The Most Important Thing To Do, When Building A Shower Pan
I've seen plenty of tips and advice all over the Internet
and rarely do I find the most important thing that you will need to know
when building a shower pan. Every once in a while I will purchase a book
on home repairs or bathroom remodeling that mentions the most important
thing you need to know when building a shower pan, but I rarely see it
Most people waterproof their shower pan, and never install a sloping surface underneath it. There are a couple of ways that you can waterproof your shower pan. The first and most commonly used one today, is called hot mopping or using hot tar, a thick roofing felt paper. These shower pan seemed to work pretty good, but can crack and start to leak.
The second most common form is using a plastic liner that looks something like an aboveground pool liner. This material works good, but can often rip or tear, if it isn't assembled properly. Each one of these methods, will be more effective if you install a sloping surface underneath them.
This surface will be raised around the perimeter of the shower pan and slope towards the drain. I rarely see anyone do this anymore, but it used to be a common practice. It can be done using concrete or plywood.
Either one of these works out fine, you can even use concrete on top of a wood floor, to produce a sloping surface. However, I would recommend using concrete on top of concrete and using wood on top of wood. The reason for sloping the shower pan area underneath the waterproofing membrane is that any water, that gets underneath the shower floor tile, can safely work its way towards the drain, instead of sitting on the flat surface, for long periods of time.
When you don't install a sloping surface underneath your shower tile waterproofing membrane, you can expect water or moisture to accumulate in flat areas around your shower pan, underneath your tile. The water will also absorb into the concrete or cement that is used to slope the shower floor, directly above the waterproofing membrane.