WEBSTER ELEMENTARY SCHOOL New Rochelle, New York Evaluation of Collapsed Ceiling Room 204 Structural Inspection Report Client: CSArch Architecture Engineering Construction Management 19 Front Street, Newburgh, NY 12550 WARNING: The alteration of this material in any way, unless under the direction of a comparable professional, i.e. a Professional Engineer, is a violation of the New York State Education Law and/or Regulations and is a Class A misdemeanor. 80 Wolf Road Suite 300, Albany, NY 12205 518.453.9431 gpinet.com
T a b l e o f C o n t e n t s T a b l e o f C o n t e n t s... 2 1.0 Abstract... 3 2.0 Background... 3 3.0 Observations... 3 4.0 Findings... 5 5.0 Recommendations... 7 6.0 Photo Log... 8 Appendices... 15 p a g e 2
1.0 Abstract Thomas Ritzenthaler, A.I.A. of CSArch contacted GPI on the afternoon of August 5, 2015 following the report of a ceiling collapse at the Daniel Webster Elementary School located at 95 Glenmore Drive. GPI was informed by CSArch that the debris had been cleared of Asbestos Containing Materials and that the electrical power to the room had been terminated. GPI was provided a copy of the 2010-2011 Building Condition Survey (BCS) report and was asked to conduct an emergency site assessment to inspect the collapse zone and other suspect ceiling areas on the second floor of the building. GPI structural engineers John G. Rizzo, P.E. and Kelly S. Phillips performed the emergency structural inspection on August 5, 2015 from 7:30pm to 8:45pm while escorted by the school s Head Custodian. This report will present GPI s observations, findings and recommendations. 2.0 Background The building, constructed in 1930, is a stone masonry, reinforced concrete and wood-framed, threestory structure having a gross square footage of 70,831, of which approximately 32,000 sf is for instructional classrooms of 538 registered K-5 students in 2005. The roofing system is a combination of gable roofs with slate shingles and a flat roof with rubber roofing membrane. The 2010-2011 BCS reported evidence of water penetrations and active leaks in the roofing system as well as roofing failures/splits/cracks/rot/decay/corrosion with an estimated remaining life of 1 year. The BCS also estimated the remaining life of the ceiling systems at 5 years. It is unknown whether the estimate of remaining life of the ceiling systems was in reference to the suspended acoustic ceiling tile system or the originally constructed plaster ceiling above. To date, GPI has not reviewed original construction documents or construction documents for previous renovations to the building. We are also of the understanding that there is no reported history of plaster ceiling failures at the school. 3.0 Observations During GPI s inspection of Room 204 and the plenum space between the suspended and plaster ceiling of Rooms 203, 201 and the second floor corridor, GPI engineers made the following observations: Room 204 o A global failure of the room s ceiling system has occurred revealing the existing wood ceiling joists, which are suspended from the wood roof joists and supported on the exterior wall and interior hallway wall. The collapsed ceiling has also caused a failure of plaster wall finishes along the north, south and east walls extending approximately 2 below the corner of the ceiling (see photos 1-4); p a g e 3
Room 203 o The debris contained suspended acoustic ceiling tile and metal track system elements, metal lath and plaster, loose filled fiberglass insulation, HVAC metal ductwork, recessed electrical lighting fixtures, electrical wiring and various other building systems. There was no evidence of attic-stored materials atop the debris pile; o The suspended ceiling tile system was anchored to the original plaster ceiling system using threaded toggle bolts spaced between the ceiling joists (see photos 5 & 6); o The plaster ceiling/metal lath system is approximately 1 ¼ to 1 ½ thick with a thicker architectural crown detail around the perimeter of the ceiling; o The plaster ceiling system was attached to the wood ceiling joists with 1, blued nails with 3/8 diameter heads. The nail spacing varied from 4 ¼ (min) to 11 (max), with the majority of nails spaced between 5 ¼ and 6 ¾. Nearly every nail has been stripped from the supporting ceiling joists (see photo 4). Approximately 25% to 33% of the nail fasteners over approximately 4 of joist length had pulled the heads of the nails though the metal lath grid opening and were missing from the intact plaster debris as observed along two ceiling joist lines at the southeast corner of the debris pile (see photos 5 & 6). The nails observed during our inspection had minor corrosion on the shank and underside of the nail head while the metal lath showed signs of