Looking for info on sistered rafters


#1

Hi-
I was going to install skylights into my 16" on center rafters and ordered 14" wide skylights so I could drop them right in-between the rafters. However, yesterday I popped my head in the eave and looked up and saw that the rafters were actually sistered right above the eave, and now I’m concerned that my skylights aren’t going to just drop right in if the overlap of the rafters is more than a few feet.

Can anyone comment on this?

Thanks-


#2

The skylight curb in most instances, does not drop down below the deck sheathing. Its curb and frame anchor to the top of the decking.

It is the finish trip work for the chase that will be affected, but you will still get daylight inside, but with a slightly smaller dimension in the width, like the size of 2 more 2"'s.

Ed


#3

These skylights are actually pre-flashed Velux QVTs 1445 and have framing that drops down into the rafters by 6" or so…so seems like I might have an issue, eh?


#4

you have me a bit confused as too what you mean by drop in between the rafters the skylight goes on top of the rafters and everything is framed down to the ceiling creating a box effect, with sheetrock etc. If the rafters are sistered then this would make your 16 inch on center move over 1 1/2 inches thus not changing the area just moving it add 2 2x4 at the ceiling level = to whatever the rafters are and everything should be fine, the 14 inch skylight should still work. unless there is something I am completely not understanding


#5

On Page 6 of this manual, they state that it comes with a paintable white pre-finished interior.

veluxsolutions.com/inet/lite … penelement

It also states that a flush mounted curb is available.

Get that one.

I never used a Velux skylight that dropped down into the interior chase area and didn’t even know they were available.

Ed


#6

[quote=“ed the roofer”]On Page 6 of this manual, they state that it comes with a paintable white pre-finished interior.

veluxsolutions.com/inet/lite … penelement

It also states that a flush mounted curb is available.

Get that one.

I never used a Velux skylight that dropped down into the interior chase area and didn’t even know they were available.

Ed[/quote]

Your not missing anything ED, if I am not mistaken these are the ones that come pre-flashed with a rubber skirt attached to them.
You cannot wrap them in Ice & water shield due to their design, therefore I do not like them very much.
They are user friendly though.


#7

Often rafters are “sistered” on one side only. So you could sister the flip side of those 2 rafters and pull the existing off, leaving you room to drop the slylight. If they are sistered on both sides don’t touch anything as there may be a need for both. Ed is right about the skylight, ask for a “flush cut” if you haven’t bought one already. The only problem with a skylight that is larger than the whole is that you may sometimes see a reflection in the glass of the unfinished deck edge when looking up.


#8

[quote=“moose186”]Hi-
I was going to install skylights into my 16" on center rafters and ordered 14" wide skylights so I could drop them right in-between the rafters. However, yesterday I popped my head in the eave and looked up and saw that the rafters were actually sistered right above the eave, and now I’m concerned that my skylights aren’t going to just drop right in if the overlap of the rafters is more than a few feet.

Can anyone comment on this?

Thanks-[/quote]

Generally, when you have overlaps in rafters, it doesn’t pass 16" where they meet.

Since you’re going to have to install double headers for the skylight anyway, it looks like you’ll also have to sister rafters to the sides of the already sistered rafters that don’t have them (because the sistered rafters alone won’t be strong enough as they’ll be interrupted jack rafters.

In other words, continue to double up the rafters where you plan to install the skylight and you’ll be more than ok. After that, it’s a matter of which rafter you may need to cut out for the length of the skylight if you need the extra space, but because you know have two fully doubled up sides, this should be no problem.