Window Keystones

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Stucco Keystones

  • Free Shipping direct to your jobsite or home
  • Will not Rot, Warp or Infest like inferior wood products
  • Add sophistication to window trim with imitation pre-cast window keystones
  • Can be installed during construction, or after as a renovation due to light weight
  • Painted any color of your choosing after installation

Window Keystones add a unique flare and style to window headers and door headers. Our lightweight keystones can be installed either during new construction or after a renovation, and will not rot, warp, or become infested. The size of a keystone will be determined by the trim you're using it with, keystones should generally be 1-2 inches taller than the trim to provide enough visual impact. The shape or design of the keystone is largely a personal preference, and should generally fit with the style and theme of the home.

Choose the Classic Keystone if going for a concrete-style appearance, or one of our more ornate polyurethane keystones like the Lion Head Keystone or Scroll Keystone for a more refined look.

What is a Keystone?

Keystones have been used in construction projects for thousands of years, and while they're no longer required structurally, they provide a classic, timeless look to any project. They can be used on any building material including brick, stone, stucco, EIFS and even vinyl.

Keystone Designs

When selecting the placement of keystones, you want to first start with the most often seen doors and windows, and fill in the rest as budget and time permits. A few key places include the front door, garage doors, and large windows on the front of the home. Smaller or less ornate keystones can be used on dormers and less prominent or visible windows.

Keystones are designed to be embedded into stucco trim!

You want to choose your keystone size based on the size of your stucco trim - the winged portions should protrude just slightly above the trim itself. Most keystones are designed with a larger depth, to accommodate trims of various sizes. If you received a keystone on site that doesn't match the depth of the trim, it can be padded outward by simply using a piece of flatband or styrofoam trim.

  • Take $100 Off Orders Over $1000 with Coupon BULK10
stucco window trim


Although purely decorative, keystones are a a great way to accent your windows and doors. Keystones should be initially placed when installing the rest of the molding and window trim, however - a center can be carefully cut from existing moldings to provide a place for keystones.
Check out our guide for selecting the appropriate keystone size for your window trim.

Where to Buy Keystones Online

Whether you're in California, Texas, New York, Florida, Ohio, Nevada or Connecticut - we ship right to your job site. If you're a builder, project manager, architect, designer or contractor looking for premium imitation-concrete products to compliment your stucco, brick or masonry project, send us an email and we'll be happy to help!

 We can provide contractor discounts up to 50% off on orders over $3000.

Decoramould is an exterior window keystones supplier for exterior home renovation, retrofits and alterations throughout the U.S.A. and Canada. Customers can buy window  keystones online, and have their exterior keystones purchase shipped directly to them.

Our foam keystones look like high end concrete keystones, but weigh only a fraction as much - and often cost only a fraction as much as well. They can be installed during the initial construction of a home or building, or added on as decorative keystones after construction. Installation is as easy as adhering them to the wall surface, for more information see installation instructions.

Sizing the Right Keystone for Your Window Trim

Keystones undoubtedly add some character to your window trim, but some care does need to be taken when selecting which one to have installed. A keystone that is too small won’t fit properly into the trim, leaving a portion of it exposed. A keystone that is too large (as seen below) on the other hand, can be disproportionately large and also look out of place.

A keystone that is obviously too large for the trim that "contains" it.

The key question (get it?) then is, how do you select the right size? As a rule of thumb, keystones should be 2-3″ larger than the trim they’re being fit into. This becomes difficult with smaller window trims that are only 4″ in size like Trim 001, and in such cases I have seen contractors actually cut the bottom 3″ off a keystone so that it is height proportionate. Don’t forget to re-apply the cementitious coating after doing this.