Thank you!

I bought a new casement Anderson that is composite. Rain glass, tempered. Works great.

darlene the key is in the window to substrate transistion being compatible to the waterproofing and is spanned and detailed properly via carpentry/flashing/exterior wrap first and interior waterproofing/tile prep second.. Dimensional lumber gets wet on either side and it wont play nice with tile

Thanks so much for the advice. What type of contractor should we hire for this work, waterproofing the window in particular? Can you give me suggestions for questions to ask? I'm concerned about hiring someone that really doesn't know/understand about waterproofing. Thanks so much!

you first need to choose an appropriate window IE vinyl clad that has the ability to be bonded to with waterproofing materials CHOSEN on the shower side or inside.

You should look for a professional general who does window and exterior work that can first rough in install and "flash " the window properly as well as insulate the external wall properly.

Then you hire a professional tile shower builder that is expert at shower window waterproofing because his track record says so.

Theres a list of bullet points to long for this thread.

Spend more time sourcing and hiring less time getting misinformed on various websites.