Archinect
anchor

Stl. angle at Roof Deck?

shellarchitect

I just looked through some of our current sets and saw steel edge angles all over the place supporting the edge of metal decking... so now I'm curious - what should we be using instead?

 
Feb 19, 15 12:56 pm
snooker-doodle-dandy

I always use Sky Hooks.

Feb 19, 15 1:06 pm  · 
 · 
wurdan freo

Sounds right to me.  Hard to comment without the detail.  Slab edge? Or just supporting the deck?

Feb 19, 15 1:09 pm  · 
 · 

That's how we typically do it as well.  What is the concern?

Feb 19, 15 2:13 pm  · 
 · 
Saint in the City

I usually just toenail the roof edge and bend the nails over for a finished appearance...  (Curtkram -- that was in jest.  I don't really do that. )

shuellmi -- are you talking about using the angle as opposed to another truss placed close to the wall?  Carrera brought that up on another thread...   as in, it's often easier and cheaper to simply add the truss.  It's a good argument, and you definitely see many many cases where there is a truss close to the wall instead of an angle. 

In terms of efficiency, I think it may depend on several things, including the size of the trusses, plus whether you have masonry bearing or steel frame, etc.  At some break-even point, I'd guess it will probably be cheaper to use the angle rather than add another big truss to hold up just a few feet of roof load.    As in, with a 12" truss, I'd guess I'd add another truss.  With a 38" truss -- gotta think use the angle.

...thoughts? 

Feb 19, 15 2:55 pm  · 
 · 
shellarchitect

sorry, i should have specified that this was is response to the parging thread, didn't want to derail the conversation there....

i guess if the angles come on a separate truck from the rest of the truesses anyway can't they be delivered early and installed as the walls go up?

Feb 19, 15 3:32 pm  · 
 · 
b3tadine[sutures]
How far is the deck hanging out past the structure? I'm thinking that the edge of deck is pretty flimsy, plus you'd have something to attach your wood fascia to...
Feb 19, 15 4:21 pm  · 
 · 
I'm curious and looking for you all to help educate me, but why are we worrying about this? I could see this issue coming up perhaps with a project delivery method where the contractor (engaged during the design phases) expresses a desire for a particular detail to aid in sequencing and scheduling.

However, for the most part we seem to be making assumptions based on what I would consider poor scheduling and coordination from the GC on the project cited in the other thread. In most construction relationships, this is the responsibility of the contractor ... not the architect.
Feb 19, 15 8:16 pm  · 
 · 
awaiting_deletion

shuellmi is this what your referencing...best I could do Googling...i think it is close to what you via Carrera were describing...

pour stop? beta

Feb 19, 15 8:34 pm  · 
 · 
Carrera

Jesus Christ you guys... after reading my post if you keep doing this call me and I'll fly out to your office and punch you square in the face. Look at Olaf's top drawing, that's similar to my scenario, mine was with joists parallel to the wall, joist spacing stopping short of the wall and the deck spanning from the last joist to a wall angle... the joist is cheaper than the angle. In Olaf's case it's replacing one of three things - a joist pocket in a CMU which is essentially free - a steel beam, maybe a wash - or is tilt-up and may be essential. But look at all the components in that drawing, all but the angle is erected with a crane... that detail could add a day or two to the schedule.... it would have to be done ahead of the steel erection.... do you know what two days cost in a construction schedule? You could get the mason to set the angle but he probably won't and if unions are involved its iron. The problem is people that do this have never built anything.... lets meet at Olaf's house, I'll bring a 20' angle and two of you can lift it up over your head, carry it up a pair of 40' ladders, hold it in place with your teeth and start drilling holes in the wall - after 4 hours of that you will conclude as I did that it is a stupid idea.... stop doing it!

If you're young and thinking of a job change consider working as a construction super for a year... pay is better and when you go back to being an architect you will be a better architect. This idea that it's the contractors problem is exactly why they think we're idiots and tell our clients we're idiots.

Feb 20, 15 12:03 am  · 
 · 
awaiting_deletion

Carrera, calm down - I Googled it.  Those aren't my drawings....

I have a set somewhere for a mall in Florida, but I signed a disclosure - can't post, it's a better detail...

