Seattle Home Inspector's Blog

head_left_image

How to flash siding butt joints

A common problem with cement board siding products (and some other types of horizontal lap siding) is that older installation guidelines called for caulking the joint instead of flashing the joint.

This has proven problematic over time as caulking the joint results in unsightly surface appearances due to the different textures as well as resulted in failure of the caulk joint and associated ongoing maintenance.

Since newer installation guidelines do not recommend caulking this joint but instead recommend leaving a small gap and flashing behind the ends of the siding, I think it is more prudent to add flashings when it is possible to do so.

If the corners of the siding boards have been face nailed, it can be a little more difficult (though not impossible for experienced siding installers).

Otherwise adding flashings is typically a piece of cake!

Here is what the detail look like.

In this first picture we see what a typical siding joint looks like on a home that was sided with cement board siding and there is no flashing behind the butt joints. The caulk has failed and water can find its way behind the siding.

Failed caulked joint in siding

The following series of pictures will detail how to make a simple flashing that can be slid up behind the joint. It requires no nails.

Depending on your reveal of your siding the flashing length will be ¼ inch less than the reveal. Dog ears will be cut on both sides approximately ¾ inch from the bottom and then folded to create a “stop” that will locate itself on the top of the underlying row of siding but not be so long that it will run into the nails that hold the siding of the row being flashed.

 

Butt joint flashing

 

Note that the flashing does not go up high enough to hit the underlying nail but is still high enough to behind the next row of overlying siding.

 

Once the joint is flashed, it really will not look much different than before it was flashed but water cannot get behind the siding.

 

Charles Buell, Real Estate Inspections in Seattle

* * * * * * * * * * * * * * * * * * * * * * * * *

Seattle Home Inspector

 

The Human Rights Campaign   QR code for Charles Buell Inspections Inc  ASHI.org

 

WA State, Home Inspector Advisory Licensing Board

Comment balloon 9 commentsCharles Buell • October 25 2015 01:00PM
How to flash siding butt joints
share
A common problem with cement board siding products (and some other types of horizontal lap siding) is that older installation guidelines called for caulking the joint instead of flashing the joint. This has proven problematic over time as caulking… more
There are still a lot of these recalled toilet tanks out there.
share
If you flush the toilet and it sounds like there is some sort of jet engine in the tank, it may be a compressed air, assisted flush, type tank. These flushing mechanisms work REALLY well but some of them, like the Sloan Flushmate III/503, are… more
Sick of mold or sick from mold?
share
While you are not likely to get sick from mold, there is a good chance that if you are a real estate agent, or home inspector, or banker, or appraiser, you may very well be sick of hearing about mold. This post will be the first in a series of five… more
Qualified but quality conclusions.
share
This first picture is of a hot water pipe behind a wall taken with an Infrared thermometer. At lower left in the picture is my finger pointing at the line that shows in the pictures below. Any pipe in a wall with hot or cold water in it can slow up… more
Mold on the roof sheathing---and the home is new!
share
There is some staining/discoloration and/or mold or mold-like fungal growth present on the roof sheathing in the attic. This condition may be consistent with the effects of Night Sky Radiation. Night Sky Radiation is when the roof sheathing… more