We installed new stone tile in our second-floor bathroom. After reinstalling the toilet, should it be sealed with silicone caulk at the base or left as is? I suspect a ceiling leak on the first floor might be from this toilet when it overflows, so am inclined to seal at the base.

If the toilet sets level and doesn't rock at all, I prefer not to caulk the base. If you do caulk the base I suggest leaving the back portion of the bowl uncaulked so that if the wax seal ever starts to leak you will see the water comeing out from under the bowl. Caulking toilet bowl to floor makes for a messy job if the need arises to remove the toilet for wax replacement or toilet replacement. There are many opinoins on this, but I usually only cualk the base of the toilet if the customer insists upon it, or if it is necesarry due to unlevel floor etc.