I'll freely admit that I've got a bit of a 'thing' about roofs - I don't much care if the boxes have cracks between 'em, and completely open bottoms are ok if the site is sheltered - but for me, a beehive MUST have a decent weathertight roof.
So - here are a few pics which might give you some ideas. Whether the boxes are Warres, Nationals, Long Hives, Nucs etc - they're basically all the same format: telescoping covers with folded aluminium (ex-caravan) tacked on. Incidentally, all my hives are made from condemned scaffold boards, disused pallet wood, or a combination of both. I very rarely buy new wood - it's far too expensive over here in Britain.
These are my 'standard' Long Hives - 100% rain-proof - I make about 10 of these each year:
The roofs are fairly light - just 4 x pallet planks nailed and glued together, with cheap 'separator' plywood (freebies from the pallet yard) nailed on top, with aluminium tacked around them so ... (the following are nuc roofs, but using exactly the same technique):
Finally, a shot of a few hives which are being kept close to the house for various reasons - as you can see the roofs are all basically the same, with the exception of the double Deep Long Hive in the foreground which has a hinged pitched roof. It started life as a KTBH but was quickly rebuilt to take 14" x 12" frames instead:
'best
LJ