Hi Tanya and welcome to the forum
Work on the principle of 1 square foot per medium sized bird for the house and 3 square foot per bird for the run and you should be about right, particularly if you are going to let them freerange for all or part of the day most days.
I'd agree with everyone else here, I'd think the ark is too small - the dimensions given come out at between 6 - 8 square feet (I think - I'm not great with measurements :? ) - if I'm right I wouldn't want to have more than a couple of hens in there. You need to feel comfortable keeping your birds confined to their run if necessary, particularly if you need to restrict their feeding for a while for example.
We spent a
lot of time looking at houses, wanting four hens (it's now five - that's something else you have to be aware of, making sure you have room for at least a couple more than you start off with. Possibly dozens more, as you'll know if you've read some of the other threads on this forum
).
We ended up buying a second hand but unused house on eBay for about £50 and making the run ourselves from lengths of 2x2 and strong wire. Well, I say 'we' - I did the shopping, OH did the building (bless him, love him to bits
). We have the advantage of very secure fencing around our garden so didn't worry too much about the security of the run itself, otherwise we would have invested in welded mesh.
As for position - we didn't want to be moving the house/run around all the time, so they have a fixed place on a patch of bare earth (actually where there used to be a very large shed), with bark chippings and a little gravel inside the run. If they'd been on grass they'd have turned it to mud within hours, so I figured they might as well start that way
Every four weeks or so we move the run, I rake over the wood chips, top them up a bit if necessary, and put the run back. In between whiles I clear up any large amounts of poo on a regular basis - though most of the time that isn't necessary because they do freerange a lot of the time around the garden.
This week they've been confined to quarters though because they haven't been earning their keep (4 eggs from five hens in one week :!: ) and they've been perfectly happy. Well, they grumble like mad when they see me coming, but I know they're just trying it on :roll: Today has been appallingly wet, so they're a bit bedraggled and a little muddy, but I'm pretty sure they'll survive ...
Going back to your post (sorry :oops: ) - I'm not sure what the man meant about parasites - the size of fenced off area sounds great to me, in effect they'd be freeranging; and unless there's a problem with the ground elder I don't know about I'd have thought your hens would be very happy there; as long as they have somewhere to find shade when hot and shelter when wet (though most of them seem to ignore that bit and just get soggy
) and somewhere cosy and secure to sleep at night and to lay their eggs ...
Sorry for such a long winded reply - hope a bit of it helps somewhere along the way :oops: