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Building Management Hawaii December/January 2014 - (Page 22)

Cementious Coating Vs. Polyurethane Foam How best to repair below-grade waterproofing By Sean Dunham Waterproofing B elow-grade waterproofing is the system that keeps or fails to stop basements, elevator pits and below ground parking from flooding. Without below-grade waterproofing these spaces would be uninhabitable and accelerate the damage to structural concrete and reinforcing. Below-grade waterproofing has to stop a combination of hydrostatic pressure and capillary action. Hydrostatic pressure usually comes from two sources-ground water during heavy rain periods and tidal action in areas below sea level (a common issue in Waikiki). Capillary action is cement's propensity for absorbing water like a sponge. Below-grade waterproofing falls into two categories-negative side and positive side. If you imagine you are in a tunnel below ground, the wall you can touch is the negative side. The wall outside buried in the dirt is the positive side. As you can imagine, fixing or reapplying positive side waterproofing in old buildings is incredibly expensive as you would be required to trench out the dirt to expose the surface. There are also areas that are next to impossible to gain access, including the horizontal slab, walls abutting up to neighboring buildings and pits. The costs to gain access to the outside of the leak is often much more expensive than the actual cost of the waterproofing. That's when it's time to use systems that can be applied from the interior (the negative side). ultra-dense surface that does not allow water in its liquid state to pass through but water vapor can still pass through. Since the water vapor can still pass, it doesn't condensate between the cementious coating and the substrate. This condensation is what causes delamination and blisters in conventional coatings when applied as negative side waterproofing. The downside to cementious coatings is Repair Approximate cost Effectiveness Cementious Coating $12 a Square Foot 2 Polyurethane Crack Repair $125 a Lineal Foot 3 Polyurethane Curtain Wall $30-40 a Square Foot 1 The two most common and successful products are cementious coating and polyurethane foam grouts. Cementious Coatings Cementious coatings come in a few different formulations, but the concept behind them is to create an their inability to handle movement. So if your building is experiencing settlement issues, it is not the right fix. Also for horizontal applications, if people or vehicles transverse the area, you need to add a concrete topping over the cementious coating since it doesn't have good wearing properties. Polyurethane Foam The other common fix for belowgrade areas is expanding polyurethane foam grout. It can be used in one of two 22 December 2013 - January 2014 BMH www.buildingmanagementhawaii.com http://www.buildingmanagementhawaii.com

Table of Contents for the Digital Edition of Building Management Hawaii December/January 2014

Signs & Safety How Do I Get Out Of Here?
Signs Of A Safe Building
A Sign From The Feds
Water Savings Coming Clean With Recycled Water
Water & Energy: Two-For-One Savings
Solar  Hawaii’s Leaders In Solar
Waterproofing Cementious Coating Vs. Polyurethane Foam
Sky Arches
The $1 Million Mistake
Seal The Deal
Resin Injections Save Basement
Waste Management Keeping The Trash Industry Clean
Special Offer
Assistance Animals Making Room For Rover
Green Cleaning Be Green: Resources & Tips

Building Management Hawaii December/January 2014