Laying slate - adhesives and grouts

[theowls]

Hello All,

I am going to lay about 25sqm of slate (combination of 600x300, 600x600 and 600x900). The flags are 18-22mm thick with sawn edges. I intend to individually bed these using ~50mm wet mix mortar bed.

Question 1: Do I need any sort of adhesive to bond the slate to the mortar bed? If so, what do I need to use, what quantity and how is it applied?

Question 2: I have calculated that the joints will be 4/5mm wide. What is the best material/product to use for such widths? I don't particularly want to spend days grouting if there is an alternative solution out there that will produce the same results (looks and strength) as the traditional method.

Any advice will be much appreciated!

[DNgroundworks]

I have never laid slate paving but if a bond bridge is necassary i would use an SBR additive in the mortar or just paint it directley onto the back of the paving - i have found this to be quite effective in the past and as for the jointing maybe somthing like romex or GTFK again i have only limited experience with these jointing products but that is proberly the best solution.

Regards Daniel

[Tony McC]

We've been doing a number of trials with slate paving over the summer, trying various bedding methods, bedding materials and the presence or absence of a bond bridge. It's all in the process of being written up to appear on this website and that of the sponsoring company later in the autumn, but to summarise, the best results were obtained using a fairly stiff wet mortar of sharp sand and cement with a cement/SBR bond bridge.

Be *very* careful with the jollop, though. Wipe up even the slightest drip or drizzle *immediately* with a damp cloth. The proverbial on a blankets ahs nothing on that stuff once it's cured, which takes only 10-15 minutes at this time of year.

[theowls]

Thanks Daniel and Tony.

Tony - what's the cement:sbr ratio for the bond bridge?