Here are some photo links for you.
1). Low Curb Brick Curb with NobleSeal TS
2). Low Curb Heated Shower Floor 2" finished from floor to top of curb
3). Low Curb Slate Floor Shower
4). Same Shower better shot of curb
5). Low Curb Marble Curb
Those are the only examples of my showers with low curbs on Houzz.com - most of my projects have none! Hope this helps. Did you know that the 13th busiest discussion on John Bridge's forum is the subject of building shower curbs? Almost 35 people per day given crappy advice (lots by Jim - "The Big Red Shoe"..... That's a lot. Look at Jim's helpful advice on the shower curb discussion - use a film gauge... lol. How about the whole curing part. Tying into the clamping drain part. The rest of it....
A shower curb should only be made from cement, bricks, block or of late for me Concrete Board. Wood should not be used. IF it is to be used it should be stable. Dry. Seasoned. KD. Export grade. If this is not available I would use paint grade plywood instead. Wood shrinks. Wood moves. Wood swells when wet. Concrete does not.