Is A Flat Roof Is Different Than A Just Another Floor ? - Framing - Contractor Talk

Is A Flat Roof Is Different Than A Just Another Floor ?

 
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Old 05-25-2019, 10:16 AM   #1
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Is A Flat Roof Is Different Than A Just Another Floor ?


https://photos.app.goo.gl/hSFfPDRhUU3mLiUN8

I built the platform and 4 walls for the 8’x7’ shed. I don’t know how to build the flat roof. We want 18” overhangs all around.
I got double 2x4 top plates all around at 8’
I was thinking one way would be to put a third 2x4 top plate on one side and hurricane tie the 2x4 rafters across the short 7’ side with 2x4x10 at 16” OC
Then build 12” or 18” soffit ladders for the other two sides. Tie it together with some fascia.
Sheet and clip the whole thing with 1/2” t&g.

I was going to wedge some closed cell rigid insulation in the rafter bays.

My question is if that is adequate slope?
An extra 1-1/2” over or should I double up on the 2x4s

Is EDPM rubber is best roof for that?
Thanks!!
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Old 05-25-2019, 02:31 PM   #2
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Re: Is A Flat Roof Is Different Than A Just Another Floor ?


I think you got it...just hurr strap on the added 2x4 for slope.

Make up the soffit ladders on roof or ground...set the roof joist back 16" from the edge. That's what you connect to. Could use 2x6 also.

No need for T&G on the roof. 7/16 OSB will work fine.

Put 1x fascia around it. EPDM is a good choice... thinner gauge. Roofing supply will cut to length for you. Just go around the perimeter with termination strips from the roofing supply --- use stainless steel fasteners. 1.5" slope is ok.

Add a couple of opposing 8" x 16" vents high up on the wall, get some air flowing through there.

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Last edited by We Fix Houses; 05-25-2019 at 02:39 PM.
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Old 05-25-2019, 03:20 PM   #3
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Re: Is A Flat Roof Is Different Than A Just Another Floor ?


So your going to lay 2x4 across the span and add another 2x on one side to provide pitch? Then ladder soffits?

Why not put 4x6 on on end to increase the pitch, extend the rafters over the edges for the eave and block in between to close out the exterior? Make lookouts or ladder soffits on gables. Still use hurricane straps with that size eave are bump the sheathing to 5/8". I never sheet roofs with less than 5/8
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Old 05-26-2019, 12:11 AM   #4
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Re: Is A Flat Roof Is Different Than A Just Another Floor ?


A little more slope would be better. 1 1/2" rise over 7' only gives you 3/16" drop per foot. I'd be worried with 2x4 that if the roof sags or you install rafters crown down accidentally you could wind up with a flat spot. Another 2x4 would help a lot.

I'd go with 5/8 T&G under a rolled roofing personally but less is probably fine for a shed. You won't want H clips on the roof for sure.

If you want to support your ladder better you could taper a 2x4 from the plate on the high side down to nothing on the low side on your two side walls but for your span I think your sub facia will support itself with some cross blocking on 16".
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Old 05-26-2019, 04:44 PM   #5
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Re: Is A Flat Roof Is Different Than A Just Another Floor ?




https://photos.app.goo.gl/tEd7fyLRmnzEwu1F7
https://photos.app.goo.gl/hSFfPDRhUU3mLiUN8

https://photos.app.goo.gl/ytaV5sZwnRNe7brD6

So many great ideas.
Rained here last night, anyway...
I have the four walls, so for the roof.
The space is 6'=7"
I'd like 18-24" overhang to hang bikes etc.
so I'm thinking to 1/2" bolt a 4x4x10' to the double top plate on one side
Then lay 10' 2x4 16"OC spanning the double top plate on one side to the bolted 4x on the other. No birds mouth or cutting or anything. Hurricane ties tho.
Then building the ladder soffits on the gable ends.