But i have an image of what you're saying now...I'll keep googling.

Feb 20, 15 12:13 am  · 
 · 
awaiting_deletion

but you did Answer Everyday Interns question.

 

knowing how to build is apparently important enough to be paid better.  funny how that works.

Feb 20, 15 12:19 am  · 
 · 
Carrera

Olaf... didn't mean that they were "your" drawings in that sense.

Answer to his question (in other words) is that I should/could have had the angle installed the day prior to smooth it out but the total number of hours/days would have been the same, it was 3 days either way..... point is I could have done it in 2 days without the angle, and these things are not for the contractor to figure out it's for us to figure out.

Feb 20, 15 1:02 am  · 
 · 
awaiting_deletion

Got it.. I hope the kids are paying attention Carrera, your last sentence is sound advice. Not paying attention to these things is in my opinion one of the reasons our profession feels like it has lost value.

Feb 20, 15 7:14 am  · 
 · 
shellarchitect

Olaf - My office uses something like those top two details pretty much everywhere and I assume has done so for 30 years!

Carrera - almost spilled my coffee reading your "nose punching post"

Feb 20, 15 7:53 am  · 
 · 

The top drawing shows one edge of the deck assembly bearing on some bolts. 

That is a reciepe for failure.

Feb 20, 15 8:42 am  · 
 · 
Saint in the City

If the top one is precast concrete, which is looks like it is, bearing on studded embeds / plate (bolts) is a standard detail.

Feb 20, 15 9:18 am  · 
 · 
curtkram

here is a truss bearing on a hole in the block wall.  they still ran edge angles between the bearing points.  you can kind of see at the corner the angle goes all the way around the perimeter

i don't think the angle is just there to hold up the deck.  it also acts as a pour stop for the concrete, which can be done with lighter material like this

but you would have to attach that to something fairly strong, such as the beam shown here.  i'm not sure why having a joist instead of an angle against the wall would be better.  if you put concrete on top of the deck, it will be very heavy (heavier that before the water evaporates out) and flexible.  that can cause the edge of the deck to bend, especially in the direction the deck does not want to bend.

here is a revit detail i found while looking for these pictures

i believe the edge of slab is held up by magic in this scenario.

Feb 20, 15 9:41 am  · 
 · 
b3tadine[sutures]

Not every metal roof deck gets concrete. 

I think the angle, in the above photo, if it's just metal deck with poly, is excessive. Metal deck can span 5' without that kind of edge support. However, that's based on limited info. 

I hate the idea of joist at the wall, supporting the deck edge, sloppy mess IMO, especially if it's in a gymnasium, or multi-purpose space. I mean how the frig do you paint the wall, or joist - if they are different colors? I'd prefer beam.

Feb 20, 15 10:05 am  · 
 · 
curtkram

maybe the need the extra support at the edge for snow load.  it looks like they might have a bit of a parapet, but not very tall. 

metal deck has a bendy direction and a not bendy direction.  you might be able to get a little bit of a cantilever along the non-bendy direction, but it will need support in the bendy direction.  that's architect words.

the flutes in the picture above would span perpendicular to the trusses, so the bendy side would sit on the angles along the wall with the bearing points, or the wall that's mostly shown in the picture.  i suppose the question is more whether the angle that is only seen a little bit at the corner is needed?  it looks like the last joist is something like 5' of the edge, so in this case the probably do need the bearing point.  it would be a question of buying an angle or placing an extra joist closer to the wall.  i would think the angle is faster and cheaper, if the contractor has a smarter way to place it rather than having a guy lift a 20' angle over a couple days.

Feb 20, 15 10:15 am  · 
 · 
b3tadine[sutures]
Curt, true about the bendy direction, however it's rare that you'd step on the bendy direction, until poly, protection board and any two by infill is in place, which of course would stiffen the edge of bendy.
Feb 20, 15 10:47 am  · 
 · 
b3tadine[sutures]
The other thing to note is that it appears that deck and /or structure slopes in different directions.
Feb 20, 15 10:49 am  · 
 · 
Saint in the City

it would be a question of buying an angle or placing an extra joist closer to the wall.  i would think the angle is faster and cheaper,

Awww, snap Curtkram.........now you're going to get a punch in the face from Carrera.  He's even going after Olaf, but I think she'd take him.

if the contractor has a smarter way to place it rather than having a guy lift a 20' angle over a couple days.

