Is there a trick to stacking three or more layers, (not tiers) because I have tried two cakes, one with three layers and the other with four and both of them sagged more and more each hour. They looked great after I covered in buttercream, I chilled them in the frige for several hours, but after the fondant went they they began sagging and bulging. I put dowels in one thinking that might help, but it didn't. What am I doing wrong?

what is the filling? it might not be up to the job, or it might be too thick a layer.
what type of cake is it? i belive some, like angel food cake, can not support the weight of the fondant.
what is the height of the tier? if it is coming out high, like 6 inches, it might be you need proper supports, boards and dowels, inside.
xx

Also, are you piping a stiffened buttercream dam for your filling?

Both were an altered cake mix cake and I used buttercream for filling, with a stiff buttercream dam. On one cake the layers were about 1 and a half inches and the other maybe closer to 2". One cake was over six inches tall.

Both were an altered cake mix cake and I used buttercream for filling, with a stiff buttercream dam. On one cake the layers were about 1 and a half inches and the other maybe closer to 2". One cake was over six inches tall.

Both were an altered cake mix cake and I used buttercream for filling, with a stiff buttercream dam. On one cake the layers were about 1 and a half inches and the other maybe closer to 2". One cake was over six inches tall.

Both were an altered cake mix cake and I used buttercream for filling, with a stiff buttercream dam. On one cake the layers were about 1 and a half inches and the other maybe closer to 2". One cake was over six inches tall.

Sorry for repeats. My computer seemed to be frozen.

That is a pretty tall cake. Some decorators recommend supporting every 4".

Thanks for your help. So a cardboard circle every four inches?

cardboard and the support dowels.

I'll give it a try. Thanks again for your help.