Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

RE: Insulrock diaphragm

[Subject Prev][Subject Next][Thread Prev][Thread Next]

Yes. Many of these systems were also used on Glulams. The plank gypsum and Tectum systems were commonly used on Glulams. A lot of glulam systems have too much slope for the cast gypsum, but the plank systems were either gongue and grooved, were screwed directly to the purlins, or had special attachment clips.

Harold Sprague

From: "Eli Grassley" <elig(--nospam--at)>
Reply-To: <seaint(--nospam--at)>
To: <seaint(--nospam--at)>
Subject: RE: Insulrock diaphragm
Date: Mon, 3 Jan 2005 15:50:20 -0800

Harold -
This has been some extremely timely information for myself - thank you!  I
just happen to be getting started on a seismic investigation for a 1960 era
classroom building that has some type of "3-inch insulated slab" roof that
sounds suspiciously like what you described.  Only the system in my case is
supported by Glulam purlins.

Were there systems similar to Pyrofill that could have been designed with
Glulam purlins instead of WF?  I have an old Pyrofill technical report that
I'm using as a starting point.

Eli Grassley
PSM Engineers
Seattle, WA

-----Original Message-----
From: Harold Sprague [mailto:spraguehope(--nospam--at)]
Sent: Monday, January 03, 2005 9:55 AM
To: seaint(--nospam--at)
Subject: RE: Insulrock diaphragm


This appears to be a gypsum roof deck system. There were many manufacturers

of gypsum systems in the 1960's. The particular system that was used varied

region to region. My advice would be to find an old ICBO Research Report on

Insulrock.  I have an old US Gypsum Research Report on Thermofill and
Pyrofill.  Generally the gypsum formboards were just there to support the
cast in place gypsum, and contributed little to the strength of the
diaphragm system.  What you are referring to were often called "form
boards".  The sequence of construction for the gypsum structural deck
consisted of:
1.  The bulb tee or truss tee's were welded to the structural steel
2.  The form boards were placed on the bulb / truss tees (The form boards
were held back from the tees to allow the cast in place gypsum to flow
around the exposed portion of the tee's)
3.  Wire mesh was placed on the form board and tee's.
4.  Gypsum concrete was placed on the deck system.

The system worked pretty well unless you got a leak in the roofing system.

Allowable shear loads ranged from 510 to 1200 pounds per lineal foot.

Harold Sprague

>From: "Will H" <haynewp(--nospam--at)>
>Reply-To: <seaint(--nospam--at)>
>To: seaint(--nospam--at)
>Subject: Insulrock diaphragm
>Date: Mon, 03 Jan 2005 10:22:49 -0500
>I have an existing building from the 1960's that used Insulrock roof panels

>on bulb tee purlins. I don't see how this can be considered a structural
>diaphragm, but it is the only thing that has been distributing the lateral
>loads on the building for 40 years.
>Does anyone have any experience with this product? By looking at the
>document below, I think the planks are only resting on the tees and clipped

>to the main steel beams but the drawings don't specify.
>thanks for any help
>Will Haynes, P.E.

Don?t just search. Find. Check out the new MSN Search!

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at:
* * This email was sent to you via Structural Engineers * Association of Southern California (SEAOSC) server. To * subscribe (no fee) or UnSubscribe, please go to:
* Questions to seaint-ad(--nospam--at) Remember, any email you * send to the list is public domain and may be re-posted * without your permission. Make sure you visit our web * site at: ******* ****** ****** ****** ******* ****** ****** ********