No. There is no smarter way .  (Never mind unknown gizmos like the one the guy is standing on in your 9:44 photo.)

Feb 20, 15 11:08 am  · 
 · 
Carrera

That picture with the guy on the left is priceless, jobs shut down, tink-tink-tink all day, wish I had the time to run the numbers on that operation. A perfect example.

While there are varying conditions, figure out ways to avoid bolting things to a wall. I like the light gauge pour-stop material which can be installed right along with the deck. In that same picture for some unknown reason an angle may have been needed, why not finish erecting the joists and throw the angle on top of the joist and tack-weld to the joists. If painting is a concern use a little beam.... just stop bolting angles to walls!

Feb 20, 15 11:23 am  · 
 · 
slowhare414

Please note that a deck edge angle is for more than just vertical support... it often is essential part of the diaphragm and transferring shear to the walls.  Although there are some situations where it could be excluded, maybe you need to make sure your structural engineer is ok with it.

Also for the edge angle parallel to the joists, if the joist spans are significant, the deflections under full loads may be more than you want to account for in the flexibility of the flashing etc.  (L/240 on a 30' span = 1.5" at midspan).

Feb 20, 15 11:23 am  · 
 · 
curtkram

looked into that picture i posted further, and they did a pretty good job of detailing the construction.  credit goes to the fine folks at the san jose first united methodist church

there is also a first floor ledger angle with rebar embedded in the wall.  this is more likely part of a composite deck.  looks like they more or less pounded their nails up, the way saint advised earlier (j/k)

these kind of show the deck on the angle

and an aerial of the roof being put on

Feb 20, 15 11:33 am  · 
 · 
Saint in the City

Whaddya think, Carrera -- another crack in the face for Slowhare?

Feb 20, 15 11:34 am  · 
 · 
Carrera

Curt's second picture - could it be anymore complicated? Detailing performed by a child.

Feb 20, 15 11:41 am  · 
 · 
curtkram

why do you say that carrera?  do you have any idea what it was suppose to look like in the end, or what they were trying to do?

Feb 20, 15 12:01 pm  · 
 · 
b3tadine[sutures]
Slow, I was thinking the same thing, but wouldn't the angle be flipped, and welded to the top of joist, and not broken by the beam pocket? It seems here, in the latest photo, all it's doing is supporting the deck edge.
Feb 20, 15 12:06 pm  · 
 · 
curtkram

the deck would be the diaphragm if that's what they're doing

Feb 20, 15 12:10 pm  · 
 · 
shellarchitect

perhaps the goal was the maximize the size and type of horizontal steel?

Feb 20, 15 12:14 pm  · 
 · 
Carrera

Curt, of course not, but with architects generally professing to be modernist simplicity should be a mindset translated even into a buildings gut.

Feb 20, 15 12:21 pm  · 
 · 
b3tadine[sutures]
Wouldn't the deck be welded to the angle then?
Feb 20, 15 12:21 pm  · 
 · 
curtkram

beta, i would think so

carrera, it wasn't my design.  i have no idea who did what or why.  looks like the architect might call themselves 'vitae,' but this conversation might be more about the structural engineer's decisions. 

i would prefer to give them the benefit of the doubt, as the other option would probably be to make assumptions that are likely incorrect.  having said that, i do enjoy trying to reverse engineer their thinking, as it sort of helps me learn more about how buildings go together.

some floor plans (more marketing that construction).  looks like part of the roof is occupied, so that might change the thought process too.

http://www.sanjosefirst.org/about/building/building_may2012.pdf

Feb 20, 15 12:30 pm  · 
 · 
"This idea that it's the contractors problem is exactly why they think we're idiots and tell our clients we're idiots."

You mean it's not because we don't know what our agreement says, nor the contractor's contract we are supposed to administer? While not exclusive throughout the industry, AIA documents clearly place sequencing and coordination with the contractor. Look somewhere around Article 3 in A201.

I'm not saying your idea isn't good. I'm saying don't worry so much about it. Do you how much time we would all waste if we tried to redo every detail trying to anticipate (or dictate) how the contractor is going to do their job?

