Improperly Installed Windows a Common Problem

I was driving back from my last inspection today and noticed a house under construction down the street.  The brick was starting to go up but the windows and moisture barriers were installed.  I could see from the street that the windows were not installed properly.

 

window install

Note the lap of the house wrap
at the bottom flange of the window.

Improperly installed windows are a common problem in the Houston area.  I look at many homes under construction where the exterior moisture barrier is not properly flashed at the windows.  Normally you cannot see this unless the house is in ore near the 'top out' stage of construction prior to installation of the siding.  As you can see in the photos one of the most commonly made mistake is improper flashing along the sill of the windows.  The windows shown have a sill flashing but the flashing and windows were evidently installed prior to the house wrap and no provision was made to lap the sill flashing tape over the windows after the wrap installation.  This will result in water running in and rotting the sheathing below the windows and then running into the walls of the building.

 

improper sill flashing

flashing tape applied behind
house wrap at the bottom of the windows.

Unfortunately it is impractical to pull the flashing tape loose since it will very likely be damaged.Correction of this problem will be costly to the builder because it will require that the windows be removed so a new sill flashing can be installed and lapped over the house wrap.  Had the builder followed the ASTM 2112-07, which is the standard for window installation most have adopted, this would not have been a problem.

 

Comments

Thu, 06/18/2009 - 15:04 — erobinson

Today I was working near a

Today I was working near a building being constructed with stucco siding at framing stage and noticed that they were not lapping their sill flashings over the felt moisture barrier applied in preparation for the stucco lath and scratch coat.  On the building I observed it appears unlikly this will create a serious problem because the house wrap used to dry in the building during construction was in good condition; however, in many cases I find severe damage to the house wrap often below the windows which would clearly leak.  If you do not lap the sill flashing over the felt installed just prior to the stucco, as shown to be improper in the provided photograph, then the felt serves no purpose at this location and could affect windows or wall penetrations below.

 

window sill flashing in stucco

This is a common detail for builders.  The house wrap is installed to dry in the structure during construction and is left to be damaged through punctures and tears.  The windows are installed and flashed permenently to this house wrap with no provision to lap the sills over the felt to be installed later.  Penetrations in Houston are seldom flashed or addressed.