Metal roofing
Metal is a detailing trade, not a material choice
A metal roof that is installed properly outlasts two or three shingle roofs, which in a climate that cooks asphalt is a real argument. A metal roof that is installed like a shingle roof leaks at every penetration within a few years.
The two systems, and what separates them
| Consideration | Standing seam | Exposed fastener |
|---|---|---|
| How panels are fixed | Concealed clips, no penetrations through the water plane in the field | Screws through the panel face with a rubber washer |
| Thermal movement | Clips allow panels to move as they expand and contract | Movement works against a fixed screw, which eventually elongates the hole |
| Maintenance | Almost none in the field; attention goes to flashings and penetrations | Washers harden in ultraviolet and need checking; some screws need replacing over the life of the roof |
| Where it fits here | Main roof planes on houses, coastal property, and anywhere the roof is visible | Outbuildings, barns, shop buildings and porch roofs where the trade-off is understood |
| What it asks of the installer | Accurate layout, correct clip spacing, and flashings fabricated rather than bought off a shelf | Correct screw torque, which sounds trivial and is not |
Where metal genuinely makes sense on a Houston house
- Low-slope sections that shingles cannot cover. Patio covers, rear additions, porch roofs and dormer tops below the minimum slope for asphalt. This is the most common good reason for metal on an otherwise shingled house here.
- Wind exposure. A properly clipped standing seam system with engineered edge detailing is a strong answer to uplift, and on the coast the uplift requirements are not optional — see windstorm cover and TWIA.
- Heat. A reflective finish over a vented assembly puts noticeably less heat into the attic than a dark asphalt roof does, which in a nine-month cooling season is a running cost rather than a comfort preference.
- Long, simple slopes where a standing seam system can run unbroken from ridge to eave with no penetrations to work around.
The coastal question: salt, coatings and fasteners
Distance from salt water changes this decision more than anything else on the page. Salt-laden air accelerates corrosion at every cut edge, every fastener and every dissimilar-metal contact, and a specification that is perfectly sound in Cypress can be the wrong one in Galveston, Seabrook or Surfside.
- Substrate and coating matter more near the water. Ask what the panel substrate is and what the finish system is, and ask specifically how it is expected to behave within sight of salt water.
- Fasteners and clips are part of the corrosion question. Mixing metals at a fastener is how a roof grows rust streaks that have nothing to do with the panels.
- Cut edges and flashings are where it starts. Site-cut panel ends, valleys and wall flashings corrode before the field does.
- Rinsing helps. On coastal property, rain does not reach every surface, and the sheltered areas under eaves and behind flashings are where salt accumulates.
What decides whether it performs
Almost everything that goes wrong with a residential metal roof happens where the metal stops: at the eave, at a wall, at a chimney, at a valley, or at a pipe. Panels in the field of the roof rarely fail. Fabricated flashings, correct clip spacing, allowance for movement, and a plan for every penetration are what the job actually consists of.
Ask to see how the installer intends to detail the valleys and the wall junctions before anything is ordered. If the answer involves sealant as the primary defense rather than as a backup, that is the answer.
The honest trade-offs
- Metal is noisier in rain than shingles over a solid deck, and noticeably so over an open framed patio cover. In a region that gets serious rainfall, that is worth hearing before you buy it.
- Oil-canning — slight waviness in flat panel areas — is a characteristic of the material, not a defect. Striations and heavier gauges reduce it and do not eliminate it.
- Walking on a finished metal roof requires knowing where to step. Anyone who works on the roof afterwards, from a satellite installer to an air conditioning technician, needs to know that.
- A metal roof is a long commitment. If the house is likely to change hands in a few years, the value of that longevity does not all come back to you.
Considering metal for a patio cover, an addition or the whole house?
Request a free inspectionCan metal go over my existing shingles?
It is sometimes done over purlins. It is still hiding a deck nobody has looked at, and it makes any future work on the structure harder. Where a metal roof is worth doing, it is worth doing on a deck that has been seen — and on the coast, a reroof over an uninspected deck is a poor way to approach a windstorm certificate.
Does a metal roof attract lightning?
No. It is not more likely to be struck, and because it is non-combustible and conductive it is generally considered a safer covering in a strike than a combustible one.
Will it dent in hail?
Softer metals and lighter gauges can dent in large hail, and this market does record large hail. The thing to know is that a dent in a metal panel is often cosmetic rather than functional, and that some Texas policies carry a cosmetic damage exclusion that treats it accordingly. Check the declarations page before assuming either way — what to look for.
Does a metal roof make the house cooler?
A reflective finish reduces the heat the roof delivers into the attic, and how much that is worth depends on what is under it: insulation depth, duct location and whether the attic is vented or sealed. It is a real effect and it is not a substitute for insulation.
All work is performed by insured local roofing professionals. Texas does not license roofing contractors at state level, so insurance, references and a written scope are what there is to check.