Making Double Tier Hutch - Hole in Nest Area Size Query

I am ordering double hutches for a sanctuary. The size am getting made us 4 ft long 3 ft deep and each level 2 ft high. What size of hole would I need to request be cut in the top area where they will sleep which is sheeted off ie. The door hole to the bedroom. And what size for hole in top floor for ladder ?? I have looked at pics unlined but can't determine size. Want size to be able to accomodate say 4.5kg bun.Also is a slightly pointed roof better than a flat roof??

Not good with weight of bunnies. What breed would that roughly be?
A sloping roof is better for rain to run off if outside.

A medium rabbit (2-3kg) fits neatly through a 6" hole, but to accommodate large rabbits I'd go for 8-9". Rabbits do tend to ooze well through gaps

I don't think a 4ft hutch would be anywhere near big enough for a 4.5kg bun, I'm afraid, even if it was a double tier. It'd be much better to get a 6ft single tier done...it'd probably be cheaper too. Double tiers are fine in theory but the ladders take up the majority of the space sot he bun would simply have no space to hop around or flop out. Even if you are a rescue and the hutches are "temp" accommodation, you need to provide adequate space for them. If you wanted the 4ft hutch then you'd absolutely have to have a run or something attached otherwise the buns will not be getting the space they need to stay happy and healthy.

Thanks for the replies very helpful and liked the "oozing" description! !! The hutch is 3ft deep so quite wide is it not ?? even though I would have liked a 5 ft hutch the pen is only wide enough to take a 4 ft hutch and the pen is 14 feet long which they have access to daily. The sanctuary is within a forest and the buns are locked into the hutch at night and i thought a two tier would give even better predator protect just incase. Or do u think a single storey hutch would be better tho it still can only be 4 ft wide by 3ft deep. Both hutches will be raised off the ground on legs Just want to order what would be best.

In my opinion a single tier would technically give more floor space than a two tier, but it does depend on how the hutch itself is built. I think it more likely that a predator may be able to knock over a hutch if it is a two tier. I read it wrong and thought it was only 2ft deep, so I apologise for that! It certainly would give them more room and I think that would be fine, especially with the pen attached. Although a 4.5kg bunny would be a pretty large bun and I don't think that would be big enough for a bun of that size...although I find it difficult to transfer weight into actual size. Judging on the size of my 2.5kg bunny, I would say a 4.5kg bunny would be quite a large bun and so this means they would need a larger space, however you could judge it by seeing them in it. 4x3ft hutch would be fine for a medium sized bun. Perhaps if you wanted to house larger buns you could think about getting a small playhouse or something similar? I have no idea how much space or money you have; I am just throwing around ideas!

As for predator proofing- I would definitely request that the hutches are double meshed. I would also make sure the hutch is built from very sturdy and good quality wood. What kind of pen is the hutch kept in? Is it an open topped/fold up kind of pen?

The hutches are in an opened topped fenced and wired pen which is about 4 ft high with a gate. Bunny is currently in 4 ft by 1.5ft double tier hutch which is way too small but at least he has free access to the pen which is 14 ft long each day. Am only guessing the bun is 4.5kg as my heaviest is Cody at 2.2kg and this bun is a good bit bigger. I was thinking of around an 8 inch hole for the bedroom. Hutch is to be made from heavy pressure treated pine and using galvanised mesh. So good and strong. Will defo get double mesh. Just was thinking a double hutch would give him some variety or would I be better with single tier and say 4 ft by 4 ft as there is enough room in the pen. I could never figure out how to post pics here but if u didn't mind pm ' me ur email address I could email u a pic of their current set up andthe white bunny is in the foreground so u could let me know ur thoughts. Would be much appreciated.

4'x3' is the same as a 6'x2' hutch in terms or floor area, just squarer I think if you went 4' deep it would make cleaning tricky - you'd need very long arms. So I'd stick with the double height 4x3. As long as there is exercise space too it's not going to make a massive difference. The other option that might be worth considering is a sort of hybid hutch at the top/deeper pen at the bottom so he had a smaller but fully secure pen 24/7 and the the full 14' in the day.