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Sloped Shingle Roof Expansion Joints?!

Cambino

Hello all,

 

First time posting...  

So I have kind of a silly project on a fraternity house addition that has a flat roof with membrane and a mansard sloped shingle roof that sits atop the flat roof as an almost decorative roof, if you will.  (all fraternity houses int he US Midwest are traditional/ Romanesque in style-its a bore).  Our job is to put an addition on the back that continues bot the flat roof and sloped roof to maintain the original look, and we will have an expansion joint between old and new.  

Please see attached photo

 

Anyways,  structural said we need this expansion joint to carry up through the sloped roof which will require this big giant hideous curb and flashing almost like two parapets with coping running along the slope.

 

1.Has anyone ever had a situation like this? If so what detail did you use to hide the joint?

 

2. Since the mansard roof is basically independent of the flat roof, is there a way to "float" it over the flat roof and just leave all expansion to the building below?

 

I'm not even sure if this is the right site for technical questions.. any and all responses help!!

 
Dec 2, 15 11:41 am
Flatfish

You don't need a "giant hideous curb" - you can use an "expando-flash" type product that will just look like a dark line.  Talk to a roofing rep.

Yes, your scenario 2 is also possible but difficult (=expensive). Fastening of the new hipped addition would be allow sliding of building below in one direction.  Talk to your structural engineer.

Dec 2, 15 12:08 pm  · 
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Cambino

Thanks 5839,  I was hoping there was a product for this.  It was our roofing rep that showed us the big curb detail, and i knew there had to be something better.  I wonder if the curb is more protective? why would anyone do it that way?

Dec 2, 15 12:51 pm  · 
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t a z

Your vertical expansion joint will be interesting too...

Anyway, the correct solution/product in part depends on how much movement is anticipated.

In seismic country I see Situra RedLine used a lot (with concrete construction...) since it's an engineered membrane that can sustain inches of movement in multiple directions. It might be too expensive, but it's enough to give you some ideas.

http://www.situra.com/redline/

See also Construction Specialties for reference.  Also probably a bit much for this case.

http://www.c-sgroup.com/expansion-joint-covers/exterior-covers

Dec 2, 15 8:41 pm  · 
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Cambino

Its a 1" joint and I doubt much movement at all.  We has CS doing most of the expansion products in the facility currently, I will talk to the rep also today.  Thanks for the help, problem is though even with expando flash that they only details I see by the manufacturer are for flat roof membranes.  no luck on one specifically showing sloped roofs, and I cant imagine this is that rare of a situation

Dec 3, 15 10:36 am  · 
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Flatfish

Johns Manville has details for sloped shingle roof on their website, with the expando-flash joint.

Dec 3, 15 11:37 am  · 
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Cambino
chigurh

get some more room in there for date rape and racist assholes to hang their hats.  

Dec 3, 15 4:15 pm  · 
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greatescape

Seriously chigurh? This was a meaningful thread until you chimed in. Have some class.

Dec 3, 15 7:59 pm  · 
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awaiting_deletion

silly question, but why an expansion joint in the first place? whats the facade and how is the addition attaching there?

Dec 3, 15 8:06 pm  · 
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z1111

masonry, correct?

Dec 3, 15 8:12 pm  · 
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awaiting_deletion

the drawings looks like siding? maybe it's low res.

Dec 3, 15 10:02 pm  · 
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z1111

Olaf, that was a guess on my part, I could be wrong.

Dec 3, 15 10:17 pm  · 
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awaiting_deletion

z1111, your question makes my question make sense....if it's siding, I'm thinking I will learn something?

Dec 3, 15 10:23 pm  · 
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z1111

Yes, maybe the OP could give some more information.

Dec 3, 15 10:28 pm  · 
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Cambino

Sorry for the non response, I ignored this after the date rape comment...

Yes z111 it is brick veneer on the existing, and we are using face brick for the addition. should solve all questions

I really want to show you guys this detail just sent to me by the roofing rep (its crazy),  but I cant remember how to attach a photo...  Can someone remind me how I did that (URL?)

Dec 15, 15 5:11 pm  · 
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awaiting_deletion

the far right icon image button....looks like MS icon for image

Dec 15, 15 8:25 pm  · 
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Cambino, 

Upload the image to photobucket, a website host or something where you can obtain the URL to put into the link. You can't attach it like an attached file. You need it to be accessible from the web via a URL.

You could just place the URL directly to the image here in the body of text that would be clickable by anyone here. Just upload it somewhere that can be publically accessible.

That's all I want to say. I was just perusing and found this interesting because I was wondering why the expansion joint... but okay.

Not to everyone else, don't make it about me. I'm just curious but I am not commenting on this thread so keep focus on the OP. Don't stop on the account of me. Carry on. I am just providing info so Cambino can put image links here as needed.

Dec 15, 15 9:25 pm  · 
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Cambino

OK been busy but I finally did all this guys, literally because you have to see this detail and let me know what you think.  WTF?

http://s1022.photobucket.com/user/cameronwelch16/media/Roof%20Expansion%20Joint%20detail/sect.png.html?sort=3&o=1

http://s1022.photobucket.com/user/cameronwelch16/media/Roof%20Expansion%20Joint%20detail/axon.png.html?sort=3&o=0

Dec 17, 15 5:26 pm  · 
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Cambino

haha... not sure why it is so tiny, if you just copy and paste the link into your browser? Why is this difficult? What bugs me is I did it before.

Dec 17, 15 5:29 pm  · 
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Section:

 

 

Axon:

FIFY

Dec 17, 15 6:48 pm  · 
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gruen
That detail does not have any movement. Complex for nothing.
Dec 17, 15 7:37 pm  · 
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Shingles don't need an expansion joint.

