Painting inside summerhouse / shed: Advice, please.

Would think you could do that as it’s inside.
I would, especially if I already had the paint.

If you’re painting on to bare wood then you should use an undercoat first.

We painted the inside of the potting shed with Cuprinol as well, they do some lovely colours. Although we did it before we erected it so it was easier and there were no smells.

I don’t think though that Cuprinol smells as bad as it used to and IMO is extra protection inside as well.

We painted the inside of our summerhouse and just used ordinary Matt paint. It’s been up for 6 years now and still looks just as good.

I think you have to coat the wood first so the knots don’t show through.

You could dilute some of your Matt paint, to use as a base coat, before painting on a further undiluted coat.

The knots showing through might actually be rather nice

If it’s bare wood inside it will soak up the paint like a sponge, so a watered down paint is a good idea for the first coats.

Back in the summer , I painted the inside and outside of my shed and summer house with Cuprinol .

I think that it was the pretty willow shade and I didn't dilute it .
I also did the floor
( boards ) of both structures with it .

It came out well .

I would use it again and recommend it .

Depends whether you mean Pritchard or Hancock

There are a wide range of colours from Cuprinol and others. Normal household matt won't really work, the tannins in the wood will come through. There are some very good wood primers from Zinsser that should work, then you could use a matt of some sort.