Skylight Installation

I went through few posting regarding DIY skylight. Saw mix responses regardiing do it yourself. I would like to do this project for my new house's kitchen. The only DIY experience I have is installing the exhaust fan in the bathroom. It did required making a hole in ceiling and roof. It was not that difficult.
I know skylight project will be really big one and will involve cutting a rafter and a joist. I am thinking to use Velux FS104 - 22"X39"). My roof slope is 4/12. My design is located in this link:

http://www.cptracker.com/skylight/sk1.gif
http://www.cptracker.com/skylight/sk2.gif

My questions:
1. Is it difficult to hang sloped drywall on all four sides?

2. Is it difficult to attached double headers in ANGLE for supporting a rafter and a joist?

Let me know your suggestions.
Thanks
sk1.gif
sk2.gif

 

If installing a skylight requires cutting into rafters, consider hiring a contractor.

The following link gives DIY instructions: http://www.creativehomeowner.com/Onl.../skylight.html

 

You're scaring me!! You say this is a new house. Then you talk about sloping all 4 sides of the sheetrock in the skylite shaft. IF the house has engineered trusses, locate the skylites between thos trusses, and keep the side walls of the shafts vertical. DO NOT CUT THE TRUSSES!! I am assuming the skylites are 22-1/2" wide, and your trusses are 24" on center. Now, if you are using skylites that are, say 18" wide (or less) and will be centering them between the trusses, then, sloping the sidewalls is an option, but only to the bottom chord of the truss.

 

Lefty - My house is 40 years old. It's not a truss roof.
Rafters and celing joists are placed at 14.5". I am looking to put 22.5" velux skylight. That's why I need to cut one rafter and a joist.

twelvepole - The link you sent me is very useful and also seems DIY job. Why do you think this can not be DIY job?
As long as I can give good temporarily support to the rafter and joist before cutting them and also put double headers of the same size to transfer load from cut rafter to adjustants rafters why cann't I do this myself.
I was also thinking to attach sister rafter to the adjustant rafters so that they become stronger (since they will be carrying extra loads).
I have a fair understanding of how my structure works but I lack the site experience. I saw some tv shows and videos about framing, it does not seems very difficult but again I have almost no experience in doing this kind of stuff.
What is there that contractor can do better than me?

 

http://doityourself.com/skylights/skyframe.htm

 

Reroofing is a great time to install skylights. However, a truss roof can make skylight installation a lot more problematic. Building codes prohibit any field modification (notching or cutting) of roof trusses. That's because once you cut into any part of a roof truss, you can't trust its integrity. So you really should check with your local building inspector before proceeding. But the easiest way I've found to retrofit a wide skylight without re-engineering the trusses is to reframe the roof around the skylight opening with dimensional lumber just as you would in a stick-built roof.

First, you have to plan the location for the skylight; let's say it's 4 ft. square, and the roof trusses are 2 ft. o. c. Because 4-ft. skylights are sized to fit pretty closely between roof framing spaced 24 in. o. c., you may have to cut through one or two roof trusses to frame out the opening. I actually prefer to locate skylights so that their sides fall in the middle of truss bays and not alongside existing trusses. This strategy gives a little more room for slipping in the new rafters and ceiling joists.

Next, calculate the size of the rafters and ceiling joists that will support the roof where you cut the trusses. I use building codebooks or span tables to determine rafter size and spacing. Before you get too far into the tables, measure the distance between the inside edge of the top wall plate and the underside of the roof sheathing. This amount is the limiting height you will have to work with when selecting an appropriate rafter size.

You should not extend the heel cut on the rafters too far beyond the inside edge of the top plate. Usually, roof-truss height at the top plate limits the rafter sizing to 2x8s or 2x6s. Ceiling joists can be a little taller. Selecting a premium species such as Douglas fir or a premium grade such as select structural might be necessary to get away with 2x6 rafters on longer spans.

If you can't support the roof properly, I suggest going with two 2-ft. skylights or leaving a truss exposed in the skylight shaft. But let's assume you can size the rafters and ceiling joists and move on to the next step of cutting and installing them.

If possible, I remove several sheets of roof sheathing in the area where the new skylight will go, which gives you plenty of room to do the framing. If this option isn't possible, the lumber can be slipped through small holes cut through the sheathing at the ridge, and the framing can be done from inside the roof cavity.

Cut enough rafters for both sides of the roof. Even though you'll be putting the rough opening for the skylight only on one side, you need to reframe both sides of the roof. Double the rafters on each side of the rough opening, and prepare headers and cripple rafters.

Don't cut any roof trusses until you get most of the new framing in place. Without getting too involved in describing the logistics, slide in the rafters, and install them first. When the rafters are in position, hop out on the roof and drive nails through the roof sheathing into the rafters wherever you can.

