Metal Roofing

Can Metal Go Over Existing Shingles? — Seasonal Guide

September 16, 2028 · Roofing Expert

The short list that adds years to a metal roof in the Valley, and the jobs that are pure theatre.

Roof maintenance in the San Fernando Valley is not complicated, but it is specific, and the parts people skip are the parts that matter. This is what is worth doing on a metal roof, and what is safe to leave alone.

What actually matters

A metal roof is a system rather than a covering. Gauge, coating and fixing method decide how it ages, and none of the three is visible from the ground on the day it goes on. Maintenance on it is therefore about the parts that move, drain or seal, not the parts that merely look worn.

The detail that is usually left out

Timing matters more than frequency. One visit in late autumn, before the first rain, catches the things that actually matter. Thermal movement is the detail that decides everything. A long panel in this climate grows and shrinks measurably between a July afternoon and the following dawn, and a fixing system that does not allow for that movement will fight it until something gives. None of it is complicated, and all of it is cheaper than the call it prevents.

What is specific to the San Fernando Valley

Summer is the problem here. The Valley runs ten to fifteen degrees hotter than the coast and holds it for weeks, so a roof surface that reads 90 degrees in Santa Monica is well past 160 in Van Nuys by mid-afternoon. Everything on the roof expands into that heat and contracts again overnight, and it is that daily movement, not the peak temperature, that opens laps and backs fasteners out. Most of the housing went up between 1950 and 1975, which means original decking, undersized ventilation and at least one previous layer that somebody roofed straight over rather than tearing off.

The full inspection list

Fastener condition on any exposed-fix section, including washer hardening
Clip engagement and any sign of thermal binding along standing seams
Seam integrity down the full run, not only at the visible ends
Coating condition, with particular attention to cut edges and scratches
Sealant at penetrations, end laps and every transition
Panel oil-canning, which is cosmetic but can point to fixing problems
Corrosion at eaves, cut edges and any point where dissimilar metals meet

Common questions

How often should this be looked at?

Twice a year is ideal, and once is enough if you pick the right time: late autumn, before the first rain, catches the things that matter.

Can I do any of it myself?

The ground-level checks, yes. Anything that requires being on the roof is worth handing over, both for your safety and because damage caused by walking on a roof is a common and avoidable expense.

The honest summary

Metal is the longest-lived option available here, but only if the fixing system suits the movement. Ask how the panels are held down before you ask what they cost. In the San Fernando Valley the thing to watch is attic temperature and intake ventilation, because a Valley attic that cannot breathe cooks the underside of the roof as hard as the sun cooks the top.

Want this looked at properly?

Free inspection, drone photography where access is difficult, and a written estimate with deck repair priced per sheet. No obligation.

Call (818) 277-6626 Book a Free Inspection