I'm trying to sort a shopping list of everything I need for breeding (litter planned for summer) I have a medium/large gundog breed.

I obviously need a whelping box, I would prefer to get one that is easily cleanable and reusable for future litters so any recommendations greatly appreciated!
Also, how big will it have to be? (Bitch is around 21" to the shoulder).
I'm not sure on the best set up wise, I have seen boxes/pens with a sort of partially separated off area in them... What is that for? Because it never looks very big on the pictures!

I will need a pen for when they are bigger and more mobile, I have looked at the croft freedom pen but they don't look very big so seems like an awful lot of money once lots of extra panels are bought?
In my head I have a vision of the whelping box with a pen attached to it somehow (how I'm not sure?) or would it just be better to get a separate pen and when they are old enough remove them from the whelping box totally?

Sorry for all the questions!!

My whelping box is 48x48 for a similar size breed, I use this until pups are 3 weeks old, then detach the front to make it open, and attach a small pen to extend their play area

Current litter is now 7 weeks old and I did invest in the Croft Freedom Puppy Pen, it's done 3 litters so far so well worth the investment IMO

My bitches are on average 24 inches tall and I use a 4 ' x 4' whelping box. Always used to knock them together of wood and then burn them after use, last year bought a Steel City one, it's quite flimsy I have to say but it will clean and it does store easily.

You would not believe my living room when we have pups though as I put up a pen made out of proper outdoor metal kennel panels, 2 metres long, 1,5 metre wide and 2 metres tall!  Only way I could stop the pen being jumped in OR out of. For toy pups (which it is in use for at the moment) they stay in it all along, so that they are safe and cannot get trodden on by the bigger dogs -come out several times a day of course, but for my situation, a lower pen or no pen would have been useless as my adult dogs easily jump 4 feet -that includes some of the toys! The good thing about it is there is room for the big whelping box AND still space outside it for the bitch to get away from the pups. For my large breed I remove the pen at about 3 weeks of age, then the pups have the run of the living room and hall with the whelping box to sleep in, access to other rooms is restricted with gates.  I've never felt a pen would work for pups their size. But I know others do and friends with the same breed use the Big Foot puppy pen which is very strong and big.

Thanks, do you have a link to the big puppy pen? Unfortunately they can't have run of the room hence I need a pen, how do people that leave the whelping box up attach the pen?

I've had a look and the Warwick whelping boxes look quite good...?

This is the pen friends of mine use: http://www.doghealth.co.uk/collections/puppy-pens/products/puppy-pen-run-big-foot
It is very sturdy!

The Warwick and Steel City whelping boxes are the same, I ordered mine from Warwick and it came back with a sticker on saying Steel City.

The Warwick and Steel City beds are made by two entirely different companies.I have the 48" by 48" Warwick bed and used it for a medium sized but very powerful breed.Not the cheapest on the market but very good quality and easy to keep clean.I use Dog Health for pens again very good quality and competitively priced.

I have steel city and would recommend. My 2 have done about 8 litters between them, easy to clean and last for ever.

I drew up a design to scale for my whelping box and had the bits cut to order by a local company specialising in recycled plastic. The side panel measurements are 1200mm x 650mm, the sides are 9mm HDPE, the base is 12mm StokBord (LDPE with excellent insulation), it is easily disinfected, the whole thing bolts together in minutes and can be stored  flat. As I didn't mind some tiny surface scratches on one of the HDPE panels (the puppies would have done that anyway) the whole thing cost me £100, about 40% of what a comparable box would have cost.