Is there any way you could make an opening at the top of one of the doors for them to get in?
Thanks for asking. Answer is no. Its a standard size single shed door. I was thinking of the area just above the door, but there is a 6x2 support there for a mezzanine. I keep looking but see no sign of a nest yet. They keep showing the area off to their friends, so sometimes 5 or 6 birds together.
I hate to lock them out as they've had a hell of a journey to get to Africa and back. I'd have them all over the outside of my house, but the nests keep falling off the wall.
I love watching them and listening to their chatter. Look for them going and returning every year.
If no sign on nesting materials tonight I have to lock up as I leave again in the morning as I work away. I may have to see if I can put an entry point in for them for next year
You could try these George for the house www.nhbs.com/house-martin-nests
When I read this earlier, I assumed it was swallows. They're often mistaken. Not sure there's been examples of house martins nesting inside sheds. If it is house martins, I am pretty sure you'll be fine closing the door.