If I'm going to put some kind of rubber on the roof, what kind of fascia do I use? I never did all this, I'm just an electrician

Last edited by Hospodi; 05-26-2019 at 05:06 PM.
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Old 05-26-2019, 04:52 PM   #6
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Re: Is A Flat Roof Is Different Than A Just Another Floor ?


Quote:
Originally Posted by We Fix Houses View Post
I think you got it..

I think you got it...just hurr strap on the added 2x4 for slope.
If I use a 4x4x10 should I rather thru bolt it to the double top plate?

Make up the soffit ladders on roof or ground...set the roof joist back 16" from the edge. That's what you connect to. Could use 2x6 also.
Can I just support the ladder soffits from the wall and this way I can use 2x4? Already bought the 2x4x10

No need for T&G on the roof. 7/16 OSB will work fine.
I got 1/2" cdx. Should I clip them together then? Is that ok with the rubber roof?

Put 1x fascia around it. EPDM is a good choice... thinner gauge. Roofing supply will cut to length for you. Just go around the perimeter with termination strips from the roofing supply --- use stainless steel fasteners. 1.5" slope is ok.
1xwhat? 1x6? 1x4? How much would raise over the top of the rafter for the roofing? I thought I would just let it shed the water over the side. We have a 12" overhang to protect the bottom. Or do I need to rig some gutters and a spout?


Add a couple of opposing 8" x 16" vents high up on the wall, get some air flowing through there.
Great idea, thanks

Last edited by Hospodi; 05-26-2019 at 05:01 PM.
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Old 05-26-2019, 04:55 PM   #7
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Re: Is A Flat Roof Is Different Than A Just Another Floor ?


Quote:
Originally Posted by Tom M View Post
I never sheet roofs with less than 5/8
So your going to lay 2x4 across the span and add another 2x on one side to provide pitch?
How about 4x4x10 on one side and nothing on the other
Then ladder soffits?
The ladders will support the last rafters for the low side fascia

Why not put 4x6 on on end to increase the pitch,
4x4 ok?
extend the rafters over the edges for the eave and block in between to close out the exterior?

Make lookouts or ladder soffits on gables. Still use hurricane straps with that size eave
I was going to bolt it thru w 1/2 bolts, not needed? straps are ok?
are bump the sheathing to 5/8". I never sheet roofs with less than 5/8

thanks!
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Old 05-26-2019, 05:00 PM   #8
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Re: Is A Flat Roof Is Different Than A Just Another Floor ?


Quote:
Originally Posted by TheConstruct View Post
A little more slope would be better. 1 1/2" rise over 7' only gives you 3/16" drop per foot. I'd be worried with 2x4 that if the roof sags or you install rafters crown down accidentally you could wind up with a flat spot. Another 2x4 would help a lot.

I'd go with 5/8 T&G under a rolled roofing personally but less is probably fine for a shed. You won't want H clips on the roof for sure.

If you want to support your ladder better you could taper a 2x4 from the plate on the high side down to nothing on the low side on your two side walls but for your span I think your sub facia will support itself with some cross blocking on 16".
A little more slope would be better. 1 1/2" rise over 7' only gives you 3/16" drop per foot. I'd be worried with 2x4 that if the roof sags or you install rafters crown down accidentally you could wind up with a flat spot. Another 2x4 would help a lot.
Great idea. Going w 4x4 on the high side and nothing! on the low side

I'd go with 5/8 T&G under a rolled roofing personally but less is probably fine for a shed.
Bought some 1/2" since we are 2x4 w 16OC and the span is just 6'-7". there is the little 24" cantilever eave. Is that ok?

You won't want H clips on the roof for sure.
I was going to clip them together. No good? Why because it could come thru the rubber roof?


If you want to support your ladder better you could taper a 2x4 from the plate on the high side down to nothing on the low side on your two side walls but for your span I think your sub facia will support itself with some cross blocking on 16".
I was going to set it on a ledge to the wall and or kick a brace up from the double stud ends

thanks again!
I post some pix when done.
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Old 05-26-2019, 05:05 PM   #9
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Re: Is A Flat Roof Is Different Than A Just Another Floor ?


