Custom Wood Window Sills and Sill Trim

Standard widths for repeatable openings. Custom profiles for project-specific window details.
Lyngou supplies wood window sills for prefab buildings, residential developments and commercial projects. Choose one of five standard widths for interior or confirmed exterior applications, or send a window detail for a custom sill profile and coordinated trim package.
For exterior use, treatment, coating, drainage details and the wall interface are confirmed around the approved project specification.

Standard Profiles

Custom Sill Details

Export Project Supply

Standard Wood Window Sill Sizes

Five standard profiles for repeatable window openings.

The wood window sill sizes can be specified for interior or confirmed exterior applications. Length, projection, material, treatment, finish and drainage details are confirmed against the approved window schedule.

Finished ThicknessStandard Width
18.5 mm92 mm
18.5 mm116 mm
18.5 mm140 mm
18.5 mm180 mm
18.5 mm187 mm

Sill Fit, Projection and End Details

Width is only the starting point. Projection and end details determine how the sill fits the opening.

Before production, we confirm:

  • Projection beyond the wall or casing
  • Return or horn detail at each end
  • Edge profile and visible thickness
  • Relationship with the casing, apron and adjacent trim

This helps the sill look intentional within the complete window opening, rather than like an isolated board added after installation.

Interior and Exterior Sill Specifications

Interior Wood Window Sills

Selection is based on usable depth, visible edge detail, reveal depth, casing and adjacent interior finish.
In North American schedules, this finished horizontal component is often called a window stool. In the UK, Australia and New Zealand, it may be specified as a window board. The term window cill may refer to either an interior or exterior sill. Your project schedule should state which component is required. 

Exterior Wood Window Sill Water Management Detail

Water management is designed into the wooden window sill profile before treatment and coating are applied.

Exterior Wood Window Sills: Water Management Built Into the Profile

Exterior protection starts with the profile—not treatment alone.

For approved exterior applications, Lyngou can develop an exterior wood window sill with:

  • A drawing-specified drainage slope, such as a 15° bevel, to direct water away from the window
  • An underside drip groove
  • Protected end grain and project-specific end details
  • CA, ACQ or LOSP treatment where required
  • Compatible factory-applied coating, including end-grain protection

Exterior sill suitability depends on the approved timber, wall detail, exposure condition, coating system and destination requirements. Final flashing, waterproofing, fastening and code compliance for the installed window-and-wall assembly must be confirmed by the responsible local project team.

Material, Finish and Custom Sill Specifications

Choose a standard sill width or develop a project-specific section. Approved specifications support consistent repeat supply.

Lyngou supplies custom wood window sills in solid timber or selected finger-jointed construction. Material, appearance, profile and supply format are confirmed together before batch production.

SpecificationAvailable Direction
Width and LengthStandard or drawing-specified
ConstructionSolid timber or selected finger-jointed construction
Primary TimberRadiata pine or confirmed project timber
AppearancePaint-grade or stain-grade
Profile and Edge DetailSquare edge, eased edge or project-specific section
Projection and End DetailConfirmed around the frame, reveal and wall finish; returns, horns or approved end treatment where required
FinishUnfinished, primed, stained, varnished, painted or project-specific
Supply FormatFull lengths or cut-to-schedule components
DocumentationMaterial and inspection records within the confirmed supply scope

Selected finger-jointed pine supports smooth, repeatable paint-grade supply. Solid timber is selected where visible grain remains part of the approved finish.

Confirm

Approve

Produce

Identify & Pack

Once approved, the sill section, material, finish and identification requirements become a repeatable production reference for multiple rooms, buildings or later project phases.

Send your window schedule, sill section or reference sample for a project-specific quotation.

Coordinate the Complete Window Opening

The sill, casing and jamb should work as one opening package.

A coordinated wood window sill trim package may include:

 

  • Wood window sill or window stool
  • Jamb extensions and reveals
  • Head and side casing
  • Aprons, backbands and adjacent trim
  • Cut lists and opening-based labels

For replacement or matching projects, send a cross-section, reference photo, and opening dimensions. We can assess the sill profile, projection, and related trim details before production.

Complete the opening with coordinated wood door and window casingwood trim and molding options and wood baseboard trim.

Interior Window Stool Casing And Jamb

Interior window stool, casing and jamb/reveal coordinated as one opening package.

Project Supply and Export Packing

Prepared around the opening schedule—not shipped as unidentified timber bundles.

Standard and custom wooden window sills can be supplied for individual buildings, repeat prefab programs and multi-unit projects.

Opening Based Labels

Opening-Based Labels

Surface Protection

Surface Protection

Packing Lists

Packing Lists

Export Coordination

Export Coordination

Casing, matching trim and selected building components can be coordinated within one project supply package.

Wood Window Sill FAQ

Can the five standard wood window sill sizes be customized?

Yes. Standard widths provide a starting point, while length, projection, edge detail, material and finish can be developed around the approved window detail.

These terms can describe related components. Window sill is the broad term; an interior sill is often called a window stool in North America, while window board and window cill are common in the UK, Australia and New Zealand.

For an interior wood window sill, the best material depends mainly on the required finish. Selected finger-jointed pine provides a smooth paint-grade surface, while solid timber suits stain-grade or clear-finished work. For exterior sills, confirm the timber, treatment, coating and drainage detail against the project conditions.

Yes. The five standard profiles are suitable for confirmed exterior applications. Timber, treatment, coating, drainage detail, end-grain protection and the wall interface must match the project’s exposure conditions and destination requirements.

Yes. Send a dimensioned section, clear photo or physical reference sample. We will assess the profile, projection, material, finish and production scope.

Yes. Where included in the agreed scope, Lyngou can coordinate sill, casing, jamb-related components and matching trim as one opening-based package.

Send Your Window Detail

Send your sill section, window drawing or reference image. Include the required width, length, quantity, material, finish, delivery destination and target schedule for an accurate project quote.

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