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One consideration is summer temperatures.
A lot of people with indoor piggies, keep them indoors year round but have just a run outside (no hutch) and put them out for lawn time when they are there to supervise and when it is cool enough. Bringing them back indoors at night. In the height of summer they may only be able to be on the lawn during early morning and late evening when it is coolest.
If you wish to move them outdoors fully for the summer, then a 5 or 6 foot hutch is needed for two sows. This is their living space and where they will need to be locked in at night. Use of the run is only when you are there to watch them. Hutches can get very hot, very quickly so If you have the option to bring them back indoors during the heat of the day, then do so. Even if the hutch is in the shade, a hot breeze can really heat it up inside so be very careful.
I would recommend that you get a separate run, not one of the hutch/run combos which has a run underneath and hutch on top via a ramp. They are difficult to move. Your run may need to be moved every few days if they are getting plenty of lawn time so being easy to move is important! They can also be difficult to access (you have to climb into the run before being able to get to the hutch) so a separate hutch and run really has its advantages!
For indoor piggies to be able to live outdoors in summer, they need to be built up to it slowly. Start by putting them out in a hutch in the day but still bringing them in at night. Once night times are over 15 degrees, they can stay out at night as well.
My boys live in my shed year round, but summer is a nightmare! They actually move into the house for several weeks during the height of summer due to it being too hot in their shed and on the lawn.
Chartwell hutches are well recommended. You can find these on the Home & Roost website.
Make sure you build up grass time slowly. You can’t just put them on the lawn for hours without first spending a few weeks adjusting their gut to fresh grass. I do this by starting to pick a handful of grass to feed to them in their cages every few days starting around February/March and then building it up if the grass is growing and available/not frozen. Then once it becomes warm enough during April/May and the grass is dry, they start to go in the run on the grass for 5-10 minutes for a week. Build it up to 15-30 minutes for a week, etc etc until they can spend hours each day on the lawn when I’m there to watch them.
Hot Weather Management, Heat Strokes and Fly Strike
Feeding Grass And Preparing Your Piggies For Lawn Time
Keeping Piggies Safe during outdoor time
Member Gallery: Hutches