The 30-second version
- The FCM is Velux's fixed curb-mounted skylight — the most-installed skylight on Los Angeles flat-roof homes.
- Roof pitch range: 0°–60° (works on truly flat roofs, unlike deck-mounted models).
- 21 standard sizes from 14"×33" (size 1430) up to 49"×75" (size 4672), plus custom sizes available.
- Only Velux fixed skylight that offers triple-pane glass as an option (Special Order).
- LA typical: mid-century modern flat-roof homes across Cal Heights, Culver Crest, Silver Lake, Culver City, and the pre-fire Palisades stock.
What the FCM is designed for
The FCM sits on a site-built wood curb — a rectangular frame typically 4"–6" tall, built from standard 2× lumber and attached to the roof around the rough opening. The skylight bolts to the curb, and a curb-mount flashing kit (Velux ECL for shingle roofs, ECW for tile) seals the perimeter.
The reason to spec FCM over a deck-mounted fixed FS:
- Works on flat roofs. Deck-mounted skylights require a minimum 3:12 pitch (14°) to shed water. FCM works from 0° pitch upward. If your roof is truly flat, FCM is often your only option in the Velux fixed lineup (or its larger sibling, the GSM SkyMax).
- Replaces old skylights easily. Most legacy dome skylights on LA mid-century homes sit on wood curbs — the existing curb can often be reused for the FCM (with inspection), keeping install time and cost down.
- Larger sizes than deck-mounted. FCM tops out at 49"×75" standard, with custom sizes going considerably larger. Deck-mounted stops at 44"×46".
- Triple-pane glass option. The only Velux fixed skylight with a triple-pane special-order option for maximum thermal performance (though this precludes the solar shade upgrade).
Standard sizes
FCM sizes are named by outside curb dimensions in inches:
- 1430: 17.5"×33.5" — narrow small
- 1446: 17.5"×49.5" — narrow tall
- 1943: 22.5"×46.5"
- 2222: 25.5"×25.5" — square small
- 2230 / 2234 / 2246 / 2270: 25.5" wide, various heights
- 2347: 26.5"×50.5"
- 3030 / 3046 / 3055: 33.5"×33.5" up to 33.5"×58.5"
- 3171: 35"×75" — narrow largest standard
- 3422 / 3434 / 3446: 37.5" wide, various heights
- 3737: 40.5"×40.5"
- 4622 / 4630 / 4646 / 4672: 49.5" wide, various heights (4672 is the largest standard at 49.5"×75")
Custom sizes are available as a factory order — this is a major FCM advantage for architect-specified projects where a specific opening dimension is required.
Sizing note: the shade is not available for FCM sizes 1430 or 1446 (per the 2026 catalog). If you want the integrated solar-powered shade, spec 1943 or larger.
Glass options
Base FCM ships with double-pane laminated LowE³ safety glass. Special-order upgrades:
- Impact Glass: hurricane-rated laminated. Stocked in sizes 2222, 2234, 2246, 3030, 3046, 3434, 4646.
- White Laminated Glass: internal interlayer diffuses direct sunlight — reduces glare on TV/computer areas below.
- Triple-Pane Glass: the highest thermal performance option. Available in standard sizes excluding 2270, 3055, 3171, and 4672. Note: triple-pane FCM cannot accommodate the solar shade upgrade due to weight/motor clearance.
Where FCM belongs — and doesn't
Right applications:
- Flat or low-slope roofs (0°–15°) — mid-century modern, contemporary flat-roof, torch-down membrane, TPO, PVC
- Replacing an aging dome skylight on an existing curb (60%+ of curbs can be reused with inspection)
- Kitchens, great rooms, and living areas where large-format daylight is the goal
- Architect-specified projects requiring a specific non-standard size (custom-order FCM)
- Regions with high heat load where triple-pane glass helps reduce cooling energy
Wrong applications:
- Pitched roofs above 15° — deck-mounted (FS) or self-flashed (QPF) gives cleaner installation
- Roofs truly flat and > 35 sqft — spec the GSM SkyMax or FXG instead
- Where venting is needed — spec the VCS / VCE / VCM venting equivalents in the same size chart
- Tight interior rooms with no exterior wall — spec Sun Tunnels instead
LA-installed cost ranges (2026)
Typical installed prices in the Greater Los Angeles market for FCM projects — includes skylight, ECL/ECW flashing kit, curb construction (or curb reuse if applicable), roof cutout and sealing, and permit coordination.
- FCM 2222 (25.5"×25.5", base glass): $1,800–$3,000 installed on an existing curb
- FCM 2246 (25.5"×49.5", base glass): $2,200–$3,900 installed
- FCM 3046 (33.5"×49.5", base glass): $2,600–$4,600 installed
- FCM 4646 (49.5"×49.5", base glass): $3,400–$6,000 installed
- FCM 4672 (49.5"×75", largest standard): $4,800–$8,500 installed
- Custom-sized FCM: quote-based; typically starts at $5,500 installed
- Add triple-pane glass: +$400–$900 per skylight
- Add impact glass: +$300–$700 per skylight
- Add interior drywall light shaft: +$1,500–$4,000 per skylight (flat ceilings only)
Warranty
FCM installed with Velux ECL or ECW flashing carries the 10-year Velux installation warranty, 20-year glass seal warranty, 10-year product warranty, and 5-year warranty on shades and controls. Installing without genuine Velux flashing voids the installation warranty.
Get a free Velux quote for your LA home
Halo Build Co is a Velux-authorized dealer serving the Greater Los Angeles area. Every quote includes site inspection, skylight sizing recommendations, cutout and flashing details, and total installed cost — no hidden fees. Text, call, or fill out the form.