Thread: Skylight installation

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Originally Posted by Jeff Eastman

Roofer says this installation is wrong but I'm not seeing it. I didn't write up any defects on it. Do you see something I'm not??

A couple of common things with skylights;
If it is over 30" in width it needs a cricket
If the slope is 3/12 or less pitch it needs a 4" curb or more

Also on the bottom edge the flashing should be on top of the shingles, not under them. I could not tell in your picture.

Ah yes, skylights..... I've paid out a few bucks on them before. The real stinger is that you can't always see an improper install in a visual inspection.

I actually had one in my own house about a year after I had the roof replaced. After it was torn apart you could see that the upper 'L' flashing was snipped a bit too far at the crease and it led to a leak. I was surprised how small of an imperfection led to a leak.

And I know.... I probably didn't have to pay for the one I did but sometimes it's just easier.

As for the one in the picture, I don't see the problem either.

Scott
Of course you are correct in saying a cricket is needed if the skylight is => 30". I know it is not our job to design a repair, only to report that a repair is needed, but how would / could one make a cricket for a skylight?

Originally Posted by Scott Patterson

A couple of common things with skylights;
If it is over 30" in width it needs a cricket.

Originally Posted by Rick Cantrell

Scott
Of course you are correct in saying a cricket is needed if the skylight is => 30".

I've been trying to wrap mu mind around that ... where does it state a skylight wider than 30" needs a cricket?

A skylight is different than a chimney or wall in that the wider a chimney or wall gets, the more water which will build-up and collect on the high side of it, however, with a skylight, before the water builds up to a point where it could overflow its flashing (the reason for the cricket) the water would overflow the skylight itself because the skylight is not that high.

Unless I am missing something.

Originally Posted by Jerry Peck

I've been trying to wrap mu mind around that ... where does it state a skylight wider than 30" needs a cricket?

A skylight is different than a chimney or wall in that the wider a chimney or wall gets, the more water which will build-up and collect on the high side of it, however, with a skylight, before the water builds up to a point where it could overflow its flashing (the reason for the cricket) the water would overflow the skylight itself because the skylight is not that high.

Unless I am missing something.

Well, I think that I should have said that anything that forms a penetration in a roof that is >30" should have a cricket. Chimney, skylight, ect. This is to keep the water from overflowing the flashing, just as Jerry pointed out. Most of the skylights that I have seen that are big enough to have a cricket are on commercial projects and the cricket is built into the flashing on the high side of the unit.

Jerry
My first thought was that a cricket did not apply to skylights. So I looked it up in the 2006 IRC
" R905.2.8.3 Crickets and saddles. A cricket or saddle

shall be installed on the ridge side of any chimney or penetration
more than 30 inches (762 mm) wide as measured
perpendicular to the slope..."

Now, how to build a cricket for a skylight?

Notice it is only required if perpendicular to the slope.

Originally Posted by Jim Luttrall

Notice it is only required if perpendicular to the slope.

The only ones that arent perpendicular are the round models...or did I miss something, again?

Perpendicular - Wikipedia, the free encyclopedia

AB=downward slope of the roof plane CD=skylight head flashing in the wiki example

Thanks Scott!

You've presented a whole new thought process to tax the aging brain cells. I never have given consideration to a skylight cricket and have never seen one that I can remember. Now with Rick's IRC post I'm in overload.

No more for today ok?

The only ones that aren't perpendicular are the round models...or did I miss something, again?

Com'on Badir, think outside the box.
Is a square skylight a just a square or a could it be a diamond shape??
How many chimneys have you seen that are on a diagonal in relationship to the roof plane?

The Velox installation instructions for both non-self-flashing and self-flashing skylights make no mention of crickets at any width or orientation.

Looks like what I was missing was the "or penetration".

Originally Posted by Michael Thomas

The Velox installation instructions for both non-self-flashing and self-flashing skylights make no mention of crickets at any width or orientation.

Most that you will see for residential use will be smaller than 30", so it is not an issue.

From what I can tell from the photo, the bottom flashing of the skylight should NOT be under the singles. As is, the water running down the side channels allows for running up under the lower shingles.

Richard

If you look closely, I think we can see the head of the skylight in both photos, if I am reading the lap of the shingles correctly.
If this is the case, then the "ears" of the flashing on each side form dams which would hold water at the head of the skylight rather than letting the water flow down and around the skylight. If the slope of the roof is shallow enough in relation to the height of the obstruction, then water could back up under the shingles or up and over the curb which looks a little short.

sorry, I postet in the wrong thread

Originally Posted by RobertSmith

Is the conclusion of this post that a cricket is needed? The code posted seems to indicate so "...or penetration more than 30 inches"....

Yes..

Skylights are my specialty. As a roofer and NOT an inspector. Over 20 years now in the trade

Ive seen them all, all types, all kinds, manufactured a few, repaired a few, fell through one or two....kidding..

