The weak points of a steel carport on Guam are at its ends, not in the middle of the frame. The bolts, the base of the posts and the joint where the canopy meets the building are where salt air gets in first and where wind pulls hardest. That is where the work goes.
What the air does to the steel
Salt-laden air and year-round humidity keep steel damp and salty. Bare steel rusts, the rust flakes off, and the section gets thinner. Thinning in the middle of a beam is slow to matter. At a bolt hole it matters sooner, because there was less metal to begin with.
The trouble starts at cut ends, drilled holes and welds, because that is where the coating is broken or was never there. We cut and drill before the steel is coated where the design allows, and a cut made on site gets cleaned and coated again, not left bare.
Galvanising, coating and fixings
Hot-dip galvanising is not paint. The zinc bonds to the steel and goes on protecting it where the surface is scratched. A colour finish goes over the galvanising, not instead of it. Hollow sections get sealed or drained, because a tube that fills with rainwater and cannot empty rusts from the inside.
Fixings get the same treatment as the frame. A galvanised structure bolted together with plain untreated hardware rusts at the bolts, and the bolts hold it down. We use galvanised or stainless fasteners, and keep unlike metals apart where the detail allows: two different metals in contact in salt air set up a cell, and the less noble one goes first.
The footing and the connection matter more than the section
Start with post size and you have started in the wrong place. A heavy post anchored into a thin slab edge is weaker than a modest post on a proper footing. The load travels from the roof, down the post and into the ground, and the weakest step in that path decides how it behaves.
So we look at what the post will stand on: a footing, or a slab poured to carry a car. Where a canopy ties into the house we fix to structure, not to fascia board, trim or a thin outer skin. A connection into something never meant to carry load is the part that lets go.
Why wind finds it first
In still air a carport carries its own weight straight down. Wind reverses that. Air moving across the roof lifts it, so the frame is pulled up and pushed sideways instead. Connections that were in compression go into tension, and gravity stops helping. That is how a structure that stood for years can go in one afternoon.
Uplift is carried by the fixings and the footing, not by how heavy the frame looks. Sheets held down at close spacing, purlins tied to the frame, frame tied to the anchors, anchors set in sound concrete. Typhoon Mawar passed over Guam in May 2023. Wind here is not an unusual event. It is a condition of the site.
What to look at on the one you already have
- Rust streaks running down from bolt heads, or bolts that have lost their coating
- Rust or staining at the base of the posts, where water sits after rain
- Roof screws that have backed out, and washers that are cracked or missing
- Cracked or spalled concrete around the anchors
- Anywhere the structure is fixed to fascia or trim instead of framing
If you want a carport, a patio cover or a canopy over an entry, we will come and look at where it has to stand before anyone talks steel sizes. A carport is a structure, so ask the permit office what your job needs. The walkthrough and the estimate are free, and we work island-wide.
