The best cast stone window sill mold depends on the sill’s dimensions and the number of pieces you need to make. The Stone Master Molds water-table mold is designed specifically for two window sills per mold, while the Master Molds 18-inch mold makes three shorter water tables. For longer custom edges, Master Molds’ chiseled edge liners offer reusable form options. The GlobMarble mold is a larger-format choice for a sill or stair-style piece.
| Product | Best suited for | Key dimensions or output |
|---|---|---|
| Stone Master Molds Water Table Mold | Two window sills per cast | 20.25 × 4.5 × 2 inches each |
| Master Molds 18-Inch Water Table Mold | Shorter sills, trim, and borders | Three 18-inch pieces |
| GlobMarble Stair/Window Sill Mold | Larger single pieces | Approx. 32 × 11.75 × 1.5 inches per section |
| Master Molds 12-Foot Chiseled Edge Liner | Long edge-forming runs | 12 feet long; creates a 2-inch edge |
| Master Molds 8-Foot Chiseled Edge Liner | Shorter edge-forming runs | 8 feet long; creates a 2-inch edge |
Stone Master Molds Water Table Mold
This mold is designed to create two cast stone water tables or window sills, each measuring 20.25 inches long, 4.5 inches wide, and 2 inches thick. The pieces are angled forward to help direct water away from a building.
Best for: Buyers who want a mold specifically intended for window sills and need two matching pieces per casting. The listed feature that no release agent is necessary may also simplify demolding and cleanup.
Consideration: Each finished piece is 20.25 inches long, so this mold may not suit openings that require a single longer sill.
Master Molds 18-Inch Water Table Mold
This mold produces three cast stone water tables, each 18 inches long. The pieces can be used as window sills, trim, or borders between materials such as stucco and stone. Their tapered shape and underside drip slot are intended to encourage water to move away from the building.
Best for: Small projects that need several shorter, matching pieces or decorative transitions between exterior materials. It is a practical alternative to the 20.25-inch mold when 18-inch pieces better match the project plan.
Consideration: The 18-inch length is fixed by the mold; check the required opening dimensions before choosing it.
GlobMarble Stair and Window Sill Mold
The listed mold measures approximately 33.5 by 12.5 by 2 inches overall. Its product details list a section size of about 32 by 11.75 by 1.5 inches. It is made from two-component polyurethane or silicone rubber, and the listing recommends a concrete release product to help protect and prolong the mold’s life.
Best for: Buyers seeking a wider, larger-format mold for a sill or stair-style cast piece. Its listed dimensions make it a different option from the narrower water-table molds.
Consideration: The product information specifies approximate measurements and recommends using a release agent. Confirm the intended finished dimensions and release requirements before casting.
Master Molds 12-Foot Chiseled Edge Liner
This 12-foot liner creates a concrete edge that is 2 inches wide and 2 inches deep. It is self-supporting and designed to fasten directly to a substrate. The listed features say silicone and release agent are not necessary, and that the production-quality mold can be used hundreds of times.
Best for: Projects that need a long chiseled concrete edge or repeated edge-forming runs. Its longer length may help reduce the need to join shorter liner sections along a continuous project.
Consideration: This is an edge form liner, not a dedicated, complete window-sill mold. Choose it when its 2-inch edge profile fits the design.
Master Molds 8-Foot Chiseled Edge Liner
This 8-foot liner has a 2-inch width and depth and is designed to fasten directly to a substrate. Like the longer version, it is self-supporting and does not require silicone or a release agent according to the listed features. The mold is described as reusable for hundreds of uses.
Best for: Shorter projects or buyers who need the same 2-inch chiseled edge profile in a more compact liner length.
Consideration: Its 8-foot length is shorter than the 12-foot option. It also forms an edge rather than a complete window sill, so compare its role with the dedicated water-table molds.
Buying Guide: How to Choose a Cast Stone Window Sill Mold
Which mold dimensions should you check?
Measure the required finished length, width, and thickness before selecting a mold. Compare those measurements with the listed dimensions for each product. The two water-table molds produce pieces 18 or 20.25 inches long, while the GlobMarble listing gives larger approximate dimensions. Allow for the actual project layout rather than assuming a mold will fit an opening without modification.
Do you need a complete sill or an edge liner?
Choose a dedicated water-table mold when you want a shaped sill or trim piece with a water-shedding profile. Choose a chiseled edge liner when the project calls for a particular concrete edge treatment. The liners listed here create a 2-inch edge, but their product details do not describe them as complete window-sill molds.
How many pieces do you need?
Compare output per mold: the Stone Master Molds design makes two pieces, and the 18-inch Master Molds design makes three. Consider the number of castings required for the whole project, not just the number of pieces produced in one casting.
What should you know about release agents?
Several Master Molds products state that a release agent is not necessary. The GlobMarble listing recommends a concrete release product to protect and prolong the mold’s life. Follow the product instructions and account for release requirements when planning materials and cleanup.
Frequently Asked Questions
What is a water table on a window sill?
A water table is a shaped exterior feature intended to direct water away from a building. The listed window-sill molds describe angled or tapered pieces, and one includes a drip slot underneath.
Which listed mold makes the most pieces at once?
The Master Molds 18-inch water-table mold is listed as producing three pieces per mold. The Stone Master Molds mold produces two.
Are the chiseled edge liners complete window-sill molds?
Their listed purpose is to form a 2-inch chiseled concrete edge. They are not described as complete window-sill molds.
Does every mold require a release agent?
No. The Master Molds listings state that no release agent is necessary. The GlobMarble listing recommends a release product. Check the instructions for the specific mold.