How To Install Metal Roofing In San Antonio: A Step-By-Step Guide For Homeowners

Every successful metal roof installation in San Antonio starts on paper, not on the roof. Before a single panel is ordered or a fastener is purchased, you need accurate measurements of every roof plane, a clear decision on which panel system to use, and a material list that accounts for waste, trim, and overlap. Ordering short means project delays. Ordering the wrong panel profile means you cannot complete the system as designed.

Measure every roof plane separately. For each plane, measure the horizontal run (width along the eave) and the rake length (the sloped measurement from eave to ridge). Multiply these to get the square footage of each plane, then add all planes together for the total roof area. Always add 10% to 15% for waste, cuts, and trim overlaps. A roofing square equals 100 square feet your supplier will quote materials in squares.

Measure all penetrations and edges. Count every linear foot of ridge, hip, rake edge, valley, eave edge, and any penetration (chimney, pipe, skylight, HVAC curb). These measurements drive your trim and flashing orders, which are separate line items from your panel order.

Choose your panel system before ordering anything. The three most common metal roofing systems installed on San Antonio homes are standing seam, exposed-fastener corrugated panels, and exposed-fastener ribbed panels (sometimes called R-panel or PBR panel). Each system has different installation requirements, different trim components, and different fastener patterns. You cannot mix components between systems.

Order materials with lead time in mind. Custom-length standing seam panels and specialty colors are typically cut to order and can take two to three weeks for delivery in the San Antonio market. Standard corrugated and R-panel in common colors (Galvalume, classic bronze, charcoal, terra cotta) is usually available from local San Antonio suppliers within a few days. Confirm lead times before scheduling your installation crew or starting any tear-off work.

No metal roof performs better than the deck it sits on. Before any underlayment goes down, the existing deck needs to be inspected thoroughly. Soft spots, delaminated plywood or OSB, rotted areas around old penetrations, and any sections where moisture has been sitting under the previous roof all need to be addressed before the new roof goes on. Installing over a compromised deck is one of the most common installation mistakes in San Antonio, and it is one of the most expensive to fix after the fact because it means removing panels to get to the problem.

Underlayment selection matters more on metal roofs than on asphalt roofs. Metal panels expand and contract significantly with temperature changes. In San Antonio, a dark metal roof can swing from 40°F in January to over 160°F in July. That thermal movement means the underlayment must be able to handle sustained heat without degrading, sticking to the underside of the panels, or releasing off-gases that cause the panels to corrode from below. Standard 15-pound felt is not appropriate for metal roofing installations and should not be used under metal panels for this reason.

Before the first metal panel goes up, the trim components at the eave and rake edges must be installed correctly. This step is more important than it looks. The eave trim (also called drip edge or eave flashing) sets the starting edge that every panel will reference. If it is not straight and square to the rake, your panels will drift out of alignment as you work up the slope.

Install eave trim first. The eave trim runs along the bottom edge of each roof plane and gives the first panel a clean edge to sit against. It also directs water off the fascia and into the gutter rather than allowing it to wick back under the panel. Eave trim for metal roofing is typically a formed piece of the same metal as your panels, available in matching colors from your panel supplier. Fasten it to the deck edge at 12-inch intervals using the fasteners specified by the trim manufacturer for your panel gauge.

Snap a layout line before the first panel. Once your eave trim is set, measure up from the eave at two points on the roof plane and snap a chalk line parallel to the eave. This line gives you a visual reference to keep your first panel running square. On most exposed-fastener systems, that first panel sets the alignment for every panel that follows if it is even slightly off square at the bottom, the error compounds all the way to the ridge. Take the time to get this right before you drive a single fastener into a panel.

With your deck prepped, underlayment down, and trim installed, you are ready to install panels. The installation sequence for most metal roofing systems runs from one rake edge to the other across the roof plane, with each panel overlapping the one before it. Direction matters: on most exposed-fastener systems, you start at the rake edge that is prevailing-wind-downwind for your area. In San Antonio, prevailing winds typically run from the south and southeast, so you would generally start at the right rake (west side) when facing the house from the front, and work left.

Overlap depth by system type: Corrugated panels typically overlap by one full corrugation (one rib). R-panel and PBR panel systems overlap at the male rib/female rib joint designed into the panel profile. Standing seam panels snap-lock or clip-lock together at the seam no exposed fasteners through the panel face.

