Hiya,
It really depends on what materials you've got available to you.
For 3 weaners to pork weight you'd probably get away with 6ft by 4ft floor space, but if you think you'll end up farrowing or keeping more weaners/taking them to bacon size then 6ft by 8ft is more useful (you can reduce the size inside with hurdles or bales of straw)
We built most of ours using curved steel sheets (8 ft wide and 4 ft high) and the ends were made from exterior ply which were easy to cut doors out of and add ventilation holes. 3ft high by 2ft wide will be ample for an opening and having it to one side rather than centrally gives a wee bit more protection from the weather.
We also have some great arcs made from old plastic heating oil tanks - they're great for weaners, but wouldn't be much good for adult pigs. They have the added bonus of a built in floor and are easy to roll around if you want to change the position or site. Lots of hot water and washing up liquid once you've cut the doorway then 10 minutes with a pressure washer to rinse it. They're probably my favourite ones.
For farrowing pens you want a bit more space - around 8ft X 8/10 ft and if you're building it from scratch try and build in a farrowing rail or fixings for a removable one. I'd also suggest making sure the roof height is tall enough for you to stand up comfortably - stooping over or banging your head on a roof trying to quickly get out the way of an overprotective sow isn't ideal!
Everyone will have their own ideal set up, but this worked for us.
Hope that helps a wee bit?
Karen