Don't get me wrong. Constructability is important, I'm not saying it isn't. The design needs to be able to be built. I just think that for things like this our time is better spent elsewhere. If the contractor thinks they can do better, let them propose a substitution. And when they do, don't get bent out of shape because it isn't what you drew. And let them quantify it as a credit to the owner. Then we'll really know how much better it is. At least until the next contractor wants to do it some other way.
Feb 20, 15 3:52 pm  · 
 · 
Carrera

There is no substitute for an architect knowing how a building is built, its construction sequencing and understanding which trades do what. There are benefits to this and the simplification of guts, it saves money, time ($), aggravation and latent defects. Realize that a lot of these complicated things come from the engineering side, but you need to look out for them.

Learn to eliminate entire trades or categories of materials – simplified example would be to heat a house with electric baseboard heat…the house still gets heated but you’ve eliminated an entire trade (HVAC). There are great economies in doing this. I obviously have no idea what’s going on in that picture, but eliminating that bar joist (girder) would be a good place to start. Not all buildings can be as simple as this (first photograph) because it often needs to be like this (second photograph) but if you don’t strive to simplify the guts then some GC is going to value engineer your Grohe faucets out of the toilet room.

Feb 20, 15 5:09 pm  · 
 · 
awaiting_deletion

Every Day Intern the way I look at it is as follows - if you operate solely based on the contract the end product won't be as good as it can be if you took Carrera's advice and your dependency on the contract is now even greater if something fails. When you are learning to be an architect it's hard to consider what the trades and contractors do and would be time consuming for you to think like a contractor, but once you get a work type down its easy for you to think all the way into the future of construction and in a matter of 5 minutes make a note and spec that saves the client time and money. Like an engineer I know always says "5 minutes of work plus 40 years of experience"...

Feb 20, 15 6:43 pm  · 
 · 

Again, educate me please ... why would depending on the contract have any negative affect on the outcome of a building?

Also, when something fails wouldn't you want to be able to depend on the contract to defend your position?

I've never heard of anyone getting sued because they followed the contract. On the other hand, if over the contractor's objections you directed them to do things your way, now you become liable for any issues that happen because of it.

We know both ways work just fine. If the structural engineer has a preference ... let them do it their way. If the contractor thinks they can save a buck doing it their way, let them take that responsibility and submit a change order. But why would you want to stick your neck out there and assume you know better for a reason that isn't even your responsibility and step outside the protection the contract affords you?

On the other hand, if the design of your building depends on the truss either being there or not being there (like b3ta's example) go ahead and get it in the documents and make the contractor follow them. That is your job, and you can defend that position professionally exactly because it is your job. Your client and their contractor may not agree with your aesthetics, but they can't really say it isn't your job to care or worry about it. 

Feb 20, 15 11:07 pm  · 
 · 

As for thinking like a contractor, save that for things that really make architects look bad. Things like detailing a sealant joint where it is impossible to install. Or showing spray-applied fireproofing in areas where the installer can't get their gun. Or specifying crack isolation membrane where you already have a waterproofing membrane under tile.

When we can start to consistently get those type of things right, maybe the contractors will be willing to listen a little more when we try to tell them how to save some time.

Feb 20, 15 11:22 pm  · 
 · 
slowhare414

Honestly, I don't have the time or capability to write a thesis in this forum on the structural  analysis of every building situation that could be conceived of for a roof diaphragm.  However, for the situation where the edge angle is perpendicular to the joists,  what is typically necessary will be a deck fastening condition that is adequate for the shear.  ( if you need a certain amount of deck side-lap fasteners...then certainly you'll need  a similar amount of deck weld spots at the perimeter--at a minimum.)... then, if the shear is high, you'll also need to make sure the joist roll-over and shear capacities are adequate--particularly an issue if the joist seats are >2.5"--but a necessary check all of the time.

Although not usually an issue, the the deck edge angle can work as the 'flange' of a beam in the diaphragm.  Please see the diaphragm analysis from a steel deck manufacturer literature for more detailed info.

My point on asking the structural engineer is simply, ASK!...maybe in a given situation it is ok, but don't assume it is.

