Installing New Skylight W/curb On Top Of Old And Bigger Curb - Roofing/Siding - DIY Home Improvement | DIYChatroom


Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Roofing/Siding

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Display Modes
Old 06-10-2012, 03:27 PM   #1
Member
 
Join Date: Apr 2007
Posts: 2,302
Rewards Points: 1,038
Question

installing new skylight w/curb on top of old and bigger curb


my house seems to have had an old skylight which got boarded up before i got it and the covered curb's dimensions are 28.5 x 30. the box was covered with a sheet metal box which has some coating on it that resembles hot tar (very coarse). the rest of the roof has the same coating but the material under it seems more like thick asphalt sheathing, not sheet metal. not that there is no shingle or roof tile on the entire roof, which is very mildly pitched (10 deg max).

my original idea was to get a custom sized skylight but Velux wouldn't accommodate so i went after their standard 2222 model, whose curb is 25.5 x 25.5 on the outside. now i need to mount the new curb on top of the old curb.

here is how i plan to do it:

1. remove the sheet metal cover.
2. remove the lid from the old box
3. cut a new cover with a 22.5 x 22.5 opening to match the new curb, which would act as an adapter of the new to the old box. this will be 3/4" OSB (unless instructed otherwise).
4. fasten the new curb to the adapter cover from the previous step
5. fasten the new curb/adapter manifold to the old box.
6. wrap the new curb with bitumenous adhesive underlayment and sheet metal flashing from the Velux flashing kit as per their instruction manual

however, what i don't know what to do is how to shield the old box that now has the sheet metal covering as shown in the picture. i have to rip it off to adapt the new curb.

my thought is to somehow fabricate a tub-like sheet metal box to set over the old box. but i do not know how to seal and waterproof the edges if i do.

pictures attached.

thanks
Attached Thumbnails
installing new skylight w/curb on top of old and bigger curb-opening_reg.jpg   installing new skylight w/curb on top of old and bigger curb-opening_close_up.jpg   installing new skylight w/curb on top of old and bigger curb-new_setup_placed_on.jpg   installing new skylight w/curb on top of old and bigger curb-curb_cover.jpg  

Advertisement

amakarevic is offline   Reply With Quote
Old 06-11-2012, 01:33 PM   #2
Pro Slate Roofer
 
tinner666's Avatar
 
Join Date: Mar 2005
Location: Richmond, Va.
Posts: 1,611
Rewards Points: 1,038
Default

installing new skylight w/curb on top of old and bigger curb


No velux kit will work on that. Get THAT money back. Assuming the inside frames up good, you just need to make an hour-glass shaped flashing. You'll need to look at my website for flashing details and tin roofing details so you'll know how to fold and double lock the corners into place so they are water-tight. It's doable, but you'll need your thinking/studying cap on!.

Advertisement

tinner666 is offline   Reply With Quote
The Following User Says Thank You to tinner666 For This Useful Post:
amakarevic (06-11-2012)
Old 06-11-2012, 01:59 PM   #3
Member
 
Join Date: Apr 2007
Posts: 2,302
Rewards Points: 1,038
Question

installing new skylight w/curb on top of old and bigger curb


Plan B: what if i scratched the old curb altogether? and put an OSB rectangle lid to cover the opening where it sat. then on top of that set the new curb. the Velux flashing will, i believe, extend to reach to the roofing around, i.e. past the hole. the only question is, does the bitumenous tape and flashing integrate with this type of roofing cause the manual says only shingle and tile.

