ARE Hotline: PDD

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Don’t wake up in a cold sweat worrying about project type analysis or requirements. Post your question in this thread for our on-call licensed experts to answer. Like all good things they take some time, but rest assured you’ll get a response within 36 hours. The expert for this division is @coachbryanhadley.

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Hi everyone! Has anyone found a good source for types of woods used for interior finishes?

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Do you mean for flooring, paneling, or casework?

Hello! Why do copings at parapets typically drain to the roof side? When is it appropriate to use a coping that drains to both sides of a wall/parapet?

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For things like doors/window frames/cabinetry- thanks for asking!

What is are the benefits of using a resilient channel vs a layer of GYP for STC ratings? It seems like they do more or less the same thing - when would you use one over the other?

Hey @rebeccaa, good question. Parapets generally drain to the roof side for a few reasons:

  • To avoid ‘raining’ on folks as they interact with the building. If the parapet drained toward the exterior wall, it could shed water onto people, or pool on the ground creating standing water, etc. This is particularly dangerous in winter months where water might freeze and cause someone to slip, injuring them.
  • Building hydrology. It’s easier to control water from one, large space (the roof) instead of controlling how water moves down exterior walls and away from the building. It is assumed that some water will infiltrate exterior walls, but we don’t want to pour buckets of water down the cavity of exterior walls, as they’re generally not built for that. Think of walls as water-resistant and roofs as waterproof.
  • Materiality. Again, it’s easier to layer up roofing behind parapets with ugly, waterproof materials to help move water off the building in a controlled way. Walls aren’t meant to hold water for extended periods of time, whereas roofs are.

Let me know if you have any follow up questions!

Thanks Cat, this makes a lot of sense.
To follow up: when would a double pitch coping be the right choice? Would this be for an exterior retaining wall, or decorative wall? I’ve been thrown off by this option on a few PDD/PPD test questions.

Hmmm. I haven’t used a double pitch parapet in practice, but I did a little research and came across this page. It seems to suggest that a double pitch coping isn’t necessarily uncommon, and would be used to achieve a desired aesthetic for the building/wall.

The page also goes into detail about how parapets help prevent roof edge lift. Take a look through and let me know if that answers your question. @Heather, do you have any further insight on copings?

I haven’t seen a listed NCARB guide for this, but in general, I go straight to manufacturers’ websites and specifications. The Architectural Woodwork Institute puts out a book called Architectural Woodwork Standards that is a very comprehensive (and unbiased) explanation of all you mention that you may find quite helpful.

The link you supplied is very informative. Thanks for sharing!

@rebeccaa I think there are a few different scenarios when the double slope would be a viable solution. In the image you show, it looks like the coping is for decorative reasons. That cap is a lot nicer looking than a piece of bent sheet metal with a drip edge.

The image you show is a concrete or stone cap, but often times, coping is made of bent sheet metal. This is extremely thin and while slick and easy for water to roll off of, if there are heavy winds that have debris land on it or wind that gets caught underneath, the metal can very easily get bent, causing a valley or bend for the water to pool in. If you intentionally bend the sheet metal, you can avoid longer and less stable spans of this.

I’d also consider the thickness of the exterior wall. Sometimes, the cap needs to slope. If you’re pressed for AHJ height restrictions, inches could make a difference. Maybe you can’t afford a 3" slope, but you can do 1.5".

Just some food for thought…

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There are so many variations of assemblies. Resilient channels have benefits. So does extra GWB. So do staggering studs. So do pulling walls all the way to the structure. There are a lot of variables. Have you seen this resource before?

http://www.usg.com/content/dam/USG_Marketing_Communications/united_states/product_promotional_materials/finished_assets/acoustical-assemblies-en-SA200.pdf

I use this a lot to check STC and UL references.

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I have a question regarding the construction document.

I am working for an architectural firm based in NYC and doing a single-family house project in NY. My current task is to do interior elevations. The senior architect recently reviewed my work and told me that I should never put the dimensions in the interior elevations for liability reasons. If the contractor spots the dimensions that are off and the problem arose because of that, he could make a claim against the architects. And he further told me that the only place we put the dimensions is the locations of outlets. Also, he also told me to avoid showing the distance whenever I can and to customize the dimension string by saying equal. For instance, if the outlet is located at the center of the room, I am supposed to put the two dimension strings saying EQL instead of showing the actual number.

