Letting in the Light

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“A Clean, Well-Lighted Place” is more than just a good story title, it’s what you’re aiming for in a great barn. And among the features that can help you reach that goal is free light. Daylight, after all, is out there, bouncing around and being wasted, just waiting to brighten the dark corners of your barn. And with a little handyman experience or a helpful person with a saw, you can harvest that sunshine and put it to work.

Skylights mean you don’t have to leave expensive electric lights burning all the time and they add a more welcoming touch of daylight indoors, especially in larger barns. And, skylights offer about five times more light than the average wall window. You’ll also find that new skylight models leak less than older skylights, especially if your work is done right. But, be aware that skylights don’t work for everything—obviously you won’t get a lot of benefit on dim, cloudy days.

The number of skylights to install depends on the size of the barn. A good rule of thumb says to use a 1:20 skylight to floor ratio for proper lighting. That means a 24” x 48” skylight will light up 160 square feet of floor, about the size of one 12’ x 12’ stall.

For indoor rings, a combination of skylights and skypanels can work well, where you install skylights along both sides of the ridgepole, and then along the walls, substitute the top three or four feet of wall paneling with acrylic or fiberglass. The side panels, however, are best installed when first building the indoor.

In warm climates, any ventilation needs you haven’t addressed will jump right out at you when you add skylights, since light equals heat. While you’re cutting holes, you’ll want to add large vents at each end of the building, just below the roofline. When combined with a powerful fan that operates via a thermostatically-controlled switch, they remove large volumes of the hot air that collects at the roof’s highest point.

Models to Select

Skylights come in several models, from simple, flat or corrugated sheets of fiberglass to complex, thermostat-controlled self-venting models that operate with a remote control. For a barn, simpler is generally better, especially when you’re not around to close an open skylight when the wind picks up before a storm.

See-through roofing: The basic fiberglass-panel option is a great one, if you have a simple metal panel roof. There’s no major reinforcing required of rafters, braces, etc. You just pull out a metal panel and replace it with the same size fiberglass panel, likely manufactured by the same company that made the metal stuff. Matching the manufacturer is essential though, since the fiberglass panel’s corrugation pattern must exactly match that of your existing panels in order to keep water out.

Clear, frosted or lightly colored fiberglass will cost you about $10 to $15 per panel for 8-foot or 12-foot lengths, plus nails. Using roof mastic or high-quality silicone sealant on the edges and nail or screw heads is a must if you want to be certain the job is weatherproof. You are limited, however, to placing these panels exactly where the original metal panel was, so there’s a little less flexibility in centering the light over the wash stall, tack room or other areas of particular interest.

Serious skylights: Manufacturers across the country have created a huge range of professionally designed skylights for every roof type and situation, many of which can be found at your local builder’s supply or home hardware store. A quick search on the Internet for “skylights” will also produce dozens of manufacturers and distributors who will ship you a prefabricated skylight or one tailored to your exact needs. You’re looking at spending $150 to $500 or more per unit, depending on size, quality and features.

Prefabricated skylights are built in sizes to fit neatly within standard rafter dimensions so, unless your barn was built with unusual dimensions, you won’t need to chop out rafters and add filler, or “jack” rafters to accommodate odd sizes. Custom skylights cost more, but can be built to accommodate the most peculiar rafter dimensions and roofing material.

Before choosing a model, decide whether to buy a skylight panel with a single layer of glass or a double-panel design with dead-air space between. Unless you’re desperately short of cash on this project, buy double-paneled units: they provide better insulation and sometimes have a frosted inner bubble to prevent glare. With a single layer of glass, you’ll get condensation and eventual failure of the skylight, over time.

Flush-mounted skylights resemble flat windows sitting in the roof. The flat skylights can be purchased as self-flashing, meaning that they are edged with metal sheeting that you’ll tuck beneath your roofing tiles or shingles; but most builders recommend that you install regular-step (small, overlapping sections) or sheet flashing instead, tailoring the installation and adhesive application to the roof. But because it’s a lot more difficult to get a good seal on the flush-mounted units, most installers or manufacturers will steer you toward curb-mounted lights.