Dec 17, 15 9:06 pm  · 
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Carrera

^+++

Dec 18, 15 12:31 am  · 
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awaiting_deletion

what kind of expansion are we talking about here? is the addition being built in a swamp while the existing on rock. did you ask your engineer why and how much does he need? .....Emseal and good waterproofing and call it a day, this is unnecessary overkill that really doesnt work, especially if the 2x10 is supposed to transfer all the building load expansion. it will fail and fasteneres will come loose and the shingles and wp'ing will fail and you will have a wonderful pathway for water between the walls.

Dec 18, 15 8:24 am  · 
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awaiting_deletion

that literally is a metal flashing joint for expansions turned into wood, go back to metal. the wood is assinine.

Dec 18, 15 8:27 am  · 
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awaiting_deletion

Miles you would be right if those were traditional shingles, and somewhat still right with modern roof shingles, but for some reason I guess the engineer thinks the addition is going move a lot often.

Dec 18, 15 8:31 am  · 
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awaiting_deletion

there are also elastic chemically bonded wp'ing lapping membranes.........have the engineer confirm the expansion dimension if you don't know that you are wasting your time!

Dec 18, 15 8:34 am  · 
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curtkram

asphalt shingles glue themselves together right?  that's probably not entirely correct terminology, but when the sun hits the asphalt it essentially fuses the top shingle to the bottom shingle.  sort of.  so you would want an expansion joint if it is asphalt shingles.  however, instead of building up some big thing, you could just put a bond breaker between the shingles over the joint.

Dec 18, 15 9:39 am  · 
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Don't overthink this. The asphaltic compound gets soft when it's warm. Each shingle is only a foot long. Unless they're doing something incredibly stupid structurally there is no need for an expansion joint in the roof. And if they are, it's an indication of how stupid the design is, among other things.

Dec 18, 15 9:55 am  · 
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awaiting_deletion

Miles it sounds like the engineer is forgetting to put in footings and the water table will cause it to heave and ho. maybe by not putting in footings and this massive wood framed expansion joint they are saving money, because money is what drives architecture.

Dec 18, 15 11:03 am  · 
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curtkram

it's an addition bumped up next to an older existing building.  i don't think there's any questions that the parts won't move together.

Dec 18, 15 11:51 am  · 
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Cambino

Curtkram is correct, it is an addition to an old building so they wont move together, which is why structural is requiring this.  There are footings in the foundation and there isn't too much movement expected +/- half inch probably (assuming).  Miles, all arrogance aside, our roofer wont put his warranty on a roof that doesn't have the proper expansion.  If this was residential, I would say risk it and shingle it over for aesthetics, but the roofer is warranting this for 20-30 years, so he gets the say of how he wants it built.  Over a 30 year period a shingle could easily pop loose causing damage to the wood frame trusses below.  He said the same for the expand-o-flash detail, he has used this before and every last one has leaked within 15 years.  Although this would be nice to have no exposed joint, I doubt we can get that approved.  

The drawing was his attempt at something better aesthetically than the NRCA ASPH-13 detail that is professional practice by roofing contractors:

Dec 18, 15 12:22 pm  · 
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awaiting_deletion

cambino back to my metal argument. recreate the top of the detail above but flush at joint with roof

Dec 18, 15 12:54 pm  · 
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Carrera

If it’s a flat plane why not something simple like the top version shown here….if it were a simple house I’d run a 4’ wide strip of heavy EPDM across the gap in the deck between the two structures and run the shingles up to ¼” of the gap leaving a clean black line.

Dec 18, 15 1:27 pm  · 
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Cambino

Carerra,

That is what we want to do, but it "requires the shingles to be set into a continuous bead of roofing cement on top of the flange", which the roofer says they will not guarantee that type of installation and "knows from experience" it will leak in 5 to 10 years. I would think you could make this detail even more watertight by using a 6' or even an 8' wide EPDM strip.  By the way, this is not a house it is a commercial building, and by flat plane I assume you still mean a sloped roof with not change of pitch, and not a flat roof correct?

Olaf,  I don't understand which detail above you are talking about? Could you give a quick sketch to illustrate your idea?  I don't see how to provide a drip edge, and a place to run the underlayment up and under the flashing if you are flush with the roof.  If we could stay flush that would be awesome!

Thanks everyone for the feedback!

Dec 18, 15 4:14 pm  · 
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If you build the entire building under a dome the roofer probably still wouldn't be happy. Time to get another one.

Sure hope those aren't gang-nail trusses ...

Dec 18, 15 5:09 pm  · 
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Carrera

Cam….yes a sloped roof on same plane, no step, sorry, didn’t study the OP & drawing.

What roofing contractor guarantees anything past 2 years? What roofing contractor is in business after 5 years? Remember that contractors only object to doing things they don’t understand or don’t know how to estimate…that’s when the lying begins.

Forget a fancy detail, do a 6’ strip of EPDM (cheap), use a vulcanized (cured) membrane so it has memory if stretched…no chance water will migrate that far on a sloped roof…apply Grace Ice & Water Shield on top of the EPDM (under the shingles) so nails self-heal….no need to caulk or seal the edges.

When architects hear a structural guy say “expansion” they start thinking “earthquake”, think architects get carried away with this stuff.

Dec 18, 15 9:20 pm  · 
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New construction is routinely attached to old buildings without problem. Detail the framing to minimize movement, lap the roof sheathing, etc. The curb idea is simply asinine. Is structural in-house or consulting? Either way you need a new one and a better roofer. A good one will show you how to do it properly.

It doesn't sound like anyone over there has ever built anything. 

Dec 18, 15 9:47 pm  · 
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shellarchitect

Do the roofs have to be on the same plane? Could make the new roof 12in lower or higher, then use a bellows type expansion joint

Dec 19, 15 9:05 pm  · 
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