How to Panel a Bay Window Wall: Angles, Mitres & Symmetry

Surveying each bay facet

Centre facet and two returns — measure width of each flat section wall to wall at skirting top, mid, and sill level. Angled corners are not included in facet width.

Height from skirting to sill bottom often defines dado panelling zone under bay; above sill to ceiling separate zone or wallpaper.

Sill depth and projection — deep Victorian sills may interrupt grid; panel below sill only common.

Corner stiles at bay angles

Typically 135° or 150° external corners between facets — not 90°. Mitre saw set to half of included angle or scribe stiles with compass.

Single stile turning corner rare in thin MDF — two stiles meeting at angle each scribed to adjacent facet plane.

Dry assemble cardboard templates at bay corners before MDF cut.

Calculator per facet with aligned columns

Run shakerpanel.com separately for each facet width with same strip width and target column count where widths allow. Wide centre facet four columns, narrow returns two columns — visual weight centred on street window.

Stile positions at bay corners must align vertically across sill line — mark on floor tape projection lines into room.

Total column count aesthetic not identical each facet — symmetry from street view through glass matters less than interior harmony.

Radiators under bay

UK bays often hide radiator in centre facet — frame or box per radiator guide. Returns may panel uninterrupted.

Depth of radiator plus TRV clears stile — measure before corner stiles fixed.

MR MDF if condensation on single-glazed bays — upgrade glazing separate project.

Curtain pole and blind conflicts

Ceiling-fixed curtain tracks in bay need panelling stop or notch — plan track before top rail height. Final blind depth must clear panelling projection of 9–12 mm.

Roman blinds inside recess — panelling below sill leaves recess clear.

Do not fix strips where bracket loads need solid wall not MDF lattice.

External wall cold and condensation

Bay external facets cold bridges — mould risk behind furniture. Ventilate bay, consider insulated plasterboard lining before panelling if mould history.

MR MDF does not fix cold wall condensation alone — airflow and heating matter.

Do not panel over active damp — fix source first.

Street-facing presentation

Interior grid visible through window at night with LED — consider uniform colour facets. Daytime symmetry pleases from kerb if curtains open.

Listed bay windows — external alter restrictions do not block internal panelling usually.

Deep window board scribed to bottom rail if panelling wraps under sill return.

Sequencing install around bay

Centre facet first establishes datum — level bottom rail continuous where possible around bay footprint on floor plane even if wall facets angle.

Returns second meeting centre stiles — adjust scribe.

Caulk paintable at facet joints after full bay ring complete.

Typical three-sided bay worked example

Centre facet 1800 mm wide, returns 600 mm each, sill height 900 mm, panelling below sill only. Centre facet shakerpanel.com: width 1800, height 850, four columns two rows, 70 mm strips. Returns: width 600, same row count, two columns — stile at bay corner shared visually.

Corner angle 135° measured with digital protractor — each return stile scribed not mitred to centre stile if walls out of plane.

Radiator in centre facet 1200 mm wide — frame with stiles either side, horizontal rail at rad top, partial panel fields above rail only.

Total sheet count often two 9 mm sheets for whole bay below sill — nest returns and centre cuts on same sheet if lengths allow.

Front elevation kerb appeal

Interior grid visible through bay at night with table lamp — uniform paint colour across facets avoids patchwork glow. Daytime: exterior UPVC frame colour unrelated to interior shaker paint — do not confuse decisions.

Net curtains inside recess do not conflict with panelling below sill. Full-height bay dressings need clearance from top rail if papered above.

Listed conservation area: internal panelling usually permitted without external consent — confirm if bay involves external sill alteration (not typical for shaker strips).

Trickle vents in bay window frame must remain clear — do not panel over vent grilles on returns.