You've certainly taken remarkable pains with your installation. I would cover the cement board with something to cushion it against chips.

I have to say, though, that the problem with vibrations is not because the machines are connected to the structural members but because they *aren't* firmly enough attached to the stiffness of a house's structure. So your efforts to decouple it may be in the wrong direction.

In other words, washing machine vibrations that are transmitted to distal parts of the house are a symptom, not a cause. You may be able to contain any mis-vibration to the proximate area, but you will still have a "vibration problem", whether it's shaking your downstairs chandelier, or not.

A meticulous leveling job, and a stiffish floor firmly connected to the main structural components are what does the trick. Mieles, being true horizontal axis machines, are fairly stable all by themselves, provided they are perfectly level. Do not omit the leveling; even if your preparation contains the vibration away from other parts of the house, if the machine is vibrating in its little isolated world it will wear out early or fail if not correctly leveled and perfectly balanced, and then re-checked and adjusted occasionally, as it whirls on its merry way.

My older Mieles have lived on both cement and wood floors, and never vibrated inordinately. But I do take pains to get them set up correctly.

HTH

Molly~

Molly:

Thanks for your thoughts. You are saying that "the problem with vibrations is not because the machines are connected to the structural members but because they *aren't* firmly enough attached to the stiffness of a house's structure. So your efforts to decouple it may be in the wrong direction."

Perhaps I need to be clear what you mean by the "stiffness of a house's structure"? Say, I can frame two boxes - one will be very stiff, another one is more springy. How would the washer installation vary for either box, given that both are rated for the weight of the appliance?

A 360 lbs (full load) washer allows no other means for attaching it to the "stiffness of a house's structure" than it's own weight and a load-adequate and leveled installation surface. I think screwing legs to the floor is not a good idea. How else would you solidify this attaching to the "stiffness"?

For those who are not familiar with the de-coupling membrane [http://www.schluter.com/english/products/2002/sectionf/overview-f/section-f.html], its purpose is to isolate (rather than to transfer on) the structural movements above and below it. Such isolation, in case with the washer, may even minimisze a chance of a resonance* [http://dictionary.reference.com/search?q=resonance]. Molly, your comments are forcing me to go through due diligence. Always good! Happy New Year!

al

*I am not certain on that, but it seems plausible.

I've completed the project and tested.
@600 RPM it is stable, no movement, but there is definitely a vibration.
@900 RPM - as above with more vibration, but still no movement.
I have not tried @1,200 RPM.

Modifications:

Un-modified thinset for everything.
I left few screws used to bring down the periphery of cementous board. I hope that with time the cementous board will crumble around the screws and allow the movement (de-coupling membrane).

At this point I am not sure if I'd recommend this approach - I've done only four loads and have not tested @1,200 RPM.

al