Next, install the ceiling joists. Then prepare a ridge board that will fit between the roof trusses that will remain intact after you cut the trusses for the skylight opening. Using a reciprocating saw, cut out sections of the top chord of the one or two trusses in the way so that you can slip the ridge board in place. A metal-cutting blade will be necessary to cut through the truss plates at the top of the trusses. By the way, this ridge is not structural. It's merely there to help to transfer opposing rafter forces.

With the ridge in place, the rafters are supporting the roof, and you can cut out sections of roof trusses in the way of the new skylight opening. The rest of the truss can remain. In fact, some parts of the truss have to remain to support the soffit and fascia.

Next, determine the exact location of the ceiling opening for the skylight, and frame in the headers and joists. Mark out the skylight opening on the underside of the roof sheathing, and cut the top chords of the trusses just short enough to allow you to install the headers and the cripple rafters. Be sure to secure all rafter/header connections with metal connectors. Do the same for the remaining segments of the roof-truss chords. Then frame up the skylight shaft. If you're not ready to reroof, schedule the final cut in the roof sheathing and skylight installation just before the new roof is installed.

Contributing editor Mike Guertin is a builder in East Greenwich, RI.

Retrofitting Skylights in a Truss Roof

Don't cut any roof trusses until you get most of the new framing in place

by Mike Guertin

Fine Homebuilding Magazine

Taunton Press. Retrieved 20 October 2002. http://www.taunton.com/finehomebuild...ges/h00045.asp

 

OK -- in a 40 year old house, engineered trusses aren't much of a concern. They were virtually non-existant back then. However, given what you said about your limited experience, I think you would be well served to leave the framing and the installation of the skylite itself to a contractor. A mistake in doing the framing could bring the roof or ceiling down on the floor. A mistake in installing and properly flashing the skylite will result in a roof leak, which can do thousands of dollars in damage. I'm not saying you can't do this yourself. I just want you to be aware of the consequences of what can happen if you get in over your head.

 

i would try and get someone with a little more experience to help.
i have been a carpenter for 25 yrs and i will tell you this project can get a little tricky.
i watched some surgery on tv but i ain't ready to cut anyone

 

Come on now guys I just tore off the roof of my house and tore out the dining room ceiling to make a 2 story house and we had a hell of a time making it fall apart and we were cutting 4-5 rafters at a time. Cutting one rafter and joist will not bring the roof crashing down......it will make a visable sag given enough time if you don't frame it right however.

1st time..... how come you don't buy the # FS 304 skylight? it's made to fit 16 inch rafter spacing and you'll get a wider skylight.

 

I'm gonna jump in with Mike here.....cutting one rafter and ceiling joist ain't gonna end your world.

Last week, I built a chimmney for a buddy's new house and we cut 3 2x6 rafters 16"oc on each side of the ridge board, 10/12 pitch on the front, 4/12 on the back ( big shed dormer on that side),plus cutting out the ridge board and stuck a 2x4 prop under each rafter while we worked.....he was gonna go back and header it up after the chimney went thru.....then we set up a work platform up on the topside and set a pallet with two bags of mortar in a pan + 50 or so block and a 100 brick or so at a time on the platform with a Skytrack forklift, and finally a "box"( 4x4' pallet with 2' plywood sides) of fieldrock for the finish face of the outside and I KNOW that box weighed better than a ton, and the roof didn't budge..

I'll agree, over time, you're gonna get a swag IF you don't go back and header it up properly, but cutting one just won't do much initially.


And as to just staying with a skylight that will fit in a 16"oc bay, you only have 14.5 inches there, and by the time you take off for the skylite frame, you ain't go much of a lite......plus a lot of times, you want to center it in such a way that one or more rafters just gotta go......I did one over a stairwell recently and that was the case.....put in a 22.5" light, but to put it in the bay w/o cutting would have offcentered the skylight to the stairs and looked odd.


Hey Walli....I've done some surgery on my dogs and cows....You ain't LIVED until you've made a bull calf into a steer...(cold sweat here)...I'll try it on a two legged animal if you can find a volunteer .....

 

I agree, to a point, with what everybody is telling you. Cutting one rafter and one ceiling joist is not going to cause your roof to fall in. And, if it is properly braced, it won't even sag. The problems arise if it is NOT properly reconstructed. In this case, it will sag. You didn't tell us where this house is, but is 'snow load' a factor? THAT will determine what needs to be done to "properly brace" it. That is why I suggest you leave the framing to a licensed contractor.

