Entered the loft this morning and could smell ammonia. I am on deep litter and knew ammonia smell is a sign of a leak in the loft. I have 2 breeding sections 8' X 5 at the moment I have cocks in one and hens in the other. I also have a center section 10' X 8' this holds last yrs youngsters. I found in a breeding section a small knot hole close to bottom of the loft. I scrapped back the hempcor to find a small wet patch, I would think about a cup full of water had leaked in. I removed all the hempcor from both breeding sections ad spinkled a little floor white and brushed it in. Looked at the center section which was dry but I will remove this tomorrow and go back to scrapping. A little drop of sillicon sorted the leak. But I was surprised at the amount of ammonia smell a small drop of water could make.

bob its not just a leak if its like that , i would think its got a lot to do with air flow and the very damp weather we have at the moment.

I woukd get it cleaned out asap and get some fresh litter in straight away

It could be more than just this one small leak, I will have to investigate. As I have removed the hempcor from the two breding sections (BTW the floor under the hempcor looked like new)Locked up and returned after a few hours and there is no smell what so ever. But I will remove the hempcor from center section tomorrow and go back to scrapping every day.
I have a few front vents and at the rear I have a 1.5" gap running the length of the loft. I have 4 4'X 1.5' windows which I drop down every day to allow birds to a front 3' X 3' X 20'aviery. I am now thinking maybe a few vents with fans in the roof.

Went in the loft this morning and no smell. I will still fit 4 vents in the roof as you can never get enough ventilation.