Anyways....

Velux skylights are far the best on the market. Got that out of the way...

A cricket on a skylight. Maybe ? Never seen one. Either commercial or residential. However Ive not seen to many skylights over 30" Ive seen a few though and none of them ever had a cricket

It would make sense to add a cricket to the top side of the skylight greater than 30", but if the skylight is on a 4" curb? Your not going to gain to much of a slope to divert water away.

Curb mount skylights should be set on a 6" curb and NOT 4". Depending on location or climate conditions. Up North? Ice damns. Down South? Heavy tropical rains
Out west? Rains from every direction!

Water rushing down the roof would be less likely to get under 6"

There are a few tricks Ill share with you here in the forum

Weather Guard!!!
Weather Guard rain protector should be used around the entire skylight if you really want to make sure it wont leak. Wrapping the entire curb. 2.5 ft on the roof and .5 up the skylight curb. Corners wrapped just like you would wrap the metal flashings
With weather guard alone, your skylight is now watertight!

Roofers in general are very different from each other and installation practices from Washington DC to Florida and out to Texas are very different. Texas residential roofers being the worst Ive seen EVER!

If your skylight dont come with a pre-manufactured skylight kit Ie: Velux Flashing Kits

A roofer must make the curb flashings.

Pieces needed::
Top pan: Normally manufactured out of 24" .019 Aluminum or .24 galvanized coil stock (glavanize will rust over time) so Aluminum is preferred or copper. With copper you can sodder the corners

Step and counter flashings. Each side should ofcourse have step flashing per shingle or tile or...wood shake...slate...etc...

The bottom pan is nothing more than common apron flashings. Used to terminate a roof to the wall that is horizonal to the roof

With a 4" curb you should add a 1" return (philidelphia edge) to the top of the 4" side to stop water from rushing up under the curb mounted skylight.

A counter flashing should be used to cover the step flashings and yes, the bottom pan should be placed over the shingles and not under. However the reason some roofers do this over the metal method is to hide the flashings. Popular in northern states. I agree that this is a water trap and personally never install a shingle over the Apron flashings.

Ive got a detailed step by step on our website

Skylight Leaks | Skylight Repairs and Skylight Installations

Skylight repairs ?

Make sure you use Weather Guard!

LR,

We use our real names here on this board and not our company names. It gets confusing or would be if we all did the same. Can you please go back and change it on the USER CP for us so we can know you a bit better?

rick

Roger that...will change my name to RICHARD THE ROOFER asap

Originally Posted by LR HOME SOLUTIONS

Roger that...will change my name to RICHARD THE ROOFER asap

Sooo .... either you did not get what Rick said or ...

Your first name is Richard, your middle name is The, and your last is Roofer???

I doubt that.

Just contact Brian at the 'Contact Us' link below and ask him to reset your user name to your REAL NAME, or is that too embarrassing (could lead to embarrassing posts which could be traced back to your business)?

Sounds rough on a new guy, but, then the new guy does not seem to understand simple statements either: As Rick said "We use our real names here on this board and not our company names."

Thanks Scott for the reminder of crickets/saddles for skylights >30" perpendicular. For those in California it's ditto at 2007 CBC- 1507.2.9.3.

Long thread, don't remember who said how do you make a cricket for a skylight. I installed a 2'X8' skylight in my house 30 years ago. Instead of the traditional cricket with a ridge I built it like a dormer shed roof. With a sky light you dont care if the water goes over the top! Never had a leak.

I have to agree with others I dont think I have ever seen a skylight greater than 30in. on a residentail roof. I have however, (especially up here in MN) seen a large number of improperly installed skylight. I agree with Roger, and as a former roofer myself using winterguard (whatever you want to call it) around the skylight properly will prevent future moisture problems.

R308.6.8 ....skylights installed in a roof with a pitch flatter than 3:12 must be mounted on a curb extended at least 4" above the roof.

No cricket requirement that I could find.
The River Pirate

Originally Posted by Rick Cantrell

Jerry
My first thought was that a cricket did not apply to skylights. So I looked it up in the 2006 IRC
" R905.2.8.3 Crickets and saddles. A cricket or saddle

shall be installed on the ridge side of any chimney or penetration
more than 30 inches (762 mm) wide as measured
perpendicular to the slope..."

Now, how to build a cricket for a skylight?

This?

Hi,
Just thought y'all might like to know of a reference book that might help in a lot of the situations I've read on this site. "DeWalt Building Code Reference" from DELMAR Cengage Learning go to DEWALT Trade Reference Series: PAL Publications cost is $24.95 and a lot cheaper than a code book and covers a lot of issues. Has pictures and all kinds of good stuff.
The River Pirate

Judging by the site and the sample pages, looks to be a pretty good book. Thanks for the input, I think I might just check that book out.