 

You also asked about sloping the sheetrock on all 4 sides. Is it possible? -- Certainly! -- I did it on all three of the skylites I installed in my house. (Also cut one joist and one rafter at each of those 3 locations.) Sloping the upper and lower sides are not a problem. Just cut the angle on the sides of the sheetrock to fit the wall of the shaft. The tricky part is the two side walls. If the shaft is 3' tall on the upper end and 2' tall on the lower end, the lower end will be wider at the top than the upper end. Try standing 2 yard sticks up vertically, 3' apart. Now lean each in 6". They are 24" apart at the upper end, but how far apart are they at 24"?? (28"!)

 

Okay people, here's my question:

My contractor installed 3 Velux skylights in my new home this past summer. I know they don't leak when it rains. But now I have finished insulating everything and waiting for the drywallers to complete their work.

I live in N/W Ontario....extreme temperatures.....and the skylights have now started to leak.

The condensation is forming on the top flashing. I proceeded to insulate this and vapour barrier one skylight to test out what would happen. When I checked this morning the underside was all wet. I want to get the house drywalled so I can be finished by Christmas but I don't want to be repairing rotten drywall in a year's time if these skylights keep leaking.

So, why is there still condensation building up in there when I've insulated and vapour barrier?

Any suggestions would be greatly appreciated.

Ciao

 

Well condensation only results from warmer, moister air hitting a colder surface...so we gotta figure out HOW that is happening.

So when you say "condensation is forming on the flashing" do you mean you're gettin up on the roof and observing it on the top side, or you can see the underside of the flashing around the space the skylite was installed in the roof decking ?

Exactly how did you "insulate and vapor barrier" the skylight ?

 

The insulation and vapor barrier aren't the problem the problem is that you are keeping the house at 70 degrees (F) (And, it will be about 90 degrees in the skylite shafts!!) when it is 20 below (F) outside. Do you have a condensation problem with the windows of the house? If not, it is because the builder knew what windows will work WHERE YOU ARE and what windows won't, and bought them accordingly.

I don't know if Velux (or anybody else, for that matter) makes a skylite that you could install in your house, given the temp. extremes it is subjected to, that won't form condensation.

 

Condensation is forming on the flashing, not on the window. I could see this from inside the house.

These are the windows Velux recommended to me and guarantee they wouldn't leak. I did mention to them that I live in extreme temperature ranges.

Insulation was installed as follows:

1. Foil-double bubble-foil (by rFoil) was put around the entire shaft.

2. Two inch blue Syrofoam insulation was fastened next.

3. Eight inch - R28 - fiberglass insulation was fastened next.

4. Where the flashing shows condensation, foil-double bubble-foil and syrofoam was used.

The problem with the condensation bluiding up on the flashing is on the inside of the shaft. This is a very small area.

Would using spray foam insulation work? Personally I hate the stuff, I always seem to spray too much in an area, and then have bigger problems.

But anyways, any help would be greatly appreciated.

 

With all that insulation, how the heck are you even SEEing the underside of the flashing ??? Where is it still showing ???

 

Well, it started like this....I insulated the outside of the shaft, not the inside, therefore I could see the flashing.

I received a call from Velux, and they asked if the contractor had installed any kind of a roof felt. If the contractor hadn't done that, that would create a problem. If the contractor did do that, the following was recommended.

Spray foam insulation around the flashing and then put a vapour barrier up that will fit into the groove that Velux has for the sheetrock. This will then prevent any warm air from getting out.

It would be kinda nice to get these little bits of info beforehand.

I'll be trying this tonight, and let you know how it works.

That's for all the responses.

 

It's like pulling teeth sometimes to get to the bottom of it....

IF you can SEE the flashing from down inside the house, then OF COURSE it's gonna condense moisture on the flashing.....because warm moist air is hitting the flashing......the "shaft " ain't finished....you keep closing it in until sheetrock or something goes in that groove that runs around the wood frame....and insulation should back up to that sheetrock ( or whatever you're using for a finish material....I've used oak before in addition to sheetrock)

Tn...Andy DadgumDDS

 

Well, the nice thing about building your own home is finally learning everything you didn't know. It's a great shame that manufacturer don't give instructions about how to finish off their products.

That being said, it seems my contractor didn't put the roof felt on. It's a little late now to solve that problem. (Weather conditions....cold, snow).

So, I sprayed foam insulation in the crevices and put the 6 mil poly on. Sheetrock is going in today. But, at least the spray foam has solved the problem for now.

My husband will be crawling up there when the weather gets to -40 if we do get any leakage.

I have discussed with Velux about adding instructions for finishing off the skylights. Do-it-yourselfers would greatly appreciate it.

The Velux rep also mentioned that although the foil insulation is great stuff, it should not be used for skylights. Something about that a poly vapour barrier is better.

Thanks again everyone for your help.

So, unless you have other plans......have a GREAT day!!