Solved: How to Cover Old Window Sills with PVC

All over the country, homeowners are forced to paint old wood window sills and trim year after year.

Even after replacing the window with a new vinyl replacement window, the old window sill is still exposed to the rain, wind and sun.

A common remedy is to hire a contractor to bend aluminum to fit over the window sill.

There are a few problems with this method of window sill cover protection:

  • Matching the window frame color - White aluminum has a different color look than white vinyl window trim;
  • Aluminum still requires maintenance periodically - The paint on the aluminum can chip and peel over time;
  • And finally, if you have a dozen windows to do, the cost of hiring a contractor to perform the labor on all those windows can add up.

So the solution could be a window sill replacement, but which material?

The best solution is to install PVC window sill cover - vinyl extrusions made specifically to cover old wood window sill and surrounding trim. No more reconditioning or having to paint them as you do with wood.

With PVC sill you eliminate any maintenance forever!

I will explain how to do that in a minute.

See also: How to install bubble wrap on windows?

Table of Contents

Let's dive right in.

What Purpose Does a Sill Provide?

The main purpose of the exterior window sill is to protect the bricks, concrete and masonry from the elements. It also drains the moisture condensation and rainwater that runs down the wall away from the window.

On the other hand, interior window sill is serving as a structural window support and to improve aesthetics of an otherwise naked wall. Sills are also perfect place for holding your houseplants.

Window Sill Wrapping Made Easy

Vinyl is a truly maintenance-free product. The vinyl window sill extrusion has been pre-formed to fit any window sill in America. That way, homeowners with a basic knowledge of tools can install this product themselves, saving on costly labor charges.

An instructional video will assist you with the project. Read below to learn about the installation video showing how to install plastic window sill cover.

The instructional video "Window Sill Cover Wrapping Made Easy" shows you how to cover the window sill with a PVC extrusion, so you never have to paint again. Also, the video shows you how to cover the remaining exterior wood trim using vinyl angle trim. The end result is a vinyl window exterior that never needs maintenance again!

The Window Sill Wrapping Process

How can you cover up a horrible windowsill?

You can paint the sill wrap and angle trim to match the exterior of your home. Krylon makes spray paint for plastic patio furniture that works well. However, keep in mind that paint can peel, chip, and fade over time. Raw vinyl is maintenance-free, but applying paint creates a potential maintenance issue in the future.

The two pictures below show the sill wrap piece being applied. The picture on the left shows how it fits on the wooden window sill. The picture on the right shows the piece installed before the end caps are installed. Even the wood trim below the window sill gets covered using a 2" x 2" L-Angle trim.

The pictures below left show the end cap before being cut and installed. The cap is 6 inches long and can do both ends of a sill nose. Notice the legs on the back. The sealant is applied to the legs to hold the cap in place. The picture below right shows the cap installed.

You can cut the sill wrap with a chop saw using a fine-tooth carbide blade, or you can use a hacksaw if necessary. You can use a hacksaw or jigsaw to accomplish notching.

Here is the end result. Notice that the wood trim below the sill has been covered as well as the wood around the window.

Repairing Wood Window Sills

Why do window sills rot?

If not maintained regularly, natural materials like wood deteriorate due to exposure to the wind, sun and rain. Damaged paint is the fist sign before the old sill rotting takes place. 

Homes that were built prior to 1960's usually have wood sash windows. These windows have exterior sloped wood sills to drain water away from the window.

That also answers the most common question why is a window sill angled.

There is also wood trim on the sides and across the top of each window. The window's energy efficiency increases tremendously if you replace the wood sashes with a PVC pocket window.

During the cold winter months, it can drastically reduce heating costs.

But, wait - what about the wood that surrounds your windows on the outside? You have that brick molding around the edge of the opening and the wood sill on the bottom.

You still have to periodically maintain that or even replace it in case of deterioration. If a wooden sill is not maintained regularly, after a few years you will have a rotted windowsill.

How do you fix peeling paint on a window sill?

First you need to fix the exterior trim.

After you scrape out and fill any rotted window sill areas with an epoxy mix, try to sand the surface thoroughly.

What other prep do you need to do before attaching your pvc trim, caulking repainting?

You could solve this by wrapping the wood with aluminum as it is more durable than wood.

But, aluminium sills also have to be painted, so you are still dealing with a paint issue.
In addition, to install the aluminum, a homeowner will need to have a special bending tool. You will have to hire a professional as you do not have the tools or knowledge to use them properly.

However, there is a PVC product that homeowners can install using only basic tools, like utility knife, pry bar and caulk. The end result is a maintenance-free window sill, and it looks better than the aluminum process.

Exterior Window Sill Replacement

By covering your wood with PVC window sill replacement, you eliminate the need to paint or replace your wood ever again. Your window sill will look like new even if you have some wood rot - repair the damaged wood with filler, then install the vinyl cover.

How to install a pvc window sill?

For those eager to get started, here is a pdf manual on how to install replacement window sills.

Now let's explain each step.

First, remove any paint that is peeling of before attaching the trim. Cut the sill wrap extrusion with a circular saw or chopsaw, and cut it 1 1/2" longer than the sill itself as you have to attach the caps on the ends.

The sill piece has to be notched to fit around the brick molding on each end. To accomplish that, use a jigsaw or hacksaw.
It is important to use an extreme weather adhesive, like Dynaflex 230. If you use a bond that can't withstand sub-freezing weather, the vinyl can come loose from the wood.

The trim covering the brick molding and surrounding wood is an L-Shaped piece. To fit most applications, the trim comes in several sizes.
You can rip it down using a table saw, jigsaw, or simple plastic cutting tool.

So, no matter what size of wood you have around your windows, the L-Angle trim will fit.

You can learn more about this wrapping process on youtube:

How Much Does it Cost to Replace a Window Sill?

Depending on the new sill length (measured from jamb to jamb), the material will cost anywhere from 10 to 50 bucks for the 96" sill.

But that is not all, unless you install the new sill yourself.

A professional window replacement installer or carpenter will charge around $200 to replace the old sill. Additional repair of the wall or window will only add to this cost.

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