Saturday, August 4th, 2012
Written by: hhollingsworth
Multi-family, located in the mountains
Water leaking into parking garage; fireproofing was scraped off during initial repair
Replace, repair, recoat.
Proper detailing of waterproofing during the design phase; asking questions during construction regarding the waterproofing methods.
When homeowners noticed water leaking into the underground parking garage, they contacted SBSA to inspect their multi-family mountain condominium property. The garage itself lies below a series of three buildings with exterior plaza areas between each building. Directly below portions of the outdoor plaza areas above that were exposed to the weather, there was severe corrosion of the corrugated metal decking.
In reviewing the original design documents, SBSA noted several issues:
- The floor system at the plaza consisted of a concrete and structural steel composite slab system with a concrete topping slab placed over it as a wear surface
- No waterproofing was called out between the slabs in the design documents
- No type of exterior topical waterproofing applied to the top surface of the plaza slab.
SBSA suspected that water entered the interstitial areas of the composite system through control joints and cracks in the topping slab; once there, it became trapped within the flutes of the metal decking where it corroded the metal, which is what was causing the significant leakage throughout the garage.
Water leaking into the slab system resulted in additional damage because it soaked the spray-applied fire protection on the structural steel members below the plaza and first floor areas of the buildings above. Because water was held against the steel by the fireproofing, it caused additional and significant corrosion. The building owner attempted a repair by scraping the fireproofing away at numerous locations, then simply painted over the steel. However, at the time of SBSA’s inspection, the fireproofing had not been replaced. The missing fireproofing leaves the structure vulnerable to fire and is a clear violation of the building and fire codes.
To date, no intrusive testing has been performed on this property to verify that no waterproofing exists between slabs. Regardless of its presence or not, because of the resultant damage, repairs to this system would require the complete removal of the entire plaza composite deck system at areas exposed to the elements above. The structure would need new metal decking and structural concrete slabs in areas of significant damage would need to be fully replaced. After that, a fluid-applied waterproofing system, including a drainage mat for proper flow and elimination of infiltrating water, needs to be installed.
A new topping slab would then be added with two-stage promenade drains to handle surface as well as sub-surface water. Lastly, all water-soaked fireproofing at steel support beams and columns would need to be removed and the underlying steel cleaned, repainted and recoated with new fireproofing material.
This unfortunate and costly leakage situation was preventable. Proper attention to waterproofing and drainage during the design process for any exterior deck surface is a must. Designers must account for all possible paths of water infiltration and allow for adequate drainage in order to prevent damage to structure and finishes. Not doing so leads to very expensive consequences.