Feb 20, 15 11:32 pm  · 
 · 
awaiting_deletion

everyone needs to calm down a wee bit....

yeah, Architects will ask the engineer and sure we'll let the contractor propose a solution and we are absolutely working based on contract as far as the paperwork is concerned. we control the paperwork...we are writing the history according to the law for any project.

but there is a lot of shit you can do with a telephone call, an in person discussion, a pre-game Value-Engineering detail, etc...

only the Architect has enough knowledge after years of experience to take the mild risk that Carrera is proposing due to cost and time issues and doing the right job for the client.

An engineer is a train conductor, one tract mind, blinders...well most...there are some 'out-of-the-box' thinkers

A contractor tends to have the biggest ego and best wit and nearly always looks good in front the client even if they are full of shit...except patient and experienced clients, they can smell the fast talk bull shit from miles away.

@Everyday Intern - there is the paperwork and there is the social and I don't mean social media, I mean the face to face and knowing what freshly sawn wood smells like in the morning when you walk onto a job site....I mean the fresh smell of napalm in the morning (movie reference)

This one time, an architect I know rented a van to deliver tile the GC said he couldn't deliver on a Sunday so the place could open Wednesday.  This is the stuff that makes clients remember and trust you beyond the formalities...

The architect is in the position to take the job to the next level outside the formalities or can regress and in fear huddle behind their AIA contracts. 

We kind of float between the laws of physics and finance and we can choose the right path somewhere in between and drop some art while we are at it.

I'm sure a cat like Carrera has taken some risks as an architect and done alright.  I mean he's yelling at me and willing to punch some of us in the face for not thinking ABOUT EVERYTHING ALL THE TIME...I may be mistaken but Carrera made MILLIONS being an architect (somewhere you said this on the forum)...

I believe him because I know an architect who has made MILLIONS because he does everyone's job - Engineers, contractors, etc...like a damn MASTER BUILDER.

 

wait, why am I still working!

good archinect PODCAST btw, Palm Springs is a nice.

Feb 21, 15 12:00 am  · 
 · 
Carrera

Everyday - because of my construction activities I, as an architect, have seen more CD's from other architects than most. I would divide what I've seen into two schools, one are those that draw vary little, lay out the parameters and leave the details to the contractor. The other are those that sweat the details. I think the first group are hoping for a miracle and I've seen miracles. I guess the idea is if I don't draw it and the contactor puts it in you are protected. I think you are from Canada, but down here if anything goes wrong you're getting sued, attorneys down here wipe there assess with AIA contracts. 

I don't think that your choosing between a wall angle and a bar joist is a contractual.issue and I don't agree that others know better... the problem of course is with the present lot they do know better but shouldn't. The architect should be the conductor of all instruments. I don't sweat wire sizes but I do sweat light fixtures and placement, I don't sweat the size of a beam but I do sweat the type of framing.... the problem is today that we've assigned all the sweat to others and wonder why we don't make any money, we wonder why people think we are not needed and wonder why everybody thinks we don't know anything.

This thing about a wall angle is simply a metaphor for what's really wrong . We've got to get back to knowing how things work, we've got to get back to conducting the instruments, we've got to get back to being leaders and not being afraid of sweat. I see a lot of "give up" in these threads.

Feb 21, 15 12:31 am  · 
 · 
slowhare414

"This thing about a wall angle is simply a metaphor for what's really wrong . We've got to get back to knowing how things work, we've got to get back to conducting the instruments, we've got to get back to being leaders and not being afraid of sweat. I see a lot of "give up" in these threads."

 

^^this...

...knowing that there is often a reason for the deck edge angle is more important for an architect than knowing the exact forces involved.  An engineer may typically run conservative and a contractor may be a great resource on the practicality of a detail, but there are enough instances where a contractor does not understand how structure works and is not capable of providing the expertise necessary to design the project.

---please, note that some particularly good contractors often can suggest very good details that are not only an adequate alternative, but that are actually better and cheaper at the same time.  Learn from them.  But do not blindly accept anything...think it through.

