We size gutters to fit the roof

Commercial roofs need bigger gutters and downspouts

A plaza or warehouse roof collects rain across a far wider surface than a house, and all of it heads for the same edge. A regular house gutter fills up in the first minutes of a summer storm and spills over the front edge. That water comes down along the wall and pools at the foot of the building. So a commercial job starts with the roof itself: how much area drains to each side, and where that water has to end up.

Box gutters and four by five downspouts are built to carry that much water. The two have to be matched. A big gutter feeding a small outlet still backs up, because a gutter only drains as fast as the pipe below it. A big downspout under an undersized gutter never gets the chance to work, since the water spills over the edge first. We work out the gutter and the downspouts together, as one system.

Around Oldsmar and Clearwater, many commercial buildings are concrete block with stucco, often with low-slope roofs that drain to one or two edges. Metal buildings show up in the industrial areas. Each one needs a different way of mounting the gutter. On block, the gutter fastens to a fascia board that has to be solid first. On a metal building, it follows the eave line of the roof panels. Either way, the gutter has to line up with where the water actually leaves the roof.

• Box gutters for large commercial roofs
• Four by five downspouts for heavy flow
• K-style runs formed in one length
• Hidden hangers along the full eave
• Fascia checked and repaired before install

Box gutters carry what standard gutters cannot

The shape does most of the work. A box gutter has straight sides and a flat bottom, so none of its depth is lost to a shaped front. On a long commercial eave, that extra room is the difference between water going down the pipes and water sheeting over the edge. It also looks plain and square, which suits the straight lines of a block building or a warehouse wall.

Long eaves bring a second problem. Eaves on a plaza or warehouse run long, and every joint in a gutter can leak once its sealant bakes in the sun. Not every building needs a box gutter, either. Many take a large K-style gutter formed in one continuous length on site, which leaves joints only at the corners. Corners are closed with strip miters or bay miters, and a corner that was not sealed right is where a long run leaks first.

On a long box gutter, the hangers matter as much as the gutter itself. A full gutter on a long eave is heavy, and hangers spaced too far apart let it bow in the middle. Once it bows, water sits in the low spot instead of running to the outlet. A gutter that holds standing water leaks at its seams sooner. Hidden hangers set close together along the fascia hold the gutter at its pitch toward each downspout from end to end.

Florida storms test every commercial gutter

Summer rain around Oldsmar arrives in short, heavy afternoon storms on many days from late spring into fall. A commercial gutter has to handle the heaviest part of that storm. When the box gutter or the downspouts are too small, the overflow lands in the same spot every time. On a lot of plazas that spot is the front walk, where it leaves a slick patch and a stained wall above it.

Wind brings the other kind of damage. Tropical storms push rain sideways and pull at anything loose on a roof edge. Hurricane season overlaps the rainy months, so wind and heavy rain often arrive together. A long gutter on weak hangers or rotted fascia can peel off in one storm and take trim with it. So we check the fascia before a new gutter goes up, and soft wood gets replaced first.

Near the water, salt does slower damage. Buildings close to the shore in Clearwater and Dunedin get salt carried in on the breeze, and it settles on every gutter. Salt goes after fasteners and cut metal edges first. Aluminum holds up well, but a plain steel screw or a joint between two different metals will corrode and stain the stucco below it. Fasteners that match the gutter metal keep rust streaks off a clean wall.

We schedule around other trades on site

A commercial gutter job rarely happens on its own. It usually lands in the middle of a roof job or a repaint, and the order of the work matters. Gutters go up after the roof edge is done and the fascia is painted. When that order slips, somebody pulls off brand new work to fix the step under it. On a plaza, that can mean taking down a finished gutter so a roofer can reach the edge.

We work out the scope and the schedule with you before anyone climbs a ladder. We find out who else is working on the building. Then we plan where each downspout can come down without blocking a door. On a busy commercial site, that planning keeps the gutters from holding up anyone else. Greg Avis put it this way in a Google review: "Worked with me on the scope of work and schedule of other trades."

Sometimes the trouble starts above the gutter. A box gutter can overflow because a roof edge pitches the wrong way. It can also overflow because the fascia behind it has rotted. When that is the case, you should hear it at the estimate. A new gutter hung on a bad roof edge only moves the leak somewhere else. One customer, M F, wrote that Blair "accurately identified the project's complexity and recommended involving a roofer to ensure a long-term solution."