Sealed Laps on Horizontal Siding

Do you have sealed lap siding? If your home was built prior to 1960 and you have cedar lap siding chances are you do? What does it mean?

Lap siding is meant to overlap each piece in order to allow air and moisture flow to occur.  There should be a small gap that should be between each piece of horizontal lap siding.

Over time the many layers of paint and sometimes caulking will fill this space.  Because air and moisture needs to flow from these cracks it typically is the first sight of failure after a new paint job.  The reasoning behind this is simple.  If the laps are sealed the air and moisture has nowhere to go and will eventually push air and moisture out of these cracks.  This will create bubbles in your new exterior paint job.   In Portland we see this around 80% of the time when estimating lead lap siding homes.   It once was thought that a home needed to be completely sealed in order to keep the moisture out of the house.  So house painters and DIY’ers would caulk each wood lap making sure no air or moisture could enter.  The problem is that the air and water cannot escape either.

In order to properly prepare these types of homes it requires us to open the lap siding crack.  you can watch the video below that goes over a very simple way to open these laps on your exterior painting project in Portland.  If this is not done prior to repainting of your home you will very likely experience bubbling and/or peeling at these laps.


Latex paint acts a lot like a large stretchable shell around your home. with numerous layers of existing paint underneath your most recent paint you get a pulling effect.  With today’s new and high quality paints they are able to form very strong and tight bonds around the exterior of your home.  These new thick and high quality paints will actually pull on your existing layers of paint causing failures much sooner than if we used a light breathable coating like a solid body water-based stain. The reason why we use Sherwin Williams Woodscapes or ArborCoat from Benjamin Moore on these types of projects  is so that we can reduce the build up of paint layers.

On these lead paint homes more is not always better.  Some house painters might say they are going to throw a full coat of primer on your house just to be sure everything is primed.  The problem with this is that its just adding another layer of coating that the bottom layer of paint needs to hold on to.  Think heavy pulling effect after numerous rounds of this type of paint application.

Do you have sealed laps on your siding? Are you getting your home ready for the Portland Real Estate Market?

Request a quote today