Was just going to slope and let it shed.
Overhang should keep base from getting too wet.

How to drain is really the question
how does the fascia end??
The rubber , how does it let the water off the roof?

I guess I just get 1x4 fascia if I have 2x4 rafters
Or do I go 1x6 face and it dangles down under the rafter , cause that might look better?


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Old 05-26-2019, 08:19 PM   #10
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Re: Is A Flat Roof Is Different Than A Just Another Floor ?


You actually want the fascia to be wider than the cut rafters ends . You'll also want to run a strip of ply to box in the eaves.
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Old 05-26-2019, 08:46 PM   #11
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Re: Is A Flat Roof Is Different Than A Just Another Floor ?


Roof --- you don't need ply-clips with 1/2" CDX -- 16" OC

Fascia --- use 1x wide enough to cover the joists --- hang below joists approx 1" -- if you choose to add soffit material...close up the soffit.

The 1x fascia does not sit above the roof plywood --- it's even with the top of the plywood. You drape the EPDM over all sides --- screw on the termination strip 2" below the roof line...then mark a line 1" below the termination strip ---- cut that line off with a utility knife. That would be the finished edge. EPDM look at Mulehide and Firestone EPDM Roof Details.
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Old 05-27-2019, 08:27 PM   #12
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Re: Is A Flat Roof Is Different Than A Just Another Floor ?


What Do you guys think about the radiant barrier half-inch OSB they sell at the depot? I got the clothes cell foam board insulation for the subfloor and I have a roof figured I could’ve use this even for the sheeting on the plywood Wall maybe Your friend has shared a link to a Home Depot product they think you would be interested in seeing.

15/32 in. x 48 in. x 8 ft. OSB TechShield Radiant Barrier

https://www.homedepot.com/p/202106240
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Old 05-27-2019, 08:34 PM   #13
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Re: Is A Flat Roof Is Different Than A Just Another Floor ?


What do you do? Sheet the roof with that aluminum foil plywood and then put your rubber on the top of it? I could’ve sheeted the walls with it too, or what?
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Old 05-27-2019, 08:39 PM   #14
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Re: Is A Flat Roof Is Different Than A Just Another Floor ?


https://photos.app.goo.gl/jVS835QdE4UhkXYa8
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Old 05-28-2019, 08:18 AM   #15
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Re: Is A Flat Roof Is Different Than A Just Another Floor ?


I have no idea why you are insulating this. Insects get into untreated insulation and nest in it. Foam used for insulating foundations is treated to keep insects from nesting, if you want to go that route.

If you're trying to prevent heat build up, cross ventilation at the top of the wall is most important. Radiant barrier decking will help some.
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Old 05-28-2019, 10:40 AM   #16
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Re: Is A Flat Roof Is Different Than A Just Another Floor ?


Yeah the insulation I used between the floor joists is supposed to be insect resistant. For the roof deck I just put 1/2” radiant barrier and then rubber roof over that? Is that an improvement over the 5/8” cdx? I was concerned it was going to get pretty hot in there without insulation on the top deck.

I’m on my way to the Depot to pick up the remaining parts to finish up today I hope
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Old 05-28-2019, 11:04 AM   #17
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Re: Is A Flat Roof Is Different Than A Just Another Floor ?


You can put the rubber straight over the roof deck.

I've only used radiant barrier decking on a well ventilated roof system. It made a difference, but it still got hot. It's definitely better than not having it, just pricey.
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Old 05-28-2019, 12:41 PM   #18
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Re: Is A Flat Roof Is Different Than A Just Another Floor ?


Quote:
Originally Posted by hdavis View Post
You can put the rubber straight over the roof deck.

I've only used radiant barrier decking on a well ventilated roof system. It made a difference, but it still got hot. It's definitely better than not having it, just pricey.
here at the depot, the 1/2" radient sheet is less than the price of the 1/2" CDX

https://thd.co/2JI5jU7
https://thd.co/2HIhIVR

anyways, thanks! i'll post some photos when its done

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