localized corrosion at some of the nail locations. We noted that the nail head could easily be removed from the metal lath since the diameter of the nail head was within a 1/16 of the size of the metal lath grid opening; o Approximately 4 to 5 of loose, fiberglass insulation was placed between the ceiling joists atop the plaster. The insulation debris appeared dry and loose; o Mechanical ductwork could be seen within the debris pile between the acoustic tile ceiling material and the plaster ceiling debris along the east wall; o Electrical wires were hanging from the ceiling joists to the debris across the room. o Located across the hall from Room 204, the ceiling construction consisted of the original plaster ceiling with a suspended acoustic ceiling tile system. The suspended ceiling system included recessed fluorescent lighting fixtures (2 x4 ) and was supported by threaded toggle bolts and hanger wire attached to the original plaster ceiling. Remnants of adhesive used to attach acoustic ceiling tiles to the plaster ceiling existed across the entire ceiling (see photos 7 & 8); o The plaster ceiling system showed signs of significant localized water damage. An area of 24 sf over the entry door area to the room and towards the south wall of the room had dropped and was hanging as result of water damage (see photo 7). p a g e 4
Room 201 o Located north of Room 203, the ceiling construction consisted of the original plaster ceiling with a suspended acoustic ceiling tile system. The suspended ceiling system included recessed fluorescent lighting fixtures (2 x4 ) and was supported by threaded toggle bolts and hanger wire attached to the original plaster ceiling. Remnants of adhesive used to attach acoustic ceiling tiles to the plaster ceiling existed across the entire ceiling (see photos 9 & 10); o The plaster ceiling system showed signs of significant localized water damage in multiple locations. An area of 25 sf over the entry door area to the room and towards the south wall of the room had dropped and was hanging as result of water infiltration. There was also an area of 75 sf towards the middle of the room that had been damaged by water infiltration (see photos 9 & 10). North/South Hallway (2 nd Floor) o The hallway ceiling construction was similar to that of the rooms inspected on the second floor, except that the adhered acoustic ceiling tiles remained attached to the original plaster ceiling finish. The space between the suspended ceiling and the plaster ceiling was congested with HVAC metal ductwork and electrical wiring systems (see photos 11 & 12). First Floor Ceiling ( 2 nd Floor Framing) o Following our site inspection, GPI was provided with information regarding the second floor and first floor ceiling systems. The second floor framing consists of reinforced concrete floor slabs and reinforced concrete beams that support an original plaster and metal lath system from which a suspended acoustic ceiling system, HVAC ductwork, lighting and electrical infrastructure was later attached. Similar to the ceiling alterations performed on the second floor, the additional dead loads of these elements is being carried directly by the plaster and metal lath ceiling system and then transferred to the reinforced concrete beams, making the critical element the connection between the wire lath and the concrete beam (see photo 13). 4.0 Findings Collapse of the ceiling in Room 204 appears to be a classic case of load transfer resulting in the progressive collapse of the entire system. Localized failure of individual fasteners result in direct load transfer to the adjacent fasteners, increasing the tension stress to a point where those fasteners fail or pull out of the supporting wood ceiling joists and then transfer load to the next adjacent set of fasteners. Ultimately, in these situations, the load transfer becomes so great in magnitude that an p a g e 5
abrupt, catastrophic collapse of the entire system will occur. Based on our initial field inspection and observations, our preliminary assessment of events leading to the collapse included the following: The 1941 Architectural Graphics Standards, 3 rd Edition specified both Nailed-on or Tied and Nailed Metal Lath and Plaster Ceilings for wood construction. The lath is fastened with 6d common nails, 1 ¼ roofing nails or 1 staples spaced 6 O.C. In the Nailed and Tied configuration, the metal lath is fastened with 6d nails spaced 6 O.C. and double loops of tie wire spaced 24 to 27 along alternate ceiling joists that were supported by a 16d nail driven through or 2-8d nails driven on each side of the supporting ceiling joist (see Appendix A). The 1951 Architectural Graphic Standards, 4 th Edition, calls for Tied and Nailed Metal Lath and Plaster