What is the name and history of this unusual structural metal roof deck?
May 3, 2021 8:23 PM   Subscribe

A recent renovation of a small local building uncovered an unusual structural metal roof deck that no one has been able to identify for me. The deck is sinusoidal in shape, with flutes about 1 foot on center, and with a depth of around 3 or 4 inches. Panels are about 3 feet wide.

The renovation contractor thinks this building was built in the 50's or 60's and that the roof deck might have been part of a kit used to construct small commercial buildings. Current manufacturer catalogs contain nothing like this. The Steel Deck Institute could not identify the deck, and their enquiries to the Metal Building Manufacturers Association and the Metal Construction Association also produced no answers. Any ideas on other possible sources of information?
posted by Jackson to Technology (11 answers total)
Can’t really tell from the picture, but is it different from regular corrugated metal roofing?
posted by hwyengr at 8:38 PM on May 3 [3 favorites]

I'm frankly surprised that the SDI didn't have anything.

If it was a "kit" type building they may be hosed; there were a bunch of no-name manufacturers popping up from circa 1950-70 doing small commercial structures, and most of them lived and died without anyone "serious" even noticing they existed in the first place.

Alas, the main guy I knew for this sort of thing has died (alas again), but you could try the CFSEI even though it's not really their specific domain. A longer shot would be the appropriate forum on Eng-Tips, but I suspect you may end up having to derive the properties from first principles using modern approaches.

...a very long shot would be the AISC, even though they don't normally cover historic steel deck, and they super-don't-cover roof deck in any form (they're "structural" steel, meaning W sections and the like) but they do have a research library going back reasonably far. I got some stuff on old Carnegie stamped-steel plates thanks to them -- I don't know who works over there any longer, so I don't know how motivated they are by cool puzzles. Time was they'd help you out, but the current staff may not be quite so driven by obscure history.
posted by aramaic at 8:58 PM on May 3 [5 favorites]

(also, if you pursue CFSEI, AISC or Eng-Tips, make sure to mention the orgs you've already contacted or literally 9/10 responses will tell you to ask the SDI etc.)
posted by aramaic at 9:02 PM on May 3 [1 favorite]

(also, the more direct measurements you can get the better; send someone up there with some digital calipers and measure the hell out of the profile)
posted by aramaic at 9:04 PM on May 3 [1 favorite]

It looks a bit like 'tray deck' but used as a roof - is this the underside of the roof or the lower skin of a membrane roof? Tray deck is usually used as a form for poured concrete floors, I can imagine it used as roofing but it'd be $.

Can you get a micrometre in to measure its thickness, coz that may be a big help towards ID.
posted by unearthed at 10:41 PM on May 3 [3 favorites]

It is a tray deck, as unearthed has mentioned. It is not the upermost roof layer unless the wiring for the lights is run on the exterior of the building (not likely). It is not uncommon to have a poured concrete roof, and this is the underside of said roof. Think of it as the mold that the concrete is poured onto.
posted by wile e at 10:56 PM on May 3 [4 favorites]

Whoever paid to have the structure built originally would have had to file plans with the town and probably even have a professional engineer do a detailed analysis to certify it as safe. You would learn quite a bit about the structure, materials/ manufacturers, and contractors if all that paperwork can be found in the town archives.

An engineering analysis would have required quite a lot of detail about that corrugated steel component, including dimensional drawings, type of steel, and any treatments, platings, and coatings applied.
posted by ZenMasterThis at 4:10 AM on May 4

In bridge engineering, we call something like that a "stay-in-place" form. Concrete is then poured on top of it to form the driving surface.
posted by dforemsky at 5:29 AM on May 4

Here this is known generically as Q decking (even though actual Q Decking hasn't been made in decades) and is used extensively for roof surfaces (both bare and as a base for rigid insulation covered by a membrane) and concrete suspended floors. You can see in my link that both the actual Q Decking and the modern variant have a version that has 3" deep corrigations 12" on center.

We've got snow loads though that may make this cost effective verses less frozen water places.
posted by Mitheral at 6:55 AM on May 4

This may be a weird lead, but the Trachte Corporation built a lot of kit commercial buildings, and while this style of deck isn't something they would have done, they have a 100-year history and may be able to dig up some institutional memory on competitor styles and designs.
posted by rocketman at 7:13 AM on May 4

Random additional thought: if the building is framed using steel joists for the roof, you should be able to locate the joist tags (err, assuming someone in the intervening years hasn't been a giant jackhole and removed them). With that information you can identify the joist, and the joist manufacturer -- which should substantially simplify locating the deck manufacturer (and, thus, the name to look for in old properties tables).

The SJI has a service to identify old joists.

...all of the foregoing is moot if the building doesn't use steel joists, of course.
posted by aramaic at 8:03 AM on May 4

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