And then put another layer of the tape over the top flashing to prevent water from coming from underneath it.

what do you call this kind of roofing anyway?

thanks
amakarevic is offline   Reply With Quote
Old 06-11-2012, 02:19 PM   #4
Pro Slate Roofer
 
tinner666's Avatar
 
Join Date: Mar 2005
Location: Richmond, Va.
Posts: 1,611
Rewards Points: 1,038
Default

installing new skylight w/curb on top of old and bigger curb


The bitumus tape may eat a hole right through that torch down modifed bitumin roof material you have there. You need to torch down new roof material around a new curb. Not a DIY proposition to be honest.
tinner666 is offline   Reply With Quote
The Following User Says Thank You to tinner666 For This Useful Post:
Ravenworks (06-16-2012)
Old 06-11-2012, 02:22 PM   #5
Pro Slate Roofer
 
tinner666's Avatar
 
Join Date: Mar 2005
Location: Richmond, Va.
Posts: 1,611
Rewards Points: 1,038
Default

installing new skylight w/curb on top of old and bigger curb


Don't forget to get the refund for that flashing kit. It will not work here.
tinner666 is offline   Reply With Quote
Old 06-11-2012, 02:25 PM   #6
Member
 
Join Date: Apr 2007
Posts: 2,302
Rewards Points: 1,038
Default

installing new skylight w/curb on top of old and bigger curb


Quote:
Originally Posted by tinner666 View Post
The bitumus tape may eat a hole right through that torch down modifed bitumin roof material you have there.
how so ? what is it about the tape that can "eat a hole" ?
amakarevic is offline   Reply With Quote
Old 06-11-2012, 02:32 PM   #7
Pro Slate Roofer
 
tinner666's Avatar
 
Join Date: Mar 2005
Location: Richmond, Va.
Posts: 1,611
Rewards Points: 1,038
Default

installing new skylight w/curb on top of old and bigger curb


Mod-bit is particular about the materials it interacts with. Some cements will eat it up. Dissolve it, in other words.
tinner666 is offline   Reply With Quote
The Following User Says Thank You to tinner666 For This Useful Post:
amakarevic (06-11-2012)
Old 06-11-2012, 03:14 PM   #8
Member
 
Join Date: Apr 2007
Posts: 2,302
Rewards Points: 1,038
Default

installing new skylight w/curb on top of old and bigger curb


so Modified Bitumen is what this is called ?
amakarevic is offline   Reply With Quote
Old 06-11-2012, 03:31 PM   #9
Pro Slate Roofer
 
tinner666's Avatar
 
Join Date: Mar 2005
Location: Richmond, Va.
Posts: 1,611
Rewards Points: 1,038
Default

installing new skylight w/curb on top of old and bigger curb


Quote:
Originally Posted by amakarevic View Post
so Modified Bitumen is what this is called ?
Yes. And it's not compatible with the self adhered SBS version. It's APP, and no, I don't even remember what the two designations stand for. I only remember not to mix them, nor the various other products each is compatible with.
BTW, that opening looks like it used to be a roof hatch when it began life.
tinner666 is offline   Reply With Quote
Old 06-13-2012, 01:43 PM   #10
Member
 
Join Date: Apr 2007
Posts: 2,302
Rewards Points: 1,038
Question

installing new skylight w/curb on top of old and bigger curb


this is what i decided: i will do it elegantly and remove the old curb altogether, cut out a rectangle around the hole, and patch it with OSB sheathing and make a hole in it to match the new curb.

then i will set the new curb on top of it and spread some kind of temporary water-resisting patch (maybe vapor barrier with gorilla tape) as a temporary fix before i can get somebody or myself to do the hot tar. i cannot really afford now to have a pro do it cause i am unemployed.

i need to do this ASAP because my time and money are running out and i need to finish the drywall on the inside of the bathroom, which includes the skylight shaft. i cannot wait until the outside is all done in its final state.

QUESTION: how big of an area should i cut out around the old curb to make it optimal for the mod-bit roofing patch ? i am guessing i need to give some slack around the hole, maybe 6-12" on all 4 sides but i am not sure how much. if you can advise so i can proceed with this project, i would appreciate it.

thanks

Last edited by amakarevic; 06-13-2012 at 01:45 PM.
amakarevic is offline   Reply With Quote
Old 06-13-2012, 03:29 PM   #11
Pro Slate Roofer
 
tinner666's Avatar
 
Join Date: Mar 2005
Location: Richmond, Va.
Posts: 1,611
Rewards Points: 1,038
Default

installing new skylight w/curb on top of old and bigger curb


No slack needed. Cut flush and set the box on top of the mod-bit. Put a bead of geo-cel or Karnak 19 Ultra under the box for added protection. Use EternaBond for your temp patch-work.

