4x4 Commercial Skylights

A 4x4 skylight is a nominal 4 ft x 4 ft unit. The nominal size is a label, not a measurement: each brand builds its 4x4 skylight to fit a specific curb, so the outside dimension of the curb decides what fits. We carry 9 4x4 skylights. By outside curb dimension, 7 fit a 51 x 51 in. curb; 2 fit a 50 x 50 in. curb.

Measure the outside of the existing curb in both directions, to the nearest 1/8 in., before you choose a unit. If the curb is new, pick the skylight first and order the matching curb below.

4x4 skylights

Brand	Model	Glazing	Fits curb OD (in.)	U-factor	VLT	Hail rating	Matching curbs
Birdview	4848 TBCM	Acrylic or Polycarbonate	51 x 51	.73	.7-.84	n/a	4 on this page
Birdview	4848 TBCM HVHZ	Polycarbonate	51 x 51	n/a	n/a	n/a	4 on this page
Kingspan	4848 KT11 CT 3 WPC CPP C16 MF	White Monolithic Polycarbonate over Clear Prismatic Polycarbonate over Clear 16mm Multi-wall Polycarbonate	51 x 51	.44	.29	n/a	4 on this page
Kingspan	4848 KT11 CT 3 WPC WPP C16 MF	White Monolithic Polycarbonate over White Prismatic Polycarbonate over Clear 16mm Multi-wall Polycarbonate	51 x 51	.44	.27	n/a	4 on this page
Sunoptics	SMD 4040 C2W1 FMRTG	Clear Prismatic Polycarbonate over White Prismatic Polycarbonate	50 x 50	.72	.67	2"	2 on this page
Sunoptics	SMD 4040 C3W0 HVHZ	Clear Prismatic Polycarbonate over White Prismatic Acrylic	50 x 50	.72	.67	2"	2 on this page
VELUX	CMD2 4848 P1C2	See product page	51 x 51	.65	.62	2"	4 on this page
VELUX	CMD2 4848 P1P1	Clear Smooth Polycarbonate over Clear Smooth Polycarbonate	51 x 51	.73	.62	2"	4 on this page
VELUX	CMD2 4848 X1P2	Clear Smooth Polycarbonate over White Polycarbonate	51 x 51	.65	.66	2"	4 on this page

U-factor, VLT and hail rating come from each product page (n/a = not published for that model). Full specifications, cut sheets and 3-part specs are on each product page.

4x4 smoke vents

Brand	Model	Type	Fits curb OD (in.)
VELUX	CSOS 4848 7A1S2	Shrink-Out Smoke Vent	51 x 51

4x4 roof curbs

A curb fits a skylight when its outside dimension matches the skylight's “fits curb OD” within 1/2 in.

Brand	Model	Type	Inside curb (in.)	Outside curb (in.)
AES	4040 ARC3 12H 14GA SSG	Pre-Insulated Roof Curb	47 x 47	50 x 50
AES	4848 ARC6 12H 14GA CG	Roof Curb with Safety Screen	48 x 48	51.5 x 51.5
AES	4848 ARC6 14H 18GA CG	Roof Curb with Safety Screen	48 x 48	51.5 x 51.5
Curbs Plus	CPC-3 4040 12H 14GA 6OC	Curbs Plus Roof Curb	47 x 47	50 x 50
Curbs Plus	CPC-3 4848 12H 18GA 4OC	Curbs Plus Roof Curb	48 x 48	51 x 51
Curbs Plus	CPC-4 4848 14H 18GA 4OC	Curbs Plus Roof Curb	48 x 48	51 x 51

4x4 fall protection (screens, cages and guards)

Skylights on a roof where people work need fall protection under OSHA. Interior screens drop inside the curb; exterior screens and cages go over the unit. See the skylight screen guide for how to choose.

Brand	Model	Mounts	Curb dimension on product page (in.)
Curbs Plus	CP 4848 ZFRAME 4OC	Inside the curb	ICD 47.5 x 47.5
Kingspan	4848 SSCRN	Inside the curb	ICD 48 x 48
Sunoptics	ESFP 4040 W51.250 L51.250	Over the unit	OCD 50.25 x 50.25
Sunoptics	GUARD 4040 W47 L47 CLPOG	Inside the curb	ICD 47 x 47
VELUX	CAE 4848 0004	Over the unit	ICD 52 x 53.5

Need help matching a unit to your curbs? Send us the outside curb dimension and quantity and we will quote the skylights, curbs and fall protection together.
Request a skylight quote All quote forms or call 1-844-455-7283