Skylights near you

A skylight installation is three jobs stacked on each other. There is the structural one, because cutting through rafters or truss chords is not a matter of reaching for a saw: trusses in particular are engineered components and altering one needs a qualified opinion and often an engineered detail. There is the weatherproofing one, where the unit is set on its upstand and flashed into the roof covering. And there is the internal one, where the shaft is framed, lined, insulated and sealed to the ceiling.

The flashing is where installations succeed or fail. Use the flashing kit made for the unit and for your roof type, since a kit for tile does not work on corrugated sheet and the reverse is equally true. The general rules for any roof penetration still apply: flashings should be purpose made, machine-folded sheet metal sections of material compatible with all upstream and downstream roof covering materials, and metals must be compatible, since the Code prohibits lead upstream of aluminium and zinc coated materials and copper upstream of galvanised coatings, and prohibits lead flashings entirely on any roof that is part of a drinking water catchment area. Sealant belongs as a secondary defence around a properly formed flashing, never as the flashing itself.

The shaft deserves more attention than it usually gets. A shaft is a chimney between your ceiling and your roof: if it is not insulated and sealed, it carries heat into the house in summer, loses it in winter and lets moist household air into the roof space. The building fabric provisions that cap roof light area also account for the shaft in setting the solar heat gain requirement, which is the Code's way of acknowledging that a deep shaft and a shallow one do not behave the same way. Ask how the shaft will be insulated, how it will be sealed at ceiling level, and whether the unit's own performance figures are for the glazing alone or the assembly.

The daylight rule is the flattering one. Because a roof light faces the sky rather than the horizon, the Code asks far less area of it: roof lights open to the sky need an aggregate light transmitting area, measured exclusive of framing members, glazing bars and other obstructions, of not less than 3 per cent of the floor area of the room, where windows must provide 10 per cent. The same 3 per cent test applies where an adjoining room borrows light, calculated on the combined floor area of both rooms. That is why one modest unit can transform a dark room, and why more glass is not automatically better.

The energy rule is the cautionary one, and it pulls the other way. The building fabric provisions limit the total area of roof lights serving a room or space to not more than 5 per cent of the floor area of that room or space, require a Total System U-Value of not more than 3.9, and set the Total System solar heat gain coefficient from a table that varies with the shaft index and the area of the roof light. The total area of roof lights is the combined area of all roof lights serving the room, measured as the area of the roof opening that allows light to enter. Note the state variation: that provision does not apply in New South Wales, so a Sydney installer and a Perth installer are not working to the same requirement.

Put the two together and the design answer for most Australian houses is a modest, well-specified unit rather than a large expanse of glass. An Australian roof takes the full summer sun from above for hours, so solar heat gain is doing more work in your comfort than the U-value in most of the country, and the shaft, any diffuser and any blind are all part of the result. If a supplier quotes you a performance figure, ask whether it is for the whole assembly, and ask what it means for the room in January rather than in July.

Most skylight leaks are not the unit. They are the flashing, the upstand height, or a roof covering detail immediately upslope that sends water into the junction. That is worth knowing because it changes the conversation with an installer: replacing a unit that is leaking at a bad flashing simply buys a new unit with the same leak. Ask for the water path to be demonstrated, testing low first and progressively higher, before anyone quotes a replacement.

The second complaint is water that is not a leak at all. A glazed surface high in a room is a cold surface on a winter morning through June to August, and moisture-laden air from cooking, showering and drying clothes rises to meet it. The result runs down the shaft and looks exactly like a roof leak, but it appears without rain and is worst on the coldest, clearest mornings. The Code's condensation provisions attack this from the ventilation side, requiring exhaust from a kitchen, range hood, bathroom, sanitary compartment or laundry to discharge directly or through a shaft or duct to outdoor air, and requiring roof spaces in the colder climate zones to be ventilated to outdoor air through evenly distributed openings while maintaining a height of not less than 20 millimetres. Extraction that actually reaches outside does more for a sweating skylight than any amount of sealant.

The third issue is bushfire, and it deserves to be stated plainly. On designated bushfire prone land a house and its associated Class 10a buildings and decks must be designed and constructed to reduce the risk of ignition from a bushfire, appropriate to the potential for ignition caused by burning embers, radiant heat or flame, with the deemed-to-satisfy path being AS 3959 at the assessed bushfire attack level or the NASH steel framed construction standard for bushfire areas. A roof light is an opening in the roof plane and a penetration through it, and openings and the gaps around them are precisely where embers get in. Establish the bushfire attack level for the address before choosing a unit, because retrofitting compliance around an installed skylight rarely works.

Skylight installation is unusual in that it sits inside several trade definitions at once, which is why homeowners get contradictory answers. In New South Wales, roof plumbing covers fixing, installing, renovating, altering, repairing and maintaining guttering, downpipes, roof flashing and roof coverings, and the definition expressly extends to putting in skylights, ventilators and the like. A contractor licence is required once the work passes the value threshold in the Home Building Act, and that Act carries substantial penalties for contracting without one. Note the same definition excludes work on non-metallic tiles, glass, concrete, timber products, thatching and bituminous membrane materials, so the covering your roof is made of affects which licence is in play.

In Queensland the QBCC divides it two ways. The roof tiling trade class covers cutting and fixing roof tiles and shingles and shakes, setting out and fixing battens, bedding, pointing and installing associated flashing, safety mesh, sarking and anti-ponding boards, and expressly includes installing skylights. The roof and wall cladding class, which covers roof cladding other than terracotta and concrete tiles, expressly covers flashing penetrations through roofs and walls, including for example installing skylights and ventilators. So a tiled roof and a sheet roof point you at different licence classes for the same product. A QBCC licence is required for building work above its value threshold. In Western Australia, only a registered building practitioner or registered building contractor may carry out particular building work under the Building Services (Registration) Act 2011, with the Building Services Board as the registration authority supported by Building and Energy.

Whether you need an approval is a separate, local question. Replacing a unit in an existing opening is usually maintenance. Cutting a new opening is structural work on the roof, and on a heritage property, in a character area or on bushfire prone land the answer can change again. Your council or a registered building surveyor decides it for your address. LokalMatch is the part before that: you describe the skylight job once, saying whether the roof is tile or sheet, how many storeys, whether it is a new opening or a replacement, and whether there is a roof space and shaft to get through, and matched installers, roofers and roof plumbers come back to you. They pay for those requests. LokalMatch installs nothing, sets no prices, and does not vet, rank or recommend any business, so checking the licence class against your roof covering is a step only you can take.

Australian seasons run the opposite way to the northern hemisphere, and skylights make that obvious. Summer is December through February, and that is when a roof light takes the sun from almost directly overhead for hours at a stretch, with no eave or awning to shade it the way a window has. A unit that is delightful in July can overheat a room in January, which is why the solar heat gain figure, any blind or diffuser, and the ability to open the unit and let hot air out all matter more here than the raw glazing area.

Winter, June through August, brings the opposite complaint. The glass is the coldest surface in the room on a clear morning, so condensation forms there first and runs down the shaft. The fix is ventilation and extraction rather than sealing: get bathroom and kitchen exhaust discharging to outdoor air rather than into the roof space, and use an opening unit where you have one.

Time the work to the weather that tests it. In the south, get installation and flashing work done before the winter and spring fronts, which means booking in autumn, across March to May, not in September. In the tropical north, finish before the wet season arrives around October, since nobody is cutting a new hole in a roof in a downpour. On bushfire prone land, have any roof penetration work and the gutter and roof clearing finished well before your district's fire season begins.