Loose Plaster Ceiling & Wall Hazards: Falling Plaster Injury Risk

Loose plaster & plaster lath - how to identify & evaluate the hazard
- Plaster System identification and history of use
- Photo guide to plaster coatings, cracks, bulges, hazards
- Plaster ceiling collapse hazards & photographs
References

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Loose or collapsing plaster ceiling hazards: here we provide a photo guide to identifying types of plaster installed in buildings, using building ceilings as a photo and investigation guide. In this article series we describe and discuss the identification and history of older interior building surface materials such plaster, plaster board, split wood lath, sawn lath, and expanded metal lath, Beaverboard, and Drywall - materials that were used to form the (usually) non-structural surface of building interior ceilings and walls.

Loose Plaster is Unsafe, Especially Loose, Falling Plaster Ceilings

Watch out: for loose plaster that can fall and injure building occupants.

If ceiling plaster is bulged and moves when you apply gentle pressure to it, chances are that the plaster keys, the protruding plaster that oozed between the plaster lath strips to mechanically secure the plaster surface in place, have broken off.

On the other hand, some "bulged"-looking plaster may be soundly secured, as we describe at PLASTER BULGES & PILLOWS.

Wood Lath Ceiling Collapse Photographs

Our loose plaster photo at below left shows wall plaster that was quite loose and whose plaster ears had broken away. Some renovators use the term "rotted plaster" or "rotten plaster" but of course since we're talking about a cementious material, not organic wood, "rot" is a euphemism for deteriorated.

Our loose plaster ceiling photo (below right) shows an unsafe building ceiling at risk of falling.

Plaster in this condition can easily fall away. While small areas of loose plaster can be successfully re-adhered using plaster washers and screws, a better (but more costly) repair is to remove the loose plaster entirely and re-plaster the section properly.

At below are two photographs of plaster ceilings in the attic that has already fallen away in two older homes. You may also enjoy noticing the pit-sawn kerf marks on some of the plaster lath of this older home in the photo at below left, and the hand-wrought iron hook in the photo at right. .

Watch out: often the framing supporting plaster ceilings in homes built before 1900 was sized to be just strong enough to support the weight of the plaster itself. Such ceiling structures were not intended to support the weight of a curious home owner or home inspector.

Expanded Metal Lath Plaster Ceiling Catastrophic Collapse Case

Plaster ceilings in newer buildings are not immune from collapse either, as you'll see by the catastrophic ceiling collapse shown just below. This plaster ceiling was applied on expanded metal lath. The lath was wired to steel pipes or bars that in turn were hung from a smaller number of steel supports. The final steel supports were hung from wire ties connected to fasteners that had been "pin-shot fasteners" shot into the sides of concrete ceiling joists.

The combination of several factors led to this ceiling collapse:

An insufficient number of fasteners was used to secure the whole suspended ceiling structure to the concrete beams above - considerably less than called for the industry standards including those of the Hilti Corporation, a producer of pin shot fasteners. This was the most apparent and most significant cause of this ceiling collapse in our opinion.
The pin shot fasteners used as ceiling hangers may have been of the wrong type for this application and may have been improperly loaded.
It is possible that the shot fasteners used to provide fasteners for the wire hangers supporting the ceiling were not properly installed, allowing some of them to separate from the concrete. For example if pins were shot directly "up" into the underside of joists or beams when they were intended to be shot into beam or joist sides, they may have lacked sufficient friction to remain in place, being later pulled out from the downward force of the weight of the ceiling.
There was no perimeter support for the ceiling.
We considered the possibility that damp conditions in the building may have contributed to fastener loosening or deterioration, but the absence of rust in the field photos argues against that factor.
Nearby demolition for building renovation work created vibrations sped or precipitated this collapse that could have occurred at any time.

Typical Design & Construction of Suspended Plaster Ceilings

According to Van Den Branden and Hartsell, a typical suspended wire-mesh based plaster ceilings using hangers, carriers, and furring channels (such as described by Inland Steel Products Co.,) typically used No. 8 galvanized wire, though other wire sizes, rods, and flat iron were also used:

#8 galvanized wire. Wire in gauges 12,10, 9, 8, 7, and 6 sizes. Common #8 steel wire is rated to carry 16 sq.ft. of completed ceiling per hanger (presuming that the ceiling weight and thickness are also to standard specifications).
3/16" pencil rod suspended ceiling hangers
1" x 3/16" flat iron suspended ceiling hangers

Fasteners for suspended plaster ceilings: None of VanDenBranden/Hartsell's hanger examples included pin-shot fasteners, though that may be due to the age of the text. They describe

Hangers attached to concrete slabs (overhead ceilings) by looping and embedding wire in the concrete (obviously installed during original construction)
Securing suspended ceiling hangers to inserts cast into the concrete
Suspended from wood joists by drilling holes 3" or more above the joist bottom
Suspended from wood joists by nailing 16d spikes through the joist [center]

Also see BUILDING SAFETY HAZARDS GUIDE for more building hazards of particular concern to homeowners or building contractors, building inspectors, and home inspectors.