Last edited by tinner666; 06-14-2012 at 03:50 PM. Reason: typo-Changed 'flash' to 'flush'.
tinner666 is offline   Reply With Quote
The Following User Says Thank You to tinner666 For This Useful Post:
amakarevic (06-13-2012)
Old 06-13-2012, 03:45 PM   #12
Member
 
Join Date: Apr 2007
Posts: 2,302
Rewards Points: 1,038
Default

installing new skylight w/curb on top of old and bigger curb


unfortunately, i do need to cut slack because the 100 y.o. pieces of 1x that were used in place of what today would be OSB sheathing are kind of wobbly and need to be replaces. so i would need to cut at least about 6" on all 4 sides.

so can i do this and can the new mod-bit that will cover the perimeter be somehow either welded or seamed or taped to the old?
amakarevic is offline   Reply With Quote
Old 06-13-2012, 03:57 PM   #13
Pro Slate Roofer
 
tinner666's Avatar
 
Join Date: Mar 2005
Location: Richmond, Va.
Posts: 1,611
Rewards Points: 1,038
Default

installing new skylight w/curb on top of old and bigger curb


Quote:
Originally Posted by amakarevic View Post
unfortunately, i do need to cut slack because the 100 y.o. pieces of 1x that were used in place of what today would be OSB sheathing are kind of wobbly and need to be replaces. so i would need to cut at least about 6" on all 4 sides.

so can i do this and can the new mod-bit that will cover the perimeter be somehow either welded or seamed or taped to the old?
In that case, cut what you need, and then cut what you remove to fit and lay it in place as a filler. Then use the eternabond over those cut seams too. As to it's longevity, etc, I have no clue.
tinner666 is offline   Reply With Quote
The Following User Says Thank You to tinner666 For This Useful Post:
amakarevic (06-13-2012)
Old 06-14-2012, 02:56 PM   #14
Member
 
Join Date: Apr 2007
Posts: 2,302
Rewards Points: 1,038
Question

installing new skylight w/curb on top of old and bigger curb


OK, so i removed the old curb. the next problem is that i do need to expand the perimeter of the cutout in the old mod-bit roofing. however, the thickness of the cover increases as it approaches where the old curb was, it is close to 2" thick. i need to remove maybe 2-3" on 2 sides so i can fit the new curb (it is not exactly in the center of where the old curb was, i.e. a little lopsided).

so the new question is: how do i make the trim ? it's gonna take a hell of a long time to do it with a utility knife, even a hooked roofing knife. is there an appropriate 4.5" grinder blade that can be used for cutting bitumenous materials? there is also sheet metal underneath.

please see the pictures.
Attached Thumbnails
installing new skylight w/curb on top of old and bigger curb-curb_off_edge_1.jpg   installing new skylight w/curb on top of old and bigger curb-curb_off_edge_2.jpg   installing new skylight w/curb on top of old and bigger curb-curb_off_edge_3.jpg  
amakarevic is offline   Reply With Quote
Old 06-14-2012, 03:53 PM   #15
Pro Slate Roofer
 
tinner666's Avatar
 
Join Date: Mar 2005
Location: Richmond, Va.
Posts: 1,611
Rewards Points: 1,038
Default

installing new skylight w/curb on top of old and bigger curb


Skilsaw, disposable wood chisel, straight edged knife and hammer. Any fast blade will gum up pretty good too. They may make a toothed angle blade, but I'm not sure about it.

Advertisement

tinner666 is offline   Reply With Quote
The Following User Says Thank You to tinner666 For This Useful Post:
amakarevic (06-14-2012)
Reply

Tags
skylight , waterproofing


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





Top of Page | View New Posts