Bonnie's Doggie Bunk bed Design
This "cot-style" bunk bed doesn't absorb water and is easy to clean.  The top photos are from my 1st attempt.  The design below is my improved version. 

Materials Needed:
2 each:  8' long 2 x 6
4 each:  8' long 2 x 2
4 each:  8' long 2 x 4
4 each:  8' long pvc pipe 1/2"
2" or 2-1/2" long screws (about 50)
​2 Large Coolaroo Elevated Pet Bet Replacement Covers 

1/4" gap between boards------------

Coolaroo Elevated Pet Bed Replacement Cover

(about $12 on Amazon - click on photo to go to order)

Cut four 2x4s 39" long
Cut four 2x2s 39" long
Cut four PVC pieces @ 39" long

Cut four 2x4s 27" long
Cut four 2x2s 27" long

Cut four PVC pieces @ 27" long

Cut four 2x6s 30" long, then cut each corner out 1-1/2" in from the side and 5-1/4" down on both ends to create 4 support braces that look like the image to the right.

Attach the 2x2s first screwing downward into the support braces (longer ones for the sides, shorter ones for the ends).

Next, attach the 2x4s leaving 1/4" gap between the 2x4s and 2x2s (flush to top of brace). Screw in from side of brace.

Slide the replacement cover through each gap and insert the PVC to prevent it from pulling back through.  Alternately, you can place the cover (with the PVC already inserted) on the frame prior to attaching the 2x4s.