One of the biggest things is footing of a stall.

I don't care if one chooses SAND, Stall pads, or Clay they ALL have up keep and will need to be put on a regular schedule for checking, securing, and replacing parts, components, or what ever.

First things first.
When choosing a place for a barn and your stalls do it right.
Make sure the barn or stalls are on a HIGHER ground that everything around it.
Even if floods are not an issue in your area there is ALWAYS a need for run off when a horse is being stalled for a long period of time.

SO make sure the building is on higher ground ...
AND next make sure you have plenty of drainage... you can not have too much drainage!
I have FOUR French drains in each of my two stalls.  TWO go out the back and TWO go out the sides of the stall.

What ever your choice of filler start with French drain pipes fill UP and OVER with nice size rocks and THEN place your choices of barrier cover!

A barrier cover is necessary to allow and protect your French drains.  If sand or clay fill your drains over time they no longer work so a good barrier is NECESSARY.

I did not use a barrier ONLY because I used pads. BUT even using pads a second layer of smaller rock is necessary THEN a good pounding of all materials, then I had laid one by two's and had pee gravel  in between them, then my perfectly places mats on top of all that. 
SO I have lots of drainage AND I simply keep my stalls DRY  until they are needed for emergency care only.

WHY ?
Because a horse with PPSM / EPSM is just as easy to tie up being in a stall.  A horse with PPSM/ EPSM needs to be able to move around as much as possible for its health.  THUS my stalls are for emergencies only.  I do however allow one of the stalls open at all times so my horses can go in and out at any point of the day.

My stalls are an unusual size they are only 11 1/2 by 11 1/2  not the typical 12 x12 or 15 x15. 
WHY because I was watching EVERY penny when I built my barn and making my stalls this size allowed for over hang of my roof with out spending extra money for the roofing etc...   Besides my horses are small for horses.  I am done with warm bloods and will not be getting a trochanter or Swedish warm blood any time in my future! ha ha ha...

As for SAND base.
The Barrier is VERY VERY important. 
And the sand must be replaced or re-seated every six months.

As far as CLAY this is the LEAST drainage of the three here discussed. It will pack down in time and if the barrier is not perfect it will pass through and clog all the drainage underneath creating an ammonia issue / health hazard for your horse.

Clay pools pea more than sand
packs harder than sand
BUT is the cheapest of all materials suggested in the south.


This is just the very base of the stall designs... so more to be discussed tomorrow.