Fire spread along the upper portions of the southwest facing exterior facade(s) of the 32-story Monte Carlo Hotel and Casino in Las Vegas, Nevada. The flames and heat caused several windows to break, but automatic sprinklers kept the fire from entering the building. It took the determined suppression crews to stop the fires progression. This article addresses the ensuing forensics investigation, contributing aspects, lessons learned and whether these combustible exterior faades should continue to be allowed.
Just before 11 a.m. on Friday, Jan. 25, 2008, the Clark County Fire Department was notified that the exterior faade of the Monte Carlo Hotel tower was burning. For more than an hour, the fire continued to propagate across the exterior, both horizontally and vertically. The fire also spread downward in some areas due to burning material falling down from the area of origin, landing on horizontal ledges below.
Heat from the flames broke out several windows and the fire attempted to gain access into the interior of the high-rise tower guestrooms, but automatic sprinklers halted its interior spread (Figure 1). In all, 17 sprinklers activated.
In addition to the Clark County Fire Department, other local jurisdictions provided mutual aid. Approximately 100 suppression personnel responded. It took the determined emergency responders using hose lines from window openings and the roof to halt the fires propagation and extinguish the burning exterior facade.
Ignition of the exterior wall was attributed to welding on a catwalk on the roof parapet wall - a 30 ft. (9 m) high screen wall. While a cause and origin investigation was begun, the results were never summarized and published. The exterior cladding materials first ignited on the left side (as viewed from the exterior) of the central core area. The fire then progressed laterally. The adjacent materials on the right side of central core faade began to burn and the fire continued to propagate laterally over these decorative materials. The fire also moved to the left along the upper portion of the west tower and began to involve the cladding materials. Over time, the fire on the west tower moved laterally approximately 80 ft. (24 m).
Once the fire progressed away from the central core area, it appeared that the decorative band at the top of the 32nd floor, the medallions between the windows on the 32nd floor and the decorative band at the top of the wall were the primary mode of lateral flame propagation. Not only did these areas exhibit their own flame-spread, the resultant flames caused the flat area of the wall above to ignite.
The fire on the exterior faade was extinguished by the emergency responders at approximately 12:15 p.m.
The 32-story Monte Carlo Hotel and Casino was constructed in 1994 and 1995. The code of record was the 1991 Edition of the Uniform Building Code (UBC).1
The plan layout of the hotel was a center tower from which three wings, each approximately 240 ft. (73 m) long, extended.
The code of record required Type I noncombustible construction. The UBC required that, for this type of building construction, the exterior walls be of noncombustible construction.
Based on information obtained by Clark County Department of Development Services, the exterior wall cladding of the Monte Carlo was an Exterior Insulation and Finish System (EIFS) that was installed at the time of construction. Additionally, it appeared that several decorative architectural details were also installed on the exterior wall at the time of construction.
UBC Section 1713 (e) 2.B allowed EIFS to be applied as exterior wall cladding. Other types of foam plastic materials would be allowed, provided they also met Section 1713 (e) 2.B.
EIFS, when applied as an exterior wall cladding, has the following components (Figure 2):
- Substrate wall system,
- Adhesive that attaches the expanded polystyrene foam plastic insulation (EPS) to the substrate wall,
- EPS insulation board,
- Glass fiber reinforcing mesh,
- Base coat on the face of the EPS that embeds the mesh and
- Finish coat.
All of these components must be present for the wall cladding to be considered a properly installed EIFS. Each component must be installed per the manufacturers recommendations and their evaluation report for the specific system.
After the fire, several questions were raised concerning the construction of the exterior faade. Hughes Associates (HAI) was asked to assist CCBD during the investigation. The primary questions concerned the installation of the EIFS, as well as potential non-EIFS materials. The questions included:
- Were the materials installed in accordance with code, the tested assemblies and the manufacturers guidelines?
- If so, were the code requirements, associated tests and manufacturers guidelines adequate?
- If not, to what extent do these need to be revised?
A few days after the fire, CCBD personnel obtained undamaged samples from the west wing of the exterior faade. Figure 3 shows the approximate locations where the various samples were removed. Samples included portions of the:
- Horizontal band at the top of the exterior wall,
- Horizontal band above the uppermost guest rooms (32nd floor),
- Horizontal band at the 32nd floor,
- Horizontal band at the 29th floor (Figure 4),
- Decorative column pop-outs that extended from the 29th floor to the 32nd floor,
- Base wall assembly of the upper screen wall, and
- Base wall assembly intended to represent the primary exterior wall covering.
