How important is it to prime porcelain tiles for patio?

[Fez111]

Hi All, Seeking a sense check/ advice please. Laying down 30m2 of 20mm porcelain tiles for garden patio, and most googling seems to suggest using slurry primer or equivalent on the back.

My builder is suggesting they never use this or any other primer - they lay straight on to the mortar bed/ sand cement mix (they’ve already compressed mot underneath). Now typically I would happily question trades if something seemed off, but this builder has done work for me for over 15 years - lofts, extensions, full refurbs across several houses and they all look good and standing strong after all these years, and I do trust him. So two questions really -

1. How bad is it if you don’t use the primer?
2. Would you still persist?

Any other advice? Thanks in advance.

 

[Mr Chibs]

Personally, I'd prime, you stand a greater risk of the tiles coming loose when/if water can get underneath them.

When I have lifted 'primed' tiles/slabs, it usually lifts the sub base (lime) up with the tile. Un primed tiles/slabs can usually be separated.

I like to use a slurry of cement and SBR mixed to a double cream like consistency, either roller or trowel on, just before laying.

If there is no primer, they may look great for now, but they may work loose with time, when the builder has gone.

 

[Nintendofan]

I'd go with what the manufacturer of said porcelain recommends in their installation instructions.