velux not right

[scrumpyjack]

I am having a roof conversion done and I'm not happy with the fit of the velux windows. There are 2 on the front and 2 on the back. How can I check that they are square? I know they have been put at different heights, , but they also look crooked.
I tried checking with a plumb line but it's hard to judge because of the roof slope.
Can I check with a spirit level? I want to be positive before I blast the builder who is coming to see me on Thursday.
When should the roof vents be fitted? The room is boarded out ready to plaster so they can't be done from inside.
Any advice please--I can do photos if needed.

 

[Magic Man]

A laser level will give you a vertical line on a sloping roof (assuming it's levelled correctly of course)

Could also just measure the distance from each edge to another edge - again, assuming that edge(s) are correct.

 

[scrumpyjack]

A laser level will give you a vertical line on a sloping roof (assuming it's levelled correctly of course)

Could also just measure the distance from each edge to another edge - again, assuming that edge(s) are correct.

Thanks, I might buy a laser level, could be a good investment anyway.
I think the windows are OK and it's just the frame that was made up to hold them.

 

[noseall]

We always fit the velux after tile battening this way you can't go wrong.

As for fitting square, you would normally assume the rafters are true-ish.

If they do look a bit skew on the eye, it is possible to square 'em up. But if you go with the roofing battens you are usually ok.

 

[scrumpyjack]

Well,the conversion company agree that the windows are crooked and set at different heights so they are going to fix them

When should the roof vents be fitted? Mine are still in the box. I would have though they would go in from the inside before the insulation and plaster boarding.