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I just installed some 12" x 24" large format tiles in my laundry room using Flexbond mortar over concrete that was machined with a diamond cup disk. Its been ~32 hours since I finished the main portion but its clear that that the mortar is still curing. It can take foot traffic at this point but I really need to get my washer/dryer back in there ASAP because I literally have no clean clothes ;)

How long should I wait before hauling these two beasts back in there?

My washer is probably ~300 - 350 lbs (it has huge concrete blocks in it for counter balance) and the dryer is a good ~170 lbs.

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    That looks really nice. Great job! – Shane Wealti Jul 14 '14 at 17:49
  • Check the recommended cure time on the mortar packaging and follow that. It varies depending on the type. I generally wait 36-48 hours to apply the grout afterward (I am cautious, that is far more time than is generally needed). – James Jul 14 '14 at 17:54
  • Better to give it time and make a trip to the laundromat than to ruin what looks like a nice tile job by being in a hurry. Nothing like a trip to the laundromat to make you more fully appreciate not having to go there all the time. I'd want to aim for a week's cure before putting in anything that heavy. – Ecnerwal Jul 15 '14 at 0:58
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It depends on the concrete permeability and the tile permeability (is it porcelain (essentially zero permeability) or a ceramic bisque (most non-porcelain tiles))?

A sealed concrete floor and a porcelain tile will greatly extend the cure cycle by limiting moisture migration.

It is for this reason that Schluter (a tile membrane manufacturer) specifies a non-modified (no latex added) thinset for its floor membranes and porcelain tiles together (on the tile side of the membrane). They make the same requirement on the floor side, if the floor is limited in permeability. Flexbond is VERY modified.

If sealed floor and porcelain, 48-72 hours is safe. The tiles will cure properly with EVEN compression (the weight of the washer), if spread over several tiles.

Would it be possible to temporarily put down several 1/2" ply feet, that span from front to back, under the washer/dryer feet?

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According to the documentation link for Flexbond that you provided - the cure time is 72 Hours. Me personally I am cautious an extra day will not hurt it.

You said that you machined the concrete with a diamond cup disc - does this mean you smoothed the surface or roughed it up - the instructions for your flexbond says a smooth concrete surface is more problematic and that you should mechanically abrade the surface (hopefully you rough ground and not polish ground) - see the technical document bonding to concrete surfaces - click the PLUS next to technical specs.

Cheaper to do it right the first time than to do it right the second time.

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next time, tec fast set mortar, can be waked on in 3 hours and grouted in 4. learning curve using it but well worth it. life exists in the places tile is put down; now i see why wood is so popular...down and done and it is everywhere. what kind of washer and dryer do you own? those weights are drastic.

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I concur with HerrBag and Ken.

Flexibond is an excellent product but it was overkill for this installation. It’s a modified thinset basically to give some flexibility when installing over an existing floor e.g. vinyl or wood where there may be a slight “flex” in the underlying floor.

Why do you think the mortar is still curing? Do you mean the grout is still curing? It shouldn’t take more than 72 hours tops, even with all the polymers in the mortar. Did you add Admix to the grout as well? That would increase cure time.

Your concrete substrate is great unless it’s smooth as Ken mentioned. What’s done is done. From here I would let it cure fully 72 hours before the heavy laundry machines.

Additionally, I think it would be wise to set the machines on exterior grade 3/4” plywood. You could use one sheet for both machines or cut to dimensions at the base of each machines + 1/2” on each side for a less detectable finish.

Reasoning here is that because of all the mentioned factors re: tile material, modified mortar, possibly smooth substrate, the fairly intense and constant vibration of the machines could, over time, loosen the mortar/tile bond and dislodge or break the tile. Stabilizing the machine on the plywood would reduce the stress on the bond.

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