Frequently Asked Questions (FAQs) about plaster ceiling collapses, falls, injuries, cause, prediction, prevention

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Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

America's Favorite Homes, mail-order catalogues as a guide to popular early 20th-century houses, Robert Schweitzer, Michael W.R. Davis, 1990, Wayne State University Press ISBN 0814320066 (may be available from Wayne State University Press)
Asbestos products and their history and use in various building materials such as asphalt and vinyl flooring includes discussion which draws on Asbestos, Its Industrial Applications, D.V. Rosato, engineering consultant, Newton, MA, Reinhold Publishing, 1959 Library of Congress Catalog Card No.: 59-12535 (out of print).
ASHI, American Society of Home Inspectors,® Inc., 932 Lee Street, Suite 101, Des Plaines, Illinois, 60016. The American Society of Home Inspectors is the first and leading national association of home inspectors in the U.S. Website: www.ashi.org
ASTM C 842
ASTM C 841 Metal Lath or gypsum lath installation
Building Research Council, BRC, nee Small Homes Council, SHC, School of Architecture, University of Illinois at Urbana-Champaign, brc.arch.uiuc.edu. "The Small Homes Council (our original name) was organized in 1944 during the war at the request of the President of the University of Illinois to consider the role of the university in meeting the demand for housing in the United States. Soldiers would be coming home after the war and would be needing good low-cost housing. ... In 1993, the Council became part of the School of Architecture, and since then has been known as the School of Architecture-Building Research Council. ... The Council's researchers answered many critical questions that would affect the quality of the nation's housing stock.
- How could homes be designed and built more efficiently?
- What kinds of construction and production techniques worked well and which did not?
- How did people use different kinds of spaces in their homes?
- What roles did community planning, zoning, and interior design play in how neighborhoods worked?
"
Isham: "An Example of Colonial Paneling", Norman Morrison Isham, The Metropolitan Museum of Art Bulletin, Vol. 6, No. 5 (May, 1911), pp. 112-116, available by JSTOR.
Plastering, PM 5, Product & Systems Technology, US Gypsum, May 1998, web search 10.5.2010, original source: http://www.usg.com/rc/technical-articles/plaster/
plastering-technical-guide-veneer-plaster-joint-reinforcement-systems-en-PM5.pdf
United States Gypsum Company, 125 South Franklin ST., PO Box 806278, Chicago, IL 60680-4124,
Paraphrasing from this document: USG uses the term shadowing in this document in describing the visual effect over gypsum board joints caused by the lower moisture absorption rate (take-up) and lower capacity than gypsum base face paper. Shadowing at joints occurs where veneer plaster is applied over tape joints, requiring a second coat to completely hide the tape, providing a visually uniform surface. USG Advises: "This [second] cover coat must be allowed to harden and dry before plaster application is started.
Gypsum Construction Handbook [purchase at Amazon.com] H17, Technical Folder SA920 and PM2, PM3 and PM4, United States Gypsum Company, 125 South Franklin ST., PO Box 806278, Chicago, IL 60680-4124,
Plastering Skills, F. Van Den Branden, Thomas L. Hartsell, Amer Technical Pub (July 1, 1985), ISBN-10: 0826906575, ISBN-13: 978-0826906571 [purchase at Amazon.com]
Gypsum Construction Guide, National Gypsum Corporation
Metal Lath Specifications, Specification for metal lath and accessories, Lath and Plaster from Amico, a lath and plaster accessory producer.
Lath & Plaster Systems, 092300/NGC, National Gypsum Lath and Plaster Systems, National Gypsum Corporation, 800-628-4662 describing National Gypsum's Kal-Kore brand plaster base
Gypsum Construction Guide, National Gypsum Corporation, 2001 Rexford Road, Charlotte, North Carolina 28211, Tel: 704-365-7300, Email: ng@nationalgypsum.com, Website: http://www.nationalgypsum.com
MSDS: Gold Bond® brand gypsum board products, plaster base, National Gypsum Corporation. Other drywall MSDS sheets are found at Drywall MSDS.
Metal Lath Specifications, Specification for metal lath and accessories, Lath and Plaster from Amico, 3245 Fayette Ave. P.O. Box 3928, Birmingham, AL 35208, (205) 787-2611, (800) 366-2642 and in Canada: 1080 Corporate Drive, Burlington, Ontario L7L 5R6, Canada, (905) 335-4474, (800) 663-4474. Amico is the largest metal lath producer in North America. Website: http://amico-lath.com/
Weaver: Beaver Board and Upson Board: Beaver Board and Upson Board: History and Conservation of Early Wallboard, Shelby Weaver, APT Bulletin, Vol. 28, No. 2/3 (1997), pp. 71-78, Association for Preservation Technology International (APT), available online at JSTOR.
Gypsum Construction Guide, National Gypsum Corporation
Gypsum Construction Handbook [purchase at Amazon.com] H17, Technical Folder SA920 and PM2, PM3 and PM4, United States Gypsum Company, 125 South Franklin ST., PO Box 806278, Chicago, IL 60680-4124,
Plastering, PM 5, Product & Systems Technology, US Gypsum, May 1998, web search 10.5.2010, original source: http://www.usg.com/rc/technical-articles/plaster/
plastering-technical-guide-veneer-plaster-joint-reinforcement-systems-en-PM5.pdf
United States Gypsum Company, 125 South Franklin ST., PO Box 806278, Chicago, IL 60680-4124,
Paraphrasing from this document: USG uses the term shadowing in this document in describing the visual effect over gypsum board joints caused by the lower moisture absorption rate (take-up) and lower capacity than gypsum base face paper. Shadowing at joints occurs where veneer plaster is applied over tape joints, requiring a second coat to completely hide the tape, providing a visually uniform surface. USG Advises: "This [second] cover coat must be allowed to harden and dry before plaster application is started.
What Style Is It?: A Guide to American Architecture, Rev., John C. Poppeliers, S. Allen Chambers, Wiley; Rev Sub edition (October 6, 2003), ISBN-10: 0471250368, ISBN-13: 978-0471250364
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The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.

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American Plywood Association, APA, "Portland Manufacturing Company, No. 1, a series of monographs on the history of plywood manufacturing",Plywood Pioneers Association, 31 March, 1967, www.apawood.org
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