Fastener torque is critical on exposed-fastener systems. The EPDM-gasketed hex-head screw must be driven to the point where the rubber washer is compressed into a slight dome shape, not completely flattened. Over-driving strips the thread, deforms the washer, and creates a leak point immediately. Under-driving leaves a gap between the washer and the panel. Set your drill or impact driver torque before you start and test on a scrap piece of panel.

Fastener placement by system: On corrugated and standard ribbed panels, fasteners go through the flat of the panel, not through the rib. Fastening through the high rib increases the risk of the fastener pulling through under wind uplift. Spacing is typically 12 to 24 inches on center along each purlin or structural member, and at every rib at the eave and ridge rows. Always fasten into structural framing fasteners into decking only are not adequate for wind uplift resistance in Bexar County's wind exposure categories.

Flashing is the most leak-prone element of any roofing system, and metal roofing is no exception. Every place where a panel ends, changes direction, or meets another surface a chimney, a pipe, a valley, a wall, a skylight is a potential water entry point if the flashing is not installed correctly. Flashing work on a metal roof is also more demanding than on an asphalt shingle roof because metal's thermal expansion means flashing details need to accommodate movement over time.

Pipe and vent penetrations use a pipe boot: a preformed flashing collar with a flexible rubber seal that compresses around the pipe. On a metal roof, use a pipe boot designed for metal roofing with a base plate that matches or is compatible with the panel profile. The boot installs over the pipe with the base plate sitting on top of the installed panel. Seal the base plate perimeter to the panel using a urethane or silicone sealant rated for metal roofing standard caulk does not hold up under the temperature swings a San Antonio metal roof experiences. The next panel above overlaps the top edge of the boot base plate.

Chimney flashing on a metal roof follows the same general principle as on a shingle roof but with metal-specific considerations. Step flashing is woven between courses on a shingle roof; on a metal roof, it is replaced with a continuous piece of formed step flashing on each side, custom bent to follow the panel profile. Counter-flashing is embedded into the chimney mortar joint and lapped over the top edge of the step flashing. A proper chimney flashing detail on a metal roof takes time to execute well it is one of the details where cutting corners is most likely to produce a persistent leak.

Valley installation is chosen before your panel order is placed. Open valleys use a formed W-valley strip of matching or complementary metal running the full length of the valley, with panels on both sides trimmed to a clean line away from the center. Closed valleys integrate the panel profiles together at the valley this is more complex to execute but produces a cleaner visual result and is common on premium standing seam installations. Confirm which valley style your crew is planning to use and that your material order includes the correct valley flashing components.

Once all panels are installed and all flashings are complete, the ridge cap closes the roof at the peak. On a gable roof, the ridge cap runs the full length of the ridge from one rake end to the other. On a hip roof, ridge caps run each hip and meet at the peak. Either way, the ridge cap is exposed to full wind load and needs to be fastened securely it is one of the most common components that fails in high-wind events when it was not installed with enough fasteners or the right sealant detail at the panel interface.

Closure strips at the ridge are the first detail before the cap goes on. Foam or rubber closures shaped to match your panel profile are installed at the top edge of the last panel course on each side of the ridge. These closures fill the gap between the panel ribs and the underside of the ridge cap, blocking insects, wind-driven water, and debris from entering the attic space at the ridge line. Do not skip this step an open ridge on a San Antonio home is a direct entry point for everything from rainwater to wasps.

Final inspection covers the entire roof surface systematically. Walk every panel run and look for fasteners that are over-driven, under-driven, or misaligned. Check every flashing detail for gaps in sealant or lifted edges. Confirm that all trim pieces are fully fastened and that no panels have shifted during installation. At the ground level, walk around the perimeter and check for any cut panel edges left untreated, any trim pieces that are not flush, and any debris left on the roof surface that could trap moisture against the panel coating.

After the physical inspection, confirm that your installation is documented for the building permit. The City of San Antonio and Bexar County both require a final inspection sign-off for permitted roofing work. Schedule that inspection before you remove the permit card from the premises. Your contractor should handle this if you hired professional installers confirm it is included in their scope before the job starts, not after it is finished.