Got manure box built, one pallet at each end, two on each side. Lined with plastic sheeting (cheap stuff I got of eBay, it's too flimsy, I wish I'd have gone for 'heavy duty' now). All screwed together, so I can unscrew one complete side when I need to empty it. 15 (fifteen) sacks of horse manure added in one day [that stuff's HEAVY!], about one third full already. Sensible to cover it when it's full ???. I think so, stop the rain 'washing away the goodness'. Not sure how to cover it yet, still thinking about that one :-\. Pile of pallets on another plot, it seems I've set a trend, which is catching on.
At last I can give advice (on building a manure box) as well as ask for it. May not be good advice, but at least I've got a bit of experience now, that I can pass on.
Welcome to the site.
Well you can cover it with polythene but if you give out advice don't include lining it as you need to let the air in.
I wondered about lining the box, although I've seen other stuff on the net where people say 'line it with plastic'. Seems to me the gaps between the slats on a pallet are too wide, the manure would just fall out (?). Maybe the answer is to jab lots of holes in the plastic, I'll do that.
We did the same but lined it with cardboard as the gaps were quite large, that's now pretty much rotted down but still fills the gaps.
I use cardbord to line the sides of my wooden compost bin, and use two large plastic bags stuffed with lots of other plastic bags (that my mushroom compost was delivered in) on the top to make a removable 'duvet' that keeps the rain mostly out and warmth in. Works for me!