Rough-opening framing, curb, flashing, light shaft and cost for a skylight install.
Estimates are planning aids, not a professional quote. Double-check quantities and product coverage — and any local code or permit requirements — before you buy.
⚠ Brace the rafters on both sides of the cut with temporary jack posts before you remove any framing — an unsupported cut lets the roof deck sag or the opening rack out of square.
⚠ Check local code before you cut: most areas require a permit for a new roof penetration, and many require ice-and-water shield around the curb regardless of climate zone since it's the highest-risk leak point on the roof.
| Doors & Windows | $400–$541 |
| Lumber & Decking | $121–$163 |
| Roofing | $64–$86 |
| Drywall | $60–$81 |
| Insulation | $51–$69 |
| Membrane & Fabric | $24–$32 |
| Fasteners & Hardware | $24–$32 |
| Finishing & Sealant | $14–$18 |
| Total | $756–$1,022 |
Excludes tools, delivery, tax and permit fees. Labor not included — this is a DIY materials estimate.
These are affiliate links: we may earn a commission if you buy through them, at no extra cost to you. It never changes what the calculator recommends — the shopping list comes from your dimensions, not from what pays.
About this calculator
Give the Skylight Calculator your rough opening size, roof pitch and how far the roof deck sits above your finished ceiling, and it works out the whole installation: doubled headers and trimmers framed into the cut rafters, a curb kit sized to the opening, step and head flashing matched to your pitch, and — if you're not working under a cathedral ceiling — the light shaft framing, insulation and drywall that carry daylight down through the attic to the room below.
Choose fixed or vented glazing and it prices the unit at the right size tier, then flags a cricket if you've picked a wide skylight on a low-slope roof where debris and water can dam behind the curb. Dial in rafter spacing and lumber size to match your actual framing, and toggle the shaft insulation on or off. This is a planning estimate for a single rectangular skylight — multiple units in a row, box-and-two-slope skylights and load-bearing engineered rafters need a look from a structural pro before you cut.
Step by step
A step-by-step walkthrough to go with your plan above. Follow the product instructions and any local code or permit requirements as you work.
Locate the opening between rafters (call an engineer first if it's a truss roof), confirm it clears any plumbing or wiring in the attic, and mark the cut lines on both the roof deck and the ceiling before you touch a saw.
Brace the rafters on either side of the cut with temporary jack posts before removing any structural framing, then cut through the roof deck and the rafter section and clear the debris.
Install doubled headers above and below the opening and doubled trimmer rafters down each side, sized to your existing rafter depth, so the header carries the load the cut rafter used to.
Fasten the pre-fabricated curb to the framed opening, then flash it with self-adhered underlayment, followed by step flashing up each side and head flashing at the top, shingled to shed water past every seam.
Set the skylight onto the curb per the manufacturer's fastening schedule, and if it's low-slope or wider than about 30 inches, build a cricket behind it first so water doesn't dam against the high side.
If there's an attic between the roof deck and the ceiling, frame the light shaft with studs down to a matching cut-out in the ceiling drywall, and insulate the shaft walls so attic temperature doesn't leak into the room below.
Hang drywall on the shaft walls, tape and mud the seams, and finish with corner bead at each edge so the light well reads as a clean opening rather than a raw framed hole.
Run exterior sealant along the curb-to-flashing transitions and check the whole assembly after the next hard rain — a skylight leak almost always traces back to a flashing lap, not the glass itself.
Equip the job
Hand-picked categories that match the shopping list above. Links open a current selection so you can compare brands and prices.
These are affiliate links: we may earn a commission if you buy through them, at no extra cost to you. It never changes what the calculator recommends — the shopping list comes from your dimensions, not from what pays.
As an Amazon Associate I earn from qualifying purchases. We may also earn from other retailer links here. This doesn’t change your price and helps keep these planners free.
Keep planning
Interior & Finishing
Answers
DIY materials for a single fixed skylight — the unit, curb kit, flashing, rough-opening framing and a modest light shaft — typically land somewhere between $600 and $1,600 depending on size, whether it's vented, and how deep the shaft runs through your attic. A vented, electrically operated unit and a longer shaft push that higher. Hiring a roofer to cut the opening, flash it and finish the shaft usually runs several times the materials cost because it's fall-hazard work through a structural roof cut. This calculator totals materials only, sized to the opening and shaft depth you enter.
The rough opening is framed with doubled headers above and below the cut, and doubled trimmer rafters down each side, all sized to match your existing rafter depth — typically 2×8, 2×10 or 2×12. If the opening is wider than one rafter bay, you're cutting into more than one rafter and the header has to carry that extra load, which most jurisdictions require an engineered beam and a permit to sign off on. This calculator sizes the doubled lumber for a single- or double-bay cut; a wider skylight or a load-bearing truss roof needs a structural engineer's header spec before you touch a saw.
A light shaft is only needed if there's an attic or open framing cavity between the roof deck and your finished ceiling — a skylight set directly into a cathedral ceiling with no attic doesn't need one. Where there is a gap, the shaft is framed with light-gauge studs running from the rough opening down to a matching hole cut in the ceiling drywall, insulated to keep the attic's temperature out of the light well, and finished in drywall like a small closet chase. This calculator sizes that framing, insulation and drywall from the vertical distance you enter between the roof deck and the ceiling plane.
A fixed skylight is sealed glass or acrylic that only lets light through — cheaper, simpler to flash, and the right call for a skylight you can't easily reach to operate. A vented skylight opens manually with a pole or electrically with a remote or rain sensor, and doubles as extra ventilation for a bathroom, kitchen or stuffy upstairs room, but costs more and needs a home run for power if it's motorized. Both use the same curb and flashing kit; the vented unit is simply a pricier line item and, if it's motorized, adds a small low-voltage control kit to the shopping list.
A cricket (a small diverter ridge) is code-required or at least strongly recommended behind any skylight wider than about 30 inches on a roof pitched under 4:12, because water and wind-blown debris collect against the high side of the curb on a shallow slope instead of shedding around it. Steeper roofs and narrower skylights generally don't need one. This calculator flags it when your width and pitch combination crosses that threshold — build the cricket from framing lumber and the same underlayment and flashing already on your shopping list, tied into the field shingles above the curb.