aleema

i am insulating an exterior wall in my bathroom, and some of the stud spaces are less than 15 inches one is 9 the other by a corner is less than that. I have r-13 for walls 15 inches wide. Do i just cut it the long way, and risk not being able to staple it on one side. or do i just stuff the whole 15 inches into the 9 inch space. Or is there another batt like insulation less than 15 inches.

aleema

1.Also do i put a plastic water vapor sheet between the batted insulation and cement board that will not be covered by tile or anything?
2.And should i put the insulation behind a tub surround that is going to be nailed directly to the studs?

kok328

You will need to cut length-wise the insulation to less than 15" wide. If you really want to staple the paper to the stud, cut the insulation the width of the opening plus what you need for paper and then cut about an inch of insulation off the entire width but, do not cut thru the paper thus creating the paper edge needed to staple to the stud.
Yes, I would install a moisture barrier all around the entire room.
Yes, I would install insulation behind the tub surround.