[The Woodman]

I've just read your plan to see if I had missed anything and am sure the advice given by valleyforge is well thought out.

Any ply wood, even marine ply, will delaminate and rot in time when kept in conact with soil, although 13 mm marine ply at around £60 per 8 x 4 sheet may last you a good few years.

If you have no base on your underground chamber, will there be a risk the rabbits will dig under the sides of the ply chamber? I would go for brick sides and consider a layer of chicken wire or similar on the base of the chamber. The mesh can be covered with layer of soil.

If you know a roofer, he may be able to supply offcuts of Tyvek or similar to cover the construction. I would personally be happier with some means of accessing the chamber for the reasons given, I didn't want to mention sick, dying or even dead rabbits but it has to be in the equation somewhere. Perhaps they are clean in their present accomodation beacause you keep it clean - it does look very good.

Using ridge tiles is a good idea but again, beware of digging under the edges.

I think the system would breathe naturally with recourse to electric fans, but the provision of a vent tube wouldn't do any harm.

I think we know what you'll be up to this weeekend!