary?

Resin bonded sand is good. Sets reasonably firm.

[ZRX61]

Isn't it usually dry sand brushed in, left, and then repeated as necessary?

Resin bonded sand is good. Sets reasonably firm.

Is that the stuff called polymeric sand?

[Cousin Jack]

Isn't it usually dry sand brushed in, left, and then repeated as necessary?

Resin bonded sand is good. Sets reasonably firm.

Is that the stuff called polymeric sand?

Never heard that term, but it sounds as though it might fit. Sand with some sort of polymer to bind it.

[maccecht]

Resin sand is ok in narrow joints not so good on wide joints not to mention expensive

[Jody]

Bit more information for you.....

Flagstones are mainly red, but there's some grey ones in the courtyard and the ones by the tennis courts are all grey



The gaps between range from 5mm to 25mm

Someone has previously brushed course sand into the gaps, this flies out as soon as the pressure washer looks at it.

[maccecht]

Bit more information for you.....

Flagstones are mainly red, but there's some grey ones in the courtyard and the ones by the tennis courts are all grey



The gaps between range from 5mm to 25mm

Someone has previously brushed course sand into the gaps, this flies out as soon as the pressure washer looks at it.

Paving sand 5-1 sand cement dry mixed just brush it in make sure the flags are bone dry though moisture will do the rest

[formula400]

Bit more information for you.....

Flagstones are mainly red, but there's some grey ones in the courtyard and the ones by the tennis courts are all grey



The gaps between range from 5mm to 25mm

Someone has previously brushed course sand into the gaps, this flies out as soon as the pressure washer looks at it.

Paving sand 5-1 sand cement dry mixed just brush it in make sure the flags are bone dry though moisture will do the rest

Is that so it does not stick to the top of the flagstones?

[Silly Car]

Is that so it does not stick to the top of the flagstones?

Yep, nice dry mix on dry flagstone won’t stick to or stain the surface, the mix will draw moisture from below / sides and set. In the height of summer, you can lightly spray over with water to speed up the process.

Alternatively, damp mix (so it clumps together in a clenched fist), and down on your hands and knees with a pointing iron to work into joints.