A curb is a wooden rim projecting above the roof surface, with metal flashing and sealant, onto which you mount the prefabricated skylight. The advantage of the curb-mounted skylight is in waterproofing, as a high curb edge provides a barrier to water flowing down the roof or snow piling up behind the uphill side. The curb, made of two-by-six or two-by-eight lumber, frames the opening in the roof, and the skylight sits neatly down on the top edge of it, secured with metal tabs or screws. Since the skylight itself is not down at roof level, it is not likely to leak and proper flashing around the curb itself will provide a snug, weatherproof edge that will probably last approximately the lifetime of your roof.

Another option is to install operating skylights. These can be hand cranked or electrically opened and closed. While ideal for home use where additional ventilation is needed, they are not necessarily the best choice for a barn. Ventilation is indeed essential in the barn, but the last thing you want is for a high wind to come along while you’re out in the field and tear your open skylights right off the building. Plan, instead, to add vents through a cupola or at either end of the building, preferably with a thermostat-controlled fan.

For enclosed tack rooms or bathrooms with full ceilings, there’s yet another skylight variation that is inexpensive and useful. Tube lights, with a lens at the top and a reflective tube running from the lens to the ceiling panel, can be purchased for well under $200 each, and for small spaces they’re great. Their value lies in the small area of roof to be pierced, plus the tube means you don’t have to install an enclosed, drywall “light well” between an existing ceiling and the roof.

Preparing Your Roof

If your barn is open clear to the rafters, you’ll want to rent a scaffold to work both inside and outside. Teetering on a ladder up in the rafters will get old fast.

Before you climb up, gather your materials. (See sidebar, “Tools of the Trade.”) Then tack a heavy sheet of plastic to the exterior of the roof just above your work area, so you can flip it into place over the hole in case of rain. Back down on the ground, peel off the blue protective plastic from your skylight’s acrylic panels before it melts in the sun and becomes difficult to remove. Then you can locate your rafters, measure the area to be opened and begin the serious work.

From the inside, find the center point of your skylight’s location and using the inside curb measurements of the skylight unit, measure carefully along the inner surface of the roofing and rafters, using a framing square. Place a nail at each corner, projecting through to the outside of the roof, and snap a chalk line from nail to nail. Then snap another chalk line 3 inches above the top and 3 inches below the bottom edges of your marked lines. This makes room for the doubled header boards you’ll install between the intact rafters.

With the circular saw, make two cuts across the rafters on the outer 3-inch lines and remove any cut rafters. Cut only deep enough to cut the rafters, not roof. Now cut four header boards from the same sized lumber to fit exactly across the space between the intact rafters on either side. Nail the first header board along the top cut, nailing through the rafters with 16d nails into the ends of the header board, and nailing through the headers into the ends of any cut rafters. Nail a second header against the first. Repeat on the bottom edge.

Now move to the outside of the roof. From the nails marking the corners, re-measure all edges and snap them with a chalk line. Now snap another chalk line 2 inches from the outside edge of your initial marked square, showing where you’ll cut the shingles back to make room for the flashing. With a circular saw blade set only deep enough to penetrate the shingles, cut along the outer line and peel back the shingles to make just enough room for the flashing. Snap new lines based on your inner square for the interior dimensions of the skylight onto the exposed plywood. Now cut through the roof decking. Lift off the section of decking you’ve sliced free.

A caveat from an experienced builder: In the initial roof cut, during which the roofing and then the panel or roof decking is trimmed away to reveal the rafters, don’t make too roomy a cutting job. Should the plywood decking beneath asphalt shingles, for example, be cut away too freely, the metal flashing placed over the gaps between the decking and the curb edge later will tend to sag and capture damaging water, rather than draining it away.

Now you can take the wooden curb unit that you squared up before you started on the roof and drop it into place. Be sure it’s exactly centered over the roof opening and has good, square corners. Then toenail it into place from its inside surface through the decking to the rafters and headers.

Install the flashing around all the curbing and beneath the shingles using plenty of roof mastic, and put a line of mastic or caulking along the top edge of the curb. Place the skylight down on the curb firmly and nail or screw the skylight down using the factory-drilled holes or tabs. Dab caulking or mastic over the nail heads to finish.

Now go into the barn with a glass of champagne and toast your new lease on light!