failing at paving slab gap grouting

[steveo3002]

need a bit of help here

ive tried to re grout our paving slabs and its all falling out again after a few weeks

ive varied the mix between 3:1 and 4:1 by volume , and used sharp and builders sand (2 seperate attempts)

first try i made the mix dry , then swept into the gaps and watering canned it

second try i mixed it a bit dry and troweled it in

cant really see what im doing wrong , im usualy ok at that kind of thing

[R500POP]

I usually mix it dry, brush it in, then damp down with a fuine mist from a plant sprayer.

[98elise]

Are the slabs moving?

[steveo3002]

R500POP said:

I usually mix it dry, brush it in, then damp down with a fuine mist from a plant sprayer.

what mix ? packed in or just swept in loose ?

[R500POP]

steveo3002 said:

what mix ? packed in or just swept in loose ?

I just buy the pre-mixed morter from B&Q, it's really fine & not had a proble in the 10years out patio has been down.

[steveo3002]

98elise said:

Are the slabs moving?

not that im aware , its just falling away the mix is crumbly

[mattdaniels]

Buy the pre-mixed patio grout from Wickes.

Remove all of the old stuff.

Get a watering can and pour water in to all the channels to give them a good soaking. Make sure the sides of the slabs get a soaking and keep as much water off the top faces of the slabs as you can.

Leave it about an hour, then brush the dry mix in.

The mix will absorb the water and go off and then as long as you did not get any water on the slab faces you can brush off the excess.

That's Tommy Walshes method. I saw it on the telly the other day so it must work.

[toast boy]

You can get epoxy resin grout that works really well but is quite expensive I think. Just brush in and tamp down with a jointer, repeat a couple of times and it goes off in a day or so. Really easy and very effective.

[Deva Link]

mattdaniels said:

Get a watering can and pour water in to all the channels to give them a good soaking. Make sure the sides of the slabs get a soaking and keep as much water off the top faces of the slabs as you can.

I'm bemused by how it would be possible to do that and keep the top surface dry?

[wolf1]

I just swept post crete (the fast setting stuff) between the slabs and sprinkled it with the hose. Ten minutes later all set and hasn't failed since.

[Firefoot]

Deva Link said:

I'm bemused by how it would be possible to do that and keep the top surface dry?

I'm guessing you take the rose off and use the spout to direct the water along the channels.

[Deva Link]

Firefoot said:

Deva Link said:

I'm bemused by how it would be possible to do that and keep the top surface dry?

I'm guessing you take the rose off and use the spout to direct the water along the channels.

While giving the sides a good soaking?

I guess it would be feasible in warm weather as the top would dry off quickly.

[dickymint]

I've used all of the above methods. I've found the best way that lasts longest is..........

1) 4 sand, 1 cement, 1/3 lime.
2) mix dry thouroughly (this stops the cement "beading").
3) Shot of concentrated "Feb" plasticiser"
4) Use a hose with a fine spray and add water in stages.
5) Let it all mix for at least 20 minutes.
6) Get it to a putty like consistency.

Now use a pointing trowel and tamp the mix into the gaps using the edge of the trowel. Make sure the gaps are full and compacted down well (most important bit). Now you need to "strike" the mortar before it dries too much (this is weather dependant and comes with experience). You can use a striking bar but I prefer to use my pointing trowel (depends what finish you want). Lastly lightly brush the gaps with something like a 3" soft paintbrush.

Last month I re-pointed an old brick wall about 20 metres long and 2 metres high. My mate bought a gun similar to this............

http://pointmaster.co.uk/uvideo.html

Fantastic bit of kit and will be trying it on my next patio.

[beedj]

Best tool by far for pointing between slabs is a piece of regular copper pipe bent into a "lazy" Z shape so you have a handle - 15mm or 22mm to suit gap between slabs . If the mortar is a fairly dry mix (but with some water), you can push the mix down into the gaps quite firmly with the pipe-tool, then brush away any 'overflow' forced out - brush and pan works fine. If the mix is dry enough the overflow will not stain the slabs

[mattdaniels]

Firefoot said:

I'm guessing you take the rose off and use the spout to direct the water along the channels.

Ding, sorry thought that was obvious.

[driverrob]

I've suffered the same problem repeatedly. It's a very large patio and not laid on solid concrete. The slabs move. So I've given up. I did find the bags of pre-mixed mortar were hardly mixed at all and gave very poor results unless I spent ages stirring the powder first. The smaller areas I've laid myself on concrete have kept their mortar well.

Not of any use to you but interesting: Spent a few nights in Aqaba some years ago in mid-summer. At about 7:30 a.m. we saw from our hotel window a bunch of workmen just finishing laying the slabs for a pedestrian area in the shopping centre. Temperature then about 30C.
With hardly a pause they poured a load of mortar slurry over the slabs and brushed it into the gaps. Within minutes they were brushing the powder-dry mortar off the slab surfaces. Within an hour (about 35C by then) the area was in full use by the public.

Different world.