And not just contractors, all of the consultants...work with them and get them to explain what goes into their calcs/design considerations for any components, and how changing one thing may adversely affect something else.  Maybe they don't have the time to explain each and every one of their decisions on every job, but certainly if you have a good relationship with them and are willing to learn, it can only help the work flow if you have at least a basic idea of the types of things that have an effect on their portion of the project.

Feb 21, 15 1:25 am  · 
 · 
Olaf, slowhare, Carrera: I appreciate your patience. While we may not agree on all the particulars, I really don't think we are that far apart and probably agree on more levels than this thread probably shows.

Generally, I am not as inexperienced as my screen name would suggest. I've worked on the contracting side of this industry enough to know what the sawdust smells like in the morning (I'm partial to that from real lumber, not plywood or OSB). Also old enough to get the movie reference, but not old enough to be part of the war it came out of. Anyway, I end up doing a lot of drawing review and QA/QC as part of my regular duties at my firm. I'm the first to admit I don't know everything, but I do think I have a general grasp on a lot of the things that come across my desk. I also think I have a good sense for when I need to ask questions.

A large part of those duties is figuring out where we get ourselves into trouble and end up taking on risks and/or liability unnecessarily. The other part is helping the architects (who should really know better) understand what they've done by drawing something or more likely notating something a certain way. Some of the risk is ok, some of it might not be. But at a minimum we should at least understand when we've taken on those risks so we can decide whether or not it is worth it.

For the record, I don't think we should just leave it open for the contractor to choose. I just haven't heard the argument from what I would consider the architect's realm of responsibility on the project (except for b3ta's and maybe one other point).

Whether we as a profession want to get back to being master builders I don't think really matters at this point because clients are not generally hiring us for that. They are hiring us to fulfill what is negotiated in our agreements ... The majority of which are the AIA standards. That is what they expect and in the case of a dispute, that is what the lawyers will look at ... including the lawyers defending us. It's hard to make a case to defend us when everywhere they look we've been acting differently than what the agreement says.

P.s. If someone is willing to send me a standard agreement between owner and architect as the master builder I would be very interested in reading through it. Doesn't have to be AIA either. But I doubt the EJCDC would publish anything like that. Consensus docs maybe? Bueller?
Feb 21, 15 3:08 am  · 
 · 
Dank Gehry

what is a post about making buildings doing on an architecture forum?

Feb 21, 15 3:43 am  · 
 · 
Saint in the City

This thing about a wall angle is simply a metaphor for what's really wrong . We've got to get back to knowing how things work, we've got to get back to conducting the instruments, we've got to get back to being leaders and not being afraid of sweat. 

No offense, Carrera, but you worked pretty hard on this thread to steer away from your original premise, which was that no one should ever use steel angles to support the deck.  As several here have pointed out, there are numerous structural reasons why angles are often the necessary and superior choice.  Your premise is wrong.

Feb 21, 15 5:28 am  · 
 · 
b3tadine[sutures]

Slowhare, that's why I think in the instance detailed above, in the photos, it would seem the angle is strictly for edge support, and not diaphragm. If you look at the photo with the roof drains, the edge of deck, at the angle, appears to not have the kinds of welds I'd anticipate as part of the diaphragm. I do agree with everything else you've noted.

Feb 21, 15 7:27 am  · 
 · 
slowhare414

b3tadine,  maybe that is the case for this particular example...it is very hard to comment on the overall structural system from just a few pictures.  I just wanted bring up that an edge angle is often a part of the overall lateral force resisting system, and should only be excluded if OK'd by the engineer--but will likely cause them to create a load path in some other way and that might be much more expensive than an edge angle.--note the diagonal beams that may be there to transfer the lateral forces. 

--just a quick comment... I don't particularly care for the first detail where the joists bear on an angle bolted to the wall.  I realize that there may be situations where you are stuck and have to detail it this way, and even though the engineer might get it to 'calc-out' I don't think it is good practice.  I might not feel as strongly as Miles Jaffe, as far as a being a recipe for disaster, but I certainly understand where that comes from.
 

Feb 21, 15 8:28 am  · 
 · 
b3tadine[sutures]
Slow, completely agree. My comments were limited to the info provided, but yes.
Feb 21, 15 9:09 am  · 
 · 

Block this user


Are you sure you want to block this user and hide all related comments throughout the site?

  • ×Search in: