How to do roof with sloped deck AND tapered insulation?

[patricks]

I have a roof with metal deck and tapered rigid going onto existing bar joists. The bar joists are sloped and hence the deck will be also. However I also have roof drains and need certain parts of the tapered insulation to slope in different directions than the deck and structure.

What are everyone's thoughts on making this happen? Right now my roof deck is flat with edited points and variable thickness on the insulation layer, but of course this is not correct.

I thought about doing 2 roofs with the deck separate from the insulation and roof membrane, and joining geometry, but I'm afraid I would have to make the insulation so thick that it might end up going below the deck at the high side of the roof structure.

[mthurnauer]

There are many options depending on what the roof is actually doing. In many instances, there is a uniform base of insulation over the roof deck and then there is built-up tapered insulation on top of the base layer. I have done the uniform thickness as part of the main roof assembly and then modeled the tapered insulation and crickets on top as a separate roof. I did not see a need to join them. We often provide a different surface pattern to tapered insulation so it is clear in plan what is tapered and what is not.

[amindez9667]

I have also separated the crickets (tapered ) insulation for the roof composition. Metal deck rigid insulation and membrane are all part of the roof. You are also able to define a slope ¼”.
On our last project the Crickets (tapered insulation) were not modeled . These were drawn on the roof plan with filled region as we were pressed on time. The only disadvantage was that it will not appear on sections. However sections are not generally referenced for roof drainage.

[cliff collins]

I'll chime in here, with my usual "model it in 3D like it will be built" philosophy.

Start with the sloping joists, and use a beam system and a sloped reference plane to hold them with the slope.

Then place the minimum untapered layer of rigid insulation and metal deck on the joists
as a roof.

Next, place the roof drains at your low points, per the roof plan layout.

Then create the tapered insulation, using point editing, to create the "crickets"
and sloping portions to get drainage to the roof drains. This forces you to think about the slope, and layers/thickness of insulation required. Tapered insulation is not cheap.
So lay it out conservatively. Use BIM to help inform the design, and ultimate outcome.

Now, anywhere you cut a section, you have it "drawn" already.

Just my usual "purist BIM approach"--and 2 c worth.

cheers

[Scott Womack]

Cliff, I can't agree with you more. Only issue is that you cannot "point" edit the insulation/roof, once it is not starting dead flat.

I'd actually create a roof type that was just insulation, and model it in. Possibly by adjusting its height in a section (dead Flat starting), then use the points to raise the crickets up in that separate roof.

[cliff collins]

Scott,

Yep. I just didn't explain it correctly/like you did!

cheers

[patricks]

Yeah, I also agree with Cliff, but like Scott said, no point editing tools if you don't start with a flat roof. Bummer.

*edit* hmm wonder if you could do point editing to a roof that was placed as "flat" but sketched using a sloped ref plane as the work plane.

*edit 2* nope can't sketch a roof footprint on anything other than a horizontal work plane. Double bummer. :(

[cliff collins]

You can have the "dead flat" roof to begin with, but ROTATED via aligning with a sloped reference plane. Then you can adjust the points for the crickets, etc.

cheers

[patricks]

You can have the "dead flat" roof to begin with, but ROTATED via aligning with a sloped reference plane. Then you can adjust the points for the crickets, etc.

cheers

Nope, that doesn't work either. Align tool doesn't work, and rotate tool will tell you it can't change the plane of the roof sketch.

[cliff collins]

Sorry--didn't mean literally use rotate or align commands--

I think you can create the roof by extrusion, using a sloped reference plane as a guide to lock it to. Or, select the sloped ref. plane as active workplane, and create a "flat" footprint roof.

Then if you rotate the reference plane, the roof ( and joists/framing ) adjust with it.

Then use points to edit crickets.

cheers

[patricks]

Sorry--didn't mean literally use rotate or align commands--

I think you can create the roof by extrusion, using a sloped reference plane as a guide to lock it to. Or, select the sloped ref. plane as active workplane, and create a "flat" footprint roof.

Then if you rotate the reference plane, the roof ( and joists/framing ) adjust with it.

Then use points to edit crickets.

cheers

Sloped ref plane, or any ref plane, sloped, flat, named, or otherwise, does not appear to be available to set as the work plane when sketching a roof footprint. If you sketch a roof footprint, align and lock it to a flat ref plane, then rotate the ref plane, it breaks.

Point editing tools aren't available for roofs by extrusion.

I tried doing a sloped roof with min insulation and then another flat roof with insulation and roof membrane only, but they won't join together. It says it can't cut geometry (they're overlapping and one needs to join to the other).

Oh well, the roof is only 18' 8" wide and only drops 2 5/8" in that distance (existing sloped structure built in 1967) so I'll just leave the roof flat with point edits, and then show the deck sloping in my details.

[cliff collins]

Patricks,

Yep--just tried these ideas, and no dice.

Probably need to model in-place, or create a Mass and create roof by Face.
But then probably no point-editing still?

These sound like Wishlist requests......... LOL

cheers

[patricks]

Yeah, point-editing the top surface of a roof while the bottom surface follows a slope (slope-defining line or slope arrow) would solve the whole thing.