-Is the senior architect correct?
-Where do we usually put the dimensions in the interior elevations?
-Is there a place where I can study the complete working drawing?

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Is there a good resource that shows where firestops belong in differnet wall types? In my research I have only seen them used in wood construction at the intersection of a wall and floor.

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Hi @Arch123, this is a good question. Liability is nuanced and with respect to annotations it depends upon the specific information you are trying to convey in your drawings. Of course you need to give enough information to the contractor to inform them of the design intent without getting your firm in trouble.

In general the senior architect is correct. Per the AIA A201 “General Conditions”, the Contractor is responsible for means and methods, sizes and quantities. However, if the Architect puts quantities or dimensions on the drawings the Architect can be held responsible if something does not work out. However, you can’t leave all the information off the drawings or the Contractor will be lost, and the owner frustrated and wondering why they hired you. What your Senior Architect should be instructing you to do is the following:

For any existing dimensions or critical dimensions where a manufacturer has specific requirements (such as inside clearances at an elevator shaft) ALWAYS instruct the Contractor to VERIFY. This can be done by adding an instruction to verify in the field: “X’-X” VIF" to verify an existing dimension, or by adding a note to “VERIFY CLEARANCES PER MANF.” In this way, you can both inform the contractor of the information they need to know while also leveraging the responsibility of verifying those dimensions.

Dimensions for interior elevations are no exception. Let’s take your example of the receptacles. Your goal is to instruct the contractor to understand your intent to center the outlets between walls, regardless of the overall length of the wall. So, if you gave the contractor an overall width of, say 10’-0", you might think you could dimension off the right side to the center of the outlet as 5’-0." Seems logical, right? However, say the wall is actually 9’-7 13/16" long. Now your 5’-0" dimension doesn’t put the outlet at the center of the wall - it would be slightly but noticeably off center. Let’s say the contractor has installed the receptacle and the wall is closed up and finished before you notice the error. Now you have the choice of asking the owner if they want to go through the trouble of undoing the work (and you will technically owe them the cost of doing so), or asking them to live with it. This is why it is good practice to give an overall wall width as X’-X" VIF and then show the dimensions to center of the fixture as “EQ” / “EQ.” Does that make sense? You will see many practical examples of this in your career and it will make more and more sense down the line.

The information you include in your interior elevation drawings will depend on the drawing set and where your firm tends to show various kinds of information. You could potentially show vertical dimensions for window sills / headers, placement of fixtures and openings such as outlets, lights, doors, windows, toilets, grab bars, etc. You might show ceiling heights and widths of rooms - it all depends on how your drawing set is set up, and if you have consultants who are showing some of this information elsewhere. One general thought on this is to always look to avoid redundancy. If you have a dimension showing the spacing of walls on a floor plan, you probably don’t need to show it again on the elevation. This is an area where we architects commonly get into trouble… because if there is an inconsistency from one to the other the contractor will pick the wrong one every time…

Last, I am unfortunately not aware of any great resources for complete working drawings. I have been thinking someone needs to author a text on the subject. Work experience is your best tool, which of course depends upon the quality of mentoring you’re getting. Never be shy to ask questions at your firm. They are investing in you and want to help you become a better architect. It helps you and them.

Hope it helps.

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Hi Rebecca, thanks for raising this question. Typically, fire-stopping is required at joints and openings in assemblies required to provide a fire resistance rating (hence why you’ve seen it used at wall / floor intersections in wood construction). Some other examples might include penetrations for pipes, conduits, ducts, cabling, and joints at intersections between walls and floors of any mix of materials required to provide a fire resistance rating. Below is an diagrammatic !example of fire stopping around a pipe penetration through a masonry horizontal assembly:

If you really want to become an expert on the subject try https://www.firestop.org/technical-library.html. They have some great resources. Here are a few to get you started:

Hope it helps.

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Is there a reliable resource out there that shows the basic MEP symbols that I can study from?

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Hi Rebecca,

Some of your confusion may stem from the tendency of different MEP engineering consulting firms to use slightly varying symbols on their drawings. For the ARE, the best resource is Wiley Publishing’s “Architectural Graphics Standards

Although expensive, it is the basis used by NCARB and is generally an indispensable resource, so may prove well worth the investment. You could also look on ebay / amazon / elsewhere for an older edition as not much has changed with respect to mechanical, electrical, and plumbing symbology.

For a free online resource, Archtoolbox.com has some nice images of common symbols.

Good luck. Hope it helps!

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