I think I've seen them at The Other Big Box store (the blue one). I saw those books at one of those stores, just not sure which one it was.

Funny, I was just installing a couple of Velux skylights into my roof today. I've got the flashing all figured out but a question occurred to me that I hadn't considered before.

Installing a skylight interrupts the air flow from the eaves to the ridge vent in a cathedral ceiling, creating two non-ventilated bays below and above each skylight. What is the proper technique for venting these bays?

A couple of contractors I've spoken with told me to forget about it. My thought is to cut a notch into the rafters just below and above the skylights to allow the air to channel into the adjacent bays. This seems to me like the only way to handle it - am I overlooking some other solution that's painfully obvious?

You want the vent holes above the insulation. Bore a few 1" holes to allow for free air flow from one rafter space to the next.

Thanks, that's essentially what I was thinking of doing. I figured since they would be so close to the sheathing that I would effectively be notching the rafters.

Given the contractors I've talked with have dismissed this, is there any practical way an inspector can check that there is a proper insulation air space let alone no dead bays where the skylights are? Or does everyone just hope the AHJ is looking out for it?

Originally Posted by Richard N. Pinkerton

You want the vent holes above the insulation. Bore a few 1" holes to allow for free air flow from one rafter space to the next.

Are you talking about boring holes through the rafters?

I would be very concerned as to where those holes are located in the rafter span, their size in relation to the rafter size, and their location in the rafter regarding spacing from the rafter edges.

Remember, you are not allowed to bore hole willy nilly wherever you want - treat those rafters as you would joists, follow those boring and notching guide lines (which I think will shoot down what you are suggesting).

Originally Posted by Jerry Peck

Are you talking about boring holes through the rafters?

I would be very concerned as to where those holes are located in the rafter span, their size in relation to the rafter size, and their location in the rafter regarding spacing from the rafter edges.

Remember, you are not allowed to bore hole willy nilly wherever you want - treat those rafters as you would joists, follow those boring and notching guide lines (which I think will shoot down what you are suggesting).

In this specific case it's a cathedral ceiling with 2x10 rafters on 16" spacing, framing members being doubled next to the skylights. The span of the room is 16' giving each rafter a horizontal projection of 8' with a 7/12 rise. The holes/notches would not be within the middle third of the span (which is, conveniently, where the skylights are located).

Is there a better design you're aware of that would allow for ventilation of the bays below and above the skylights?

Not sure how it would look, but have you considered a static vent (Air Hawk) just like you would use to ventilate normal attic space?

I took the rafter span, etc. into account when I suggested the boring of 1" holes. It's not something a building inspector can see during an inspection but proper ventilation is critical to your roofing system.

Originally Posted by Richard N. Pinkerton

Hi,
Just thought y'all might like to know of a reference book that might help in a lot of the situations I've read on this site. "DeWalt Building Code Reference" from DELMAR Cengage Learning go to DEWALT Trade Reference Series: PAL Publications cost is $24.95 and a lot cheaper than a code book and covers a lot of issues. Has pictures and all kinds of good stuff.
The River Pirate

I have the Dewalt Electrical Code Referance book. Compact, covers the major points and then some and has pretty pictures on every page to point things out to clients. Works pretty good and serves the purpose.

Originally Posted by Jim Luttrall

Not sure how it would look, but have you considered a static vent (Air Hawk) just like you would use to ventilate normal attic space?

A static vent would either interfere with the EDL flashing or it would be too far away to be effectual. And I'm quite sure the "look" would be fairly displeasing.

The notching/boring idea seems to work provided it's within the guidelines for notching of rafters. In this case it satisfies the 1/6 depth rule and not in the middle third of the span rule. The rafters exceed what's necessary for snow loading in my area as does the sheathing and ridge beam. Which is all to say I don't think there's a structural issue here but I'm always open to a better way if one exists.

Originally Posted by Corn Walker

In this specific case it's a cathedral ceiling with 2x10 rafters on 16" spacing, framing members being doubled next to the skylights. The span of the room is 16' giving each rafter a horizontal projection of 8' with a 7/12 rise. The holes/notches would not be within the middle third of the span (which is, conveniently, where the skylights are located).

Originally Posted by Richard N. Pinkerton

I took the rafter span, etc. into account when I suggested the boring of 1" holes.

What is missing is 'How large are the skylights?'.

Presuming that you have skylights not greater than 16" (the spacing of the rafters), only the skylights themselves will be blocking the rafter bays.

You stated that the skylights are in the middle third of the span, with an 8' span (96") that would make the middle third 32", the upper third 32" and the lower third 32".

A 2x10 is 9-1/4", making the maximum notch 1.54" (1/6 of the rafter depth) and shall not be longer than 3".

However, "The tension side of members 4 inches (102 mm) or greater in nominal thickness shall not be notched except at the ends of the members.", and, being as roofs have wind loading, which creates positive and negative pressures and loads, "the tension side of the member" is both sides. Which means you should not be notching them.

Now, when you go to bored holes, the bored holes shall not be closer than 2" to the top and bottom edges of the member. I.e., the bored holes will be where the insulation is, meaning no air flow.

From the 2006 IRC.

- R802.7.1 Sawn lumber.

Notches in solid lumber joists, rafters and beams shall not exceed one-sixth of the depth of the member, shall not be longer than one-third of the depth of the member and shall not be located in the middle one-third of the span. Notches at the ends of the member shall not exceed one-fourth the depth of the member. The tension side of members 4 inches (102 mm) or greater in nominal thickness shall not be notched except at the ends of the members. The diameter of the holes bored or cut into members shall not exceed one-third the depth of the member. Holes shall not be closer than 2 inches (51 mm) to the top or bottom of the member, or to any other hole located in the member. Where the member is also notched, the hole shall not be closer than 2 inches (51 mm) to the notch.

- - Exception:

Notches on cantilevered portions of rafters are permitted provided the dimension of the remaining portion of the rafter is not less than 4-inch nominal (102 mm) and the length of the cantilever does not exceed 24 inches (610 mm).

Before address the venting of those rafter bays with the skylights in them, let's find out some other information first:

1) What type of soffit venting do you have or are you planning on installing?

2) What type of ridge or off-ridge venting do you have or are you planning on installing?

Continuous or other?

What method of ensuring that there is an air space above the insulation (to allow for air flow from bottom to top) do you have?

First, the members aren't greater than 4" in nominal thickness, therefore in my reading of the code the exception to the notching rule doesn't apply. Not that it makes a difference here, but the rafters are secured at the plates with Simpson H1 or H2.5 ties. The rafters are attached to the ridge beam with Simpson LSSU210 or LSSU210-2 hangers (with each and every nail hole filled) with 2x4 collar ties just under the ridge beam.

Second, the skylights are Velux FS306 which are 30 9/16" wide x 46 1/4" long. When I said they occupy the middle third of the bay I intended to convey that their location was such that any holes or notches would not be in the middle third of the rafters. The skylights are sized to span two 16" rafter bays each. The cut center rafter is attached to a double header above and below the skylight.

To answer your numbered questions...

1) Soffit venting is Cor-A-Vent S-400 continuous soffit vent.

2) Ridge venting is Cor-A-Vent X-5 continuous ridge vent.

As to your final unenumerated question...

Insulation is Owens-Corning R-30C cathedral ceiling insulation which is 8" deep, allowing for 1" air gap in cathedral ceiling applications. Air gap is maintained using Durovent foam ventilation channels (wish my local supplier carried their proVent product - stapling foam was no fun).

Originally Posted by Corn Walker

Second, the skylights are Velux FS306 which are 30 9/16" wide x 46 1/4" long.

Let met get this straight: Your rafters span 8', with a rafter length of maybe 10'? With 4' of that skylight, leaving 3' below the skylight and 3 feet above the skylight ... and you are worried about trying to vent that 3 foot area?

I guess you could vent them to the adjacent rafter bays, but you will be trying to vent double air through that 1" space, and, after drilling the holes through the rafters, you will need to somehow get that air from the into the Durovent foam channels in one bay to the Durovent foam channels in the other bay. I guess you could whack off a corner of the foam??

Don't forget that you will be limited to "A 2x10 is 9-1/4", making the maximum notch 1.54" (1/6 of the rafter depth) and shall not be longer than 3"."

That means you will be trying to get the air from one 16" x 1" space (16 square inches) through a 3" by 1-1/2" notch (4-1/2 square inches), to join the air in the other 16" x 1" space, which is trying to do all it can to vent that rafter bay. You will be trying to force 32 square inches of air through 1 16 square inch trough, if you can even get the other 16 square inches of air through that 4-1/2 square inch notch.

To me, for what you will be trying to do, and what little, if anything you will gain, not worth it.

Yeah, I read the 4" and did not finish reading that it was "thickness" instead of "depth" - me bad there.

Yeah, I'm not trying to get a lot of ventilation coming through there - just enough to keep a little air moving.

I forgot to mention that rather than using 2x12 rafters I opted for 2x10 with 2" polyiso on the interior ceiling. I did the same with the walls - 2x4 with R-15 batts and 2" polyiso. I have a friend who did his entire house this way and he's able to heat all 1500 sf during our new england winters with a single cord of wood. That's crazy tight. Unfortunately my house is about 130 years older than his, and "tight" is not an adjective I would use for it. Maybe I'll just go around with a dozen cans of that fireblock foam sealant stuff.