Water Leaking Window Problems, and The Solution


Bad flashing technique usually is the culprit for water leaks above windows and doors.  Here is how to spot it and fix it right.


By William Decker, CRI, CMI                                                                            


    As a Certified Master Inspector, most of my business is performing pre-purchase inspections for people who are buying houses or condominiums.  But pre-purchase inspections are not our only job.  People will call us to evaluate work they had done on their house, sometimes leading to lawsuit litigation.  We also do maintenance inspections, when a homeowner wants to have someone experiences look at their house and point out things that should be repaired, replaced or changed.  We also do safety inspections and phased construction inspections.


    I have found a special niche of inspections in my area (Greater Chicagoland Area) with the introduction of buildings constructed of a masonry product called splitTypical Split Faced Block Building faced block.  These buildings require special water management construction techniques to compensate for the single wythe (one 8" block thick) walls and the porous nature of this material.  Water enters the block, mainly, through the top of the parapet walls of the roof area because the masons did not cover the parapet walls with a reliable flashing membrane.  They usually just lay a layer of 2" thick Renaissance stone (just polished concrete) which allows water to drain through and accumulate in the block cells.  Some of this water drains out (leaving the white stains, called efflorescence) but some of it drains in, wetting the insulation, buckling hardwood floors and supplying moisture to allow mold growth.  The older brick walls had multiple layers of brick with air spaces between them.  They were covered with clay coping tiles whose sides were open, allowing these air spaces to ventilate.


    That describes the main problem, in a nutshell.  The main source of this water is through the top of the parapet walls.  as proof, I would note that split faced block buildings with pitched, rather than flat, roofs have not suffered from these problems.  Many contractors seem to provide a "silver bullet" solution, seal the outside of the walls, either with a heavy

rubberized "plugger paint, or with a penetrating sealer.  This is a bad idea, especially the plugger paints, which actually trap moisture in the walls and prevent drying to the outside.  The penetrating sealers are a good idea, but they are a expensive (applied according to manufacturer's specifications) and re-application has to be done every 5 years or so.  Many condominium associations in this area have found out the hard way that the suppose 20 year warranties are no good if the company goes out of business.  There are also "contractors" who claim they do water sealing, but just wind up with a garden sprayer full of wood sealer that they bought at the local Home Depot.  If done, it is best to have it done by professionals.


Masonry window flashing detail

  But sealers are an attempt to fix the problem after the fact.  There are two unbreakable rules when dealing with water management in buildings.  1) DO NOT let water of any type enter the wall assembly.  2) Because #1 is not 100 possible, give water that does enter the wall a way to drain OUT.  That is, construct the building in such a way that any water that does enter has an easy way to get out, otherwise it will drain in.


  The most common symptom of water intrusion that I have been seeing these last years is water leakage above windows and doors.    Because windows and doors are openings in exterior, structural walls, they must have 0he area above them supported. This is done with steel lintels, installed over the penetration so as to support the brick or block or stone above.  But, because there will be water in the wall (rule #2), there must be drainage flashing above these lintels.  This flashing is usually a special rubberized membrane.  It is laid in downward stepping fashion, through the wall and over the exterior side of the lintel.  This flashing forces downward traveling water to drain out above the window lintel.  Some builders will also install weep wicks, lengths of a rope like material that extend up the membrane and help to wick the water out by evaporation.Lintal drainage space grouted shut


  The main portion of the flashing that must go all the way through the walls (not always done right) and have its rear end turned up and secured to the inside of the wall (called back flashing and also not always done).  There should also be separate flashings at the two corner edges above the window or door (called end flashing).  These serve to force the water to drain out and not run down the sides.  Another important feature of this flashing should be a drip edge.  This is a piece of metal, inserted into the lintel space, under the membrane, that will work to take the water away from the lintel edge and drip off.  Drip edges are usually made of stainless steel so as to last.  Without a drip edge, the water surface tension will cause it to just run around the outside edge of the lintel and cause it to rust.


  But these details are rarely done.  Many times, the masons will put mortar in the space between the brick/block and the lintel (right).  I regularly get calls from people who recently had their house or building re-pointed (tuck pointed) and now have water coming in above their windows.  The masons saw a space and filled it with mortar.  This causes the water to backup and finally drain inside.  Some people, in an effort to avoid the regular re-painting maintenance of wooden window frames, decide to have them covered with metal cladding.  But the people who do this work don't always understand the reason for the open space above the lintel.  They will extend the cladding over the drainage opening and caulk it shut. (far left).  This often causes the water in the wall to rust the lintel, which expands and causes cracking at the upper window corners (above).  And the most common cause is a homeowner getting carried away with home maintenance and caulking these spaces shut themselves.  I have dubbed this problem as "Front Damming".  The water draining down the wall assembly cannot drain out and goes the only path left open, in and over the doors and windows.


    The solution to this is usually easy.  Remove the front damming.  Chip out the mortar or scrape out the caulk.  A good addition would be to have a professional form some stainless steel drip edges and insert them, under the flashing membrane, into the lintel space.  This gives the waster a clear and easy path out of the wall.


    I hope that this article helps to better inform homeowners, and many tradesmen who have never had any professional training (about 82%) on how to build it right the first time or how to fix it right, and one time only.