you have to ask the mattress manufacture for guidelines, as well as re warranty stipulations, i.e. you may lose your warranty rights if you don't provide a certain foundtion to the mattress. In general, though, innerspring mattresses hold up better without a foundation then do foam mattresses.

Bed frame designers want you to think that wood slats will properly support your mattress. The truth is the gaps between slats can cause your mattress to wear out faster. Best thing you can do is place a sheet of 1/2" plywood over the slats. This will help your mattress in the long run.

Plywood doesn't allow your mattress to breath and releases chemical wood preservatives. CCA Choromated Copper Arsenate pesticides. The more slats the better, the wider the better. Mattresses need to breath so I recommend slats that are between 1 - 3 inches apart 5 /12" hardwoods like maple are best, bevel the edges.

We make our own custom platform beds here in the USA, the strongest in the nation. It will hold any mattress of any type.

http://www.epa.gov/oppad001/reregistration/cca/

It definitely depends on how many slats you have on your platform bed. at my company, Yankee Mattress, we sell platform beds that have 5 or 6 slats in a queen size. also. a center support leg that goes to the floor is needed as well. If the bed has these specifications then we uphold our full warranty on a mattress that is put directly on the slats with no boxspring. Definitely check how many slats you have on your bed, and also check with the retailer your purchasing the mattress from to see if they stand by the warranty in this case.