i built my wife a potting bench about 18 mos ago. it sat outside on our back deck. when we restained the deck last week, i moved the potting bench and noticed the top coat (GF Exterior 450 top coat) had flaked in one area. i had originally used Behr semi-transparent weather proofing, all in one stain and sealer, then top coat on top of that (all water based). i also noticed the top of the boards were slightly uneven, as in some a little higher than others. when i built it, i ripped pine boards into 2" strips and glued all, using Tightbond lll. i removed top and sanded/planed top so it was flat again. i restained yesterday (2 coats ) and top was left outside to dry. when i brought it in last night, i noticed it had a slight bow from front to back. this morning, i put a level across from front to back and the top had bowed so much, the gap in the center was 5/16" !!
where did i go wrong, as this is VERY discouraging! should i turn it upside down and weight it, to see if it will flatten out or should i just rip the boards again and start all over?
Thanks all !
Rich