Ceilings for wood construction. The metal lath was to be attached using 1 ½ Barbed Roofing Nails with 7/16 heads spaced at 6 O.C. The metal lath is also supported using a 16d nail driven through or 2-8d, one on each side of the supporting ceiling joist from which a double loop of tie wire, spaced at 24 to 27 along alternate ceiling joists, would have been looped and threaded through the metal lath. This type of nailed and tied construction was typical for buildings subject to more than ordinary vibration (schools, etc.). Our inspection uncovered 1 blued nails with 3/8 diameter heads used in the ceiling construction, however, there was no evidence of the tie wires suspended from driven nails in the ceiling joists being used (see Appendix B). Today, the National Association of Architectural Metal Manufacturers, specifies a similar attachment detail of 7/16 diameter, barbed roofing nails with double loops of hanger wire suspended from a 16d nail or 2-8d nails (see Appendix C); The addition of an adhered acoustic tile system, suspended acoustic tile ceiling system, HVAC metal ductwork, fluorescent lighting, electric wiring systems and fiberglass insulation has significantly increased the dead load on the original plaster ceiling system, ceiling joist and roof joists. This increased loading has increased the tensile stress on the nail fasteners that attach the plaster ceiling system to the supporting wood ceiling joists; The suspended ceiling system, attached using toggle bolts to the supporting plaster ceiling, is utilizing the plaster ceiling system as a load path to the supporting nail fasteners that attach the metal lath to the ceiling joists. To avoid this condition, the suspended ceiling system should have been attached directly to the supporting ceiling joists. Direct attachment would not have increased the load on the plaster ceiling system or the nail fasteners; Water infiltration from the failed roof system has saturated and softened the plaster ceiling materials causing a localized load increases and material damage. The increased load can result in nail heads pulling through the metal lath grid due to the minimal engagement of the nail head and metal lath grid or progressive pullout of the nail from the supporting wood ceiling joist, ultimately resulting in load transfer to adjacent nail fasteners. p a g e 6
5.0 Recommendations At this time, we deem the current condition of the building s ceiling system to be UNSAFE and a threat to public safety. We recommend that access to the building be restricted to authorized personnel only. It is our opinion that the remaining ceilings of the second floor have the potential of similar abrupt, catastrophic collapse given the perceived errors/omissions in construction (undersized nails and lack of ties), 80 years of building vibrations, water damage and significant load increase on the plaster ceiling and nail fasteners. We also view the first floor ceilings to also present a collapse potential given the apparent improper post construction loading of the plaster ceiling through the addition of a suspended ceiling system, mechanical ductwork and electrical systems. We recommend that until a time when a comprehensive investigation/inventory of the entire school ceiling systems is completed, and a course of corrective action has been identified, that the building remain unoccupied with restricted access. Should you have any questions regarding this report, please feel free to contact our office. Sincerely, John G. Rizzo, P.E. Assistant Vice President / Building Systems Department Manager p a g e 7
6.0 Photo Log Photo 1 Room 204 (looking south) Photo 2 Room 204 (looking north) p a g e 8
Photo 3 Room 204 Ceiling Joists / Roof Joists Photo 4 Room 204 Ceiling Joists / Roof Joists p a g e 9
Photo 5 Room 204 Plaster, Metal Lath, Nails and Toggle Bolt Photo 6 Room 204 Plaster, Metal Lath, Nails and Toggle Bolt p a g e 10
Photo 7 Room 203 Failing Plaster Ceiling System ( 24 sf) Photo 8 Room 203 Toggle Bolts Supporting Suspended Ceiling System p a g e 11
Photo 9 Room 201 Failing Plaster Ceiling System ( 25 sf) Photo 10 Room 201 Failing Plaster Ceiling System ( 75 sf) p a g e 12
Photo 11 2 nd Floor Corridor Ceiling Space (looking east) Photo 12 2 nd Floor Corridor Ceiling Space (looking south) p a g e 13
Photo 13 2 nd Floor Framing with attached 1 st Floor plaster ceiling p a g e 14
Appendices Appendix A:... 1941 Architectural Graphic Standards, 3 rd Edition (pp. 16) Appendix B:... 1952 Architectural Graphics Standards, 4 th Edition (pp. 24) Appendix C... Guide Specification for Expanded Metal Lathing and Furring (pp. 30) p a g e 15
Appendix A p a g e 16
Appendix B p a g e 24
Appendix C p a g e 30
T e a m w o r k Q u a l i t y C o m m i t m e n t