Sorry but 20 feet x 15 feet isn't as big as my living room so theres no way you could keep pigs in that size area, they would soon become bored and the area would quickly get pig sick. Even with the additional area of the same size in grass it would soon turn mush. Plus theres disposal of all the poo collected, storage of straw etc.
Have you thought of asking the arable farm next door if you could have a bit of the field that borders your house? or the fields at the back?
Have no problems in you visiting to see our set up, our main pens are 18 metres wide by 12 metres long (approx 60ft x 40ft) so you can see the difference against what you're suggesting. and we use two of these pens per set of fatteners as they quickly get minging!
It sounds like you really want to keep pigs but your main concern has to be their welfare and i'm afraid you need more space.
Mandy
