In this article, I want to talk about some great ways to waterproof an exterior door when it is installed on a concrete slab on grade with a stucco exterior home.  This kind of installation is typical for the Southwest desert region.

There are two primary areas to pay close attention to when installing the door: threshold and flashing.

1. The Flashing

The first step in the process is making sure the opening you are going to install your door in is properly “flashed” to prevent water infiltration.  All too often, there is no overhang to protect the opening from water running straight down the face of the wall.  Because stucco has a porous surface that wicks water below the surface, all the caulking and sealing you could do to prevent water from getting in just isn’t enough.  The water is already under the surface and moving down.   There must be a barrier that forces water away from the opening.  This can be achieved with soft flashing or metal flashing under the stucco finish.

At Younger Brothers Doors & Trim, we have designed a simple compound angle flashing, referred to here as “Metal J Strip,” that can be installed before the lath goes on.  It must be installed precisely to align with the door frame.  This method allows for the door and frame to be installed after the lath and stucco have been installed, which prevents a lot of damage to the frame during these operations.

By using this method, you will achieve three important objectives:

  1. You have provided a place for any moisture on the face of the stucco to drip off at the radius of the return
  2. You have created a dam at the metal flashing that stops the moisture from infiltrating the opening
  3. You have a clean metal surface on which to caulk and seal the door frame

This method also provides an aesthetically pleasing Southwest finish to the opening.

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2. The Threshold

For sealing at the threshold, you will need to make sure you are starting with the right products in order to achieve a watertight barrier.

The threshold is a major component of the weatherproofing process.  We use an integrated threshold that gives us a built-in dam and synthetic components to prevent any rot or mildew.  The one we use also has a “tile” lip on the back edge.  This allows for floor tile to slip under the raised edge and alleviates the need for grout up against the face of the threshold.  This is most likely the first place grout will crack.

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Installing the Door Jamb and Threshold

Now let’s look at one way to install the door jamb and threshold.

First, make sure the floor is clean so that the sealants will adhere.  Because the concrete may effloresce, allowing a slight powdering of the surface, it is hard to count on this sealant lasting as a water barrier, but it will help fill some of the voids and create a smoother platform to start from.

Next, we want to apply two beads of a good water block sealant to the floor and up the sides a couple of inches.

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Now it is time to put a plastic pan on top of the two beads of sealant.  There are a number of pans on the market; we prefer to use one that is adjustable in length.  The pan will have end caps that should be tight to the framing.  It will be pressed into the sealant that you ran up the opening.

Just as a side note, it is sometimes hard to get the pan just right in width.  It is best, as in the photo, if the pan can lip over the edge of the slab.  You may have to cut the outer turn down in order to use the pan.  This is not the best installation, but we can make this work as you will see in the next few photos.

Once you have the pan in place, cut a couple of strips of adhesive backed flashing paper and run them up the opening about 6 to 8 inches.  This ensures that any moisture that gets past our other precautions will be directed into the pan and out over the edge of the concrete floor.  Remember, water will always continue its quest to travel down.

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Next, we install an aluminum angle sill to protect the exposed portion of the pan.  This is also the point at which you can cover the cut edge if you had to cut the pan in order get it to fit on the width.  If you have cut the front edge off, you will want to run a heavy bead of sealant at the leading edge of the angle sill itself.  If you were fortunate enough not to have to cut the edge off, it is better not to put sealant under the angle sill.

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Before you set the door jamb and threshold on the pan and angle sill, run one more bead of sealant on top of the angle sill.  Once again, we want to prevent water from coming in and at the same time allow it to escape on its downward journey.   Be sure that you keep the sealant back far enough that it will not ooze out in front of the threshold.

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You are now ready, if you used our metal flashing idea, to place a bead of sealant on the metal flashing and set your door jamb into the opening.

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When you have shimed and secured your unit, centered in the opening, you will want to run a single bead of matching Silicone caulking along where the edge of the threshold meets the top of the angle sill.

If all went well, you have a door opening that will stay dry under nearly any storm condition.

For more professional advice or to see our wide selection of doors, windows and trim, contact Younger Brothers today.