Hi all, I would appreciate any advice that is out there with regard to this.
I have taken the advice of this awesome website and decided to use a bond bridge (SBR & Cement slurry) to lay my Brazilian Slate tiles in an attempt to get them to "bond". My question is (which isn't clear form the website), after applying the bond bridge slurry to the back of the tiles, do you let the bond bridge dry or go tacky before laying on the bed or can you lay them straight away.
Hey! I resemble that incineration! The Bond Bridge page states....
...check the paving for any spills or splashes and clean them off immediately before moving on to the next unit. It can be scary to witness just how bloody quick this stuff can set, especially in summer!
...if that doesn't indicate that the paving has to be laid while the jollop is still wet and drippy, I don't know what does!
I just wondered if you could coat a few slabs with the jollop before it dries in the bucket and then lay them when it had dried on the back of the slab. This would minimise the chances of contaminating the front of the slab with wet jollop from gloves etc
If you daub a handful of flags at a time, how do you store them while they're waiting to be laid? On their backs? On edge? The SBR *will* dribble and you risk contaminating the face.
I've watched this being done hundreds of times and the method used by almost everyone (there was one dickead exception!) is to daub and get the flag laid one at a time, so there's less chance for the slurry to balls things up.
Point taken, I have already laid a few using the individual coating / laying method.
How long before the bond should have taken. I laid a few on monday using the following method and I tentively tried to lift one yesterday and it came straight up :-
Bedding Mix - 6 : 1 Sharp Sand / Cement with a dribble of plasticiser - relatively wet mix
Bond Bridge - Cementone SBR mixed with Cement to a slurry
Method :
Wash down back of slate with clean water, leave to dry
Dampen concrete sub-base and Prepare bed for laying
Coat back of dry slate with SBR Slurry
Lay & Level
Clean top of slate with clean cold water & sponge
The one I lifted had got a full bed (100% solid, no voids) but I am wondering if I should have left it longer before trying it. I am very aprehensive about laying anymore at the minute with the fear of the same happening.
What I am doing wrong or should I just leave it longer to bond before trying it.
The only other option I have thought of is laying a dry Sharp Sand / Cement screed and then using exterior tile adhesive to bond the slate to the screed. Is this an option (obviously increase in cost associated with this method)
I would say your bedding mix is not wet enough
I have said it before but I add 100ml to every gauge of bedding mortar and that sticks like the proverbial to a blanket
also the slate should be wet as well
I can say 100% if it was wet enough you wouldnt be lifting it
LLL
what do you mean you add 100ml to every gauge of bedding mortar ? Are you adding SBR to the bedding mix ?
I was under the impression this made the bedding mortar dry too quickly.
I will be laying more slates this weekend so will make sure bedding mix is a bit wetter and slate is wet when I apply the SBR / Cement slurry and see how that goes.
Thanks for all the replies and keep up the good work. I have found this site and forum invaluable over the years
One of the problems with SBR is that there is no standard 'strength' and some brands give themselves a bit of a price advantage by diluting super-strong SBR down to super-cheap SBR. This explains why some serious heavyweight commercial brands can be close to 20 quid per litre while certain DIY sheds can do 5 litres for a tenner.
Still, even the weaker stuff should have bonded after 24 hours.
Where is it coming apart: is the slate lifting clean from the bed, or is it bringing part of the bedding with it? If the SBR is effective, it will bring bedding with it, but if it's separating between slate and bed, then the slurry is failing for some reason.
The SBR I used was Cementone from the local Builders Merchant (£17 for 5 litres). I assume this is one of the better brands but I may be wrong.
I would say the SBR / Cement slurry I made was a bit more like a paste but brushed on and spread okay with a fence brush. Admittedly, it was getting a little bit stiff when I got round to laying the last couple of slates of the session but it still spread to all corners of the slate.
The slate I lifted came completely off with no bedding mortar stuck to the slate at all (this was one of the last ones I laid). I would say it was 12 hours between laying and me lifting it. I have not tried to lift anymore yet as thought I might leave them a bit longer to "bond". I will try lifting the 1st ones I laid tonight (when the slurry was more of a slurry than a paste) to see if they are any different.
Should the slate be wet when applying the slurry as LLL suggests ? (LLL, I am not questioning your sound knowledge, just that there is conflicting information out there). I read somewhere that if the slate is wet, the pores in the slate are filled with water preventing the slurry penetrating into the pores (this they say is why you soak slate when pointing to avoid staining).
I am by no means an expert on paving which is why I am on this forum. I just want my slates to stay put (especially on the steps).
Try this stuff Priming slurry.
It impressed me, goes further and is usable for longer than it states.
I haven't used it on slate but wouldn't hesitate to try it.
Test your sbr slurry, paint some on a slab let harden then see if it will scrape off. If it does I think I would try a different sbr.
You could also be over compacting the bedding. A few little voids in the top surface of the bedding won't hurt. Raking a little of the bed out gives the mix somewhere to spread as you compact the slab.
I'm a bit of a DIYer but have laid patios before but I realised reading this site that maybe I made a few schoolboy errors.
So I'm after some advice on mortar beds:
I'm about to lay natural slate tiles (20mm thick, 30 sqM patio, four different size slabs/tiles 900x600, 600x600, 600x300, 300x300 etc)
I have around 150mm of compacted crusher run down. Nice and flat and solid.
My questions are about the bedding layer/mortar bed etc:
Here's what I was thinking:
8 parts sharp sand, 1 part cement - 40mm thick and Moist (as the site says moist is easier sometimes for the likes of me).
Also use a 'bridge bond' as you describe in this post.
Now, reading on here I've started to worry that my 8:1 thinking might be wrong. I read I should use a 'class IV' mortar but started getting confused with the ratios and the mention of lime and plasticiser etc etc.
Can someone explain what the difference is and tell me if what I was thinking would work?
8:1 is fine for a patio - it's roughly equivalent to a class IV mortar.
Don't worry about lime - the justification for using it with paving is complex and probably applies to less than 0.1% of all the paving laid in this country. Just use a plasticiser and/or more of the SBR in your bedding mix, and make sure you have a good slurry on the underside of the slate, as it is notorious for not "sticking".