The samples were inspected and descriptions were developed by CCBD and HAI personnel. During inspection of the materials removed from the Monte Carlo, smaller samples were removed and subsequently sent by CCBD to a laboratory for qualitative characterization.
It should be noted that the samples taken were taken from the west faade, near the burned area. Samples were not taken from other areas of the building and the sampling did not necessarily evaluate construction methods.
The following summary of the various materials installed on the exterior faade is based on visual observations and the laboratory analysis:
- The horizontal band at the top of the exterior wall was over 5 ft. (1.5 m) high and contained an expanded polystyrene (EPS) foam plastic core covered with a rigid non-EIFS coating.
- The horizontal band above the uppermost guestrooms (32nd floor) was approximately 6 ft. (1.8 m) high and contained up to 3 ft. (0.9 m) thick EPS foam plastic at the upper portion covered with a polyurethane encapsulant.
- The horizontal band at the 32nd floor was primarily hollow with a in. (13 mm) thick outer shell comprised of fiberglass and a gypsum-plaster binder.
- The horizontal band at the 29th floor was approximately 3 ft. (0.9 m) high and contained 2 ft. (0.6 m) thick EPS foam plastic at the top covered with a rigid non-EIFS encapsulant.
- The decorative columns between the 29th and 32nd floors were approximately 2 ft. 4 in. (0.7 m) wide and 6 in. (150 mm) thick with an EPS foam plastic core and an EIFS coating (thinner than required).
- Each of the two base wall assemblies sampled contained 5/8in. (16 mm) thick gypsum wall board covered with one inch of EPS foam. The primary difference between the two was that the EIFS coating from the upper sample was noticeably thinner but in both samples, the EIFS coating was thinner than required.
Based on the information obtained, the following findings were developed:
- The Monte Carlo had, as its exterior wall cladding in the fire area, had the following two components:
- An EIFS system that was installed in the flat areas of the building and on the decorative column pop-outs that extended from the 29th floor to the 32nd floor - the analysis indicated that these EIFS areas had a non-complying thickness of lamina (the exterior encapsulant).
- Decorative non-EIFS materials used for ornamentation - These items included the horizontal band at the 29th floor, the horizontal band at the top of the 32nd floor, the railing at the top of the parapet wall and are believed to include the medallions between the windows on the 32nd floor.
- It appears that the EIFS, when properly applied, did meet the requirements of the 1991 UBC.
- Based on the analysis of the samples, it appears that the EIFS lamina did not have the correct thickness. The actual lamina varied in thickness from approximately 28 to 69 percent less than the nominal minimum thickness.
- The EIFS had additional decorative components applied to it. These were large shapes that contained significant thicknesses of EPS and these components were not covered with EIFS lamina. The analysis concluded that they did not meet the requirements of the 1991 UBC.
- The primary contributor to the progression of the fire was the combination of materials in the decorative band at the top of the wall, the decorative band at the top of the 32nd floor (EPS with a polyurethane resin coating) and the undetermined materials in the medallions.
- Flaming droplets and burning pieces of EPS and/or polyurethane caused ignition of the large decorative band at the 29th floor. This decorative band was composed of EPS and had anon-EIFS coating.
- EIFS in the flat portion of the parapet wall was involved in the fire but was not the primary contributor to the lateral propagation of the fire, even though it appears to have a non-complying thickness of lamina. It did burn in the immediate area of fire exposure, as would be expected based on testing, but did not significantly propagate beyond the area of fire exposure caused by the burning of the decorative band at the top of the wall, the decorative band at the top of the 32nd floor and the medallions. As the fire progressed along these materials, it continued to involve the EIFS, but the EIFS was not the primary cause of the continued progression of the fire.
The primary lesson learned was:
Exterior wall systems are frequently pre-manufactured off-site and shipped to the job site. Since construction sites typically do not contain sufficient space to stage curtain walls, they are frequently installed near the time of delivery. It is virtually impossible to confirm compliance of such systems when already installed on the building. In addition, the foam plastic is encapsulated and cannot be verified to comply with applicable code requirements. As such, the third party inspections required during fabrication is a fundamental part of the assurance process.
Other lessons learned include:
Exterior insulation and finish systems are just that - they are systems. The installation must include all constituent components in accordance with the tested assemblies to provide a system that meets applicable code requirements and provides the level of protection intended.
Other similar looking, yet untested materials/assemblies may constitute an unacceptable hazard.
Jesse J. Beitel is with Hughes Associates, Inc. Douglas H. Evans is with Clark County, Nevada.
- International Conference of Building Officials, Uniform Building Code, Whittier, CA, 1991.