Your Sunroom Roof Is a Different Roof

Many houses in St. Charles County have a sunroom or screened porch that was added years after the main roof went on. From the driveway it looks like part of the same house. Up close, its roof is often a different assembly: a low pitch, a panel or glass system instead of shingles, and a joint where it meets the older roof that was sealed by hand. When you ask for a quote on the house, that small roof is easy to leave out, and it is the part most likely to leak in the first spring.

This page is for the homeowner who has a sunroom, a glassed porch or a patio enclosure and wants to know what a roofer should check before the price is set. It does not tell you which product to buy. It tells you what to look for and what to have written down.

Panels, glass and what each one ages into

Sunroom roofs in this area are usually built one of three ways. Some have a solid roof of the same shingle as the house on a low slope. Others use glass or tempered panels set in aluminum framing. A third group uses polycarbonate sheets, which are light and inexpensive but yellow and become brittle after years of summer sun. Each material ages differently, so a roof that looks sound today can be on a timeline you cannot see from the ground.

Polycarbonate sheets expand and contract more than glass. In a St. Charles winter, when the temperature drops below freezing overnight and climbs into the forties by afternoon, the sheets move against their fasteners every day. Screws that were tight in the first year can back out, and the rubber washers under them can crack. A roofer who climbs up should check each fastener and each washer, not just the sheets that look cloudy.

Glass panels leak most often at the glazing bead, the strip that holds the pane in its frame. The seal is usually a bead of silicone or a gasket. Both shrink or lose adhesion over time, and water runs along the inside of the frame before it shows as a stain on the ceiling below. If the sunroom has a ceiling, look at the top edge of the ceiling board after a heavy rain.

The joint where the sunroom meets the house

The weakest point on most added roofs is the wall where the new roof meets the old wall. The main house wall was built to shed water down the siding. The sunroom roof was attached to that wall after the fact, and its flashing has to lap over the house's flashing in the right order: the upper edge tucked under the siding or the house's own flashing, and the lower edge over the sunroom's roof. When the order is reversed, water runs behind the flashing and into the wall cavity where nobody sees it.

Ask the roofer to show you this joint before any tear-off. It is a short check from a ladder, and it tells you whether the flashing was installed by someone who understood the wall or by someone who was only matching a color. If there is no flashing at the joint at all, the usual repair is a continuous metal piece that runs the full length of the wall with a drip edge at the bottom. A roofer should be able to name that piece and say where it starts and where it stops.

Ventilation and the condensation nobody expects

An enclosed sunroom traps heat. In July the glass or polycarbonate can push the space well above the outdoor temperature, and in the cold months the warm room air meets a cold roof surface and condenses. The result is dripping along the inside of the frame or under the lower edge of the panels. Homeowners often read this as a leak from above and spend money on the wrong repair.

Check whether the sunroom has any ventilation at all. Some have operable windows or a ridge vent. Some were built with no vent, and the ceiling is a single solid board fastened tight to the rafters. Ask the roofer whether ventilation is part of the scope, and if it is, have the vent type and location written on the proposal. A vent that is added after the roof is finished is much harder to place well.

Condensation in a sunroom also tells you about insulation. If the ceiling is uninsulated, the room will be cold in winter and hot in summer no matter what the roof is made of. That is a separate decision from the roof, but it belongs in the same conversation, because a new roof over an uninsulated ceiling can still sweat.

What freeze and thaw do to a low slope

Most sunroom roofs run at a low pitch, often between two and four in twelve. Water moves slowly across that surface and can sit in any dip. In a St. Louis winter the cycle of thaw and freeze is the biggest problem. Melt runs down the slope during a warm afternoon, reaches the cold lower edge at dusk, and freezes into a ridge of ice. That ice pushes water back up under the shingle or panel edge. This is the same mechanism as ice damming at the eave of a main roof, but on a sunroom it happens faster because there is less slope to clear the water.

If the sunroom has a built-up or rolled roofing surface, look at the lower edge for granule loss and for any bubbling. If it has shingles on a low pitch, the manufacturer's instructions for low-slope use should be on the proposal, and the roofer should say which product and which underlayment they are installing. Do not accept a sentence that says the roof will be installed to standard without naming the standard.

Permits and the enclosed addition

An enclosed sunroom is often treated as an addition, not a porch, and the difference matters to the permit desk. Many municipal offices in St. Louis County ask whether the enclosure was built with a permit, and whether the roof work you are planning changes its structure, its load path or its wall connection. If the sunroom has no permit on file, a roof replacement can bring that question up. Ask the roofer whether they will pull the roof permit where one is required, and ask the municipal desk what it needs for an enclosed roof before the start date is fixed.

Permit rules vary by city and by county, and the exact requirements are for the local desk to state. What you can control is whether the proposal names the permit, names who pulls it, and says whether the sunroom is inside the scope or outside it.

What to have in writing before the sunroom is opened

• The roofing material for the sunroom, by product name, and the underlayment under it.
• The flashing at the wall joint, described as a piece with a start point and an end point, not simply as flashing.
• The fastener type and washer for any polycarbonate or panel section, and whether each washer will be replaced.
• Whether the glazing bead or silicone at the glass or panel frame is part of the job.
• The ventilation plan for the enclosed room, including the location of any new vent.
• Who pulls the permit for the sunroom roof, and whether the sunroom is inside the scope.
• What happens to the ceiling board if the roof is opened and the wood below is wet.

Keys Roofing documents the sunroom roof with photographs and measurements at the start, and puts a written scope with those photos in your hands before the work begins. Keys attends as the contractor on the day of the work. If you have a sunroom and want it looked at on the same visit as the main roof, call (314) 220-2333 and say so when you book.

One question to ask first

Before you compare sunroom roof bids, ask each roofer to show you the wall joint and the fastener at the lowest sheet. Their answer will tell you more about the job than the price line does.