SuccessfulThrough Wall Flashing Systems Prepared by: Lennel Specialties Corporation www.lennelspecco.com Edited by: Richard Keleher
The Problem This problem can lead to: Damage to interior finishes Tenant discomfort and complaints Indoor air quality problems due to mold and fungus growth The age old problem that the construction industry has been faced with is moisture infiltration in its liquid form into building exterior walls and interiors due to through wall flashing failures. Damage to the structural elements of the building Efflorescence Loss of clients Litigation Owners are no longer putting up with leaky buildings. 80% of construction litigation is due to moisture infiltration problems.
The Solution Design Detailing Consider carefully Materials Workmanship Coordination
Design Don’t design a building that cannot be effectively or efficiently waterproofed
Detailing Use three dimensional details for corners, panning and other intricate details. Think about where the moisture is going to flow when drawing details. Details should be clear and complete. Make sure your details get the moisture out past the face of the wall. CAD makes detailing so much easier. A library of details can be developed to detail most conditions on most jobs.
Materials Copper Core Composites Copper with asphalt saturated kraft paper Asphalt coated copper Copper fabric flashing Benefits / Problems Will last a long time Hard to work with in the field How long will the lap sealant last? Not compatible with sealants
Materials PVC Excellent material to work with, but….. Plasticizer migration will cause it to become brittle and crack over time Not UV resistant Not resistant to some solvents Not very durable AIA/ Masterspec dropped it from their specifications in 1999
Materials EPDM + / - 60 mil membrane hard to bend, fold & lap Adhesive application causes some problems Note: EPDM is now available in 40 mil thickness and can be sealed, lapped and embedded in mastics and mastic type products. Self Adhering Flashing Self sealing at splices, punctures and penetrations Cannot withstand prolonged exposure to UV rays Not compatible with sealants Keep material back 1/2” from the face of the wall Do not bridge gaps greater than 1/4” wide
Materials 16 oz. Lead Coated Copper Will last a long time Excellent for forming end dams and corners Not adaptive to job site conditions Very expensive to purchase and install ( + / - $ 10.00 / sf = + / - $ 2.00 / sf of brick veneer ) Can leach a white residue Lap and joint treatment must be considered Stainless Steel Will last a long time Hard to solder for end dams and corners Not adaptive to job site conditions Very expensive to purchase and install ( + / - $ 15.00 / sf = + / - $ 2.50 / sf of brick veneer ) Can reflect sunlight depending on finish
Workmanship To help avoid these problems: Use clear, concise and complete details Choose user friendly materials Have a pre-construction envelope meeting with: 90 % of flashing problems are due to poor workmanship The general contractor The cladding (masonry) contractor The metal stud contractor The window contractor The sealant contractor The air barrier & flashing installers
Typical: Use Mortar Net! Typical: Provide Insulation (Angle should be on Brackets) Typical: Use Backer Rod to Allow for Deflection
Typical: no insulation! Now this works!!!!!
Typical: Use Metal Flashing with End Dams Typical: Air + Vapor Barrier (dotted)