How do we install tile over an aluminum substrate?


We were recently contacted by a general contractor asking us to install some quarry tile in a walk in 5x7 freezer and a 4x5 walk in cooler.

We were told that there was a steel diamond plate/tread floor panels that were able to be removed in which we would find concrete under the refrigerator walk in and plywood under the freezer unit. Our plan was to install. Schluter ditra and set the tile over that.

We were able to remove the existing plate on the refrigerator section, but we learned that the freezer unit was glued down. Our next plan was to prime over the steel plate and then use an approved superflex tec product to set the tile.

Once we removed the refrigerator plate we found that the construction was not steel, but actually aluminum. We were unable to prim over the aluminum as it would just bead up.

Do you know if there is any product or material that would bond over this aluminum plate. As we stand, our only option is to tile over as we are unable to remove the aluminum plate.

Thank you in advance for any time or advice you could provide.


ANSWER - In the past we would always use an ANSI A118.3 epoxy adhesive to bond to steel floors in freezers and elevators.  The steel would have to be scarified and cleaned first.  Then grout with an epoxy grout; either an ANSI A118.3 epoxy grout or a more chemical resistant ANSI A118.5 epoxy grout.

Not knowing how sturdy the aluminum substrate is, you need to verify it doesn't have excessive deflection.

The best approach to install tile over it would be to mechanically screw on self-furred metal lath with washers, so there is at least a 1/4" space below the metal lath.  Then use a polymer modified mortar bed mix, such as Laticrete 3701 in a bag where you just add water, and apply a mortar bed to a minimum of 3/4" thickness.  Make sure the mortar is forced into the metal lath to fill it incompletely so there are no voids.

If you need waterproofing then apply a liquid applied water proof membrane, and then adhere the quarry tile or porcelain tile to the membrane with a polymer modified thin-set mortar.  Make sure the tile is suitable for the intended use and that it is a slip resistant tile.  Be sure to install movement joints at the perimeters and transitions using backer foam or tape and filling with an ASTM C920 sealant such as a 100% silicone caulking sealant.

If the aluminum substrate was flat enough and without excessive deflection, you might be able to substitute the metal lath and mortar bed, but screwing in the backer board over the aluminium.

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