The short answer
Sagging usually means hangers have pulled or spacing was too wide — a cheap fix unless the fascia behind has gone soft. Leaking seams and corners are usually sealant, also cheap. What isn’t repairable is a channel that has rusted through or split along its length, or any fault where the timber it hangs from has rotted. That last one is the actual job; the gutter is just where you noticed it.
Sagging
Hangers, usually
Leaking joint
Sealant, usually
Rusted through
Replace the section
Soft fascia
The real repair
What kind of fault is it?
Four common symptoms, and what each one actually means.
Cheap fix
A dip in the run
Hangers have pulled loose or were spaced too far apart. Refixing or adding hangers solves it, provided the fascia is still solid behind them.
Cheap fix
Dripping at a joint
Sealant has aged out at a seam, corner or outlet. Clean back and reseal. On sectional systems this is routine maintenance rather than damage.
Section replacement
Rust holes or a split
Steel that has rusted through, or aluminium split along a crease. Patching buys a season. The section needs replacing.
Bigger job
Soft or stained fascia
The timber the gutter hangs from has been getting wet, probably for years. New hangers won’t hold in it. The gutter is a symptom — the fascia is the repair.
The fault that isn’t a fault
Water overflowing in the same place every storm, on a gutter that is clean and undamaged, is not a repair problem. It is either pitch — the channel is holding water at that point rather than moving it — or capacity, meaning the system is too small or has too few downspouts for the roof.
Both get misdiagnosed as damage and repaired repeatedly. Neither is fixed by sealant or hangers. If a company has resealed the same corner twice, ask them to check the fall with a level and to tell you the roof area and downspout count.
Working out what you’re dealing with
From the ground, with a hose, before anyone quotes.
Watch it during rain
Where does it overflow, and does it happen every time or only in downpours? Every time points at pitch or a blockage; only in heavy rain points at capacity.
Look along the run
From the end, at eye level if you can. A dip is obvious from that angle and invisible from below.
Run a hose from the far end
Watch where water pools rather than moves. A standing puddle marks the low point.
Check the fascia
Press it where it’s stained. Any give means the timber is the job, whatever the gutter is doing.
Count the downspouts
One on a long run of heavy roof is a capacity problem no repair will solve.
What’s worth repairing
Where this stops being a DIY job
Soft fascia. New hangers screwed into rotten timber will pull out, usually within a year, and can take the board and part of the soffit with them. That is a carpentry job that has to happen before any gutter work, and it is not something to discover halfway up a ladder.
Any repair above single storey. Repair work is worse than cleaning at height — both hands occupied, tools, and a length of gutter to hold level.
Repeated overflow in the same place after two repairs. It isn’t a repair problem. Someone needs to check the fall and the sizing rather than reseal it a third time.
Signs of a diagnosis rather than a patch
Checks
Puts a level on it
Before quoting a repair. Half of what gets called damage is fall.
Probes
Tests the fascia
Any give and the conversation changes. A company that skips this is quoting for the wrong job.
Counts
Looks at the downspouts
Because repeated overflow on an undamaged run is usually capacity, not damage.
Common questions
Why do my gutters sag?
Hangers have pulled loose or were spaced too widely to begin with. It’s a cheap fix — unless the fascia they screw into has softened, in which case the timber has to be repaired first.
Can leaking gutter seams be repaired?
Usually yes. Clean the joint back and reseal it. On sectional systems this is normal maintenance rather than damage, and it recurs every several years.
When should gutters be replaced instead of repaired?
When the channel has rusted through or split along its length, when several sections are failing at once, or when the system is undersized for the roof and overflows however clean it is.
Why does one corner always overflow?
Pitch. The channel is holding water at that point rather than carrying it to the outlet. Resealing won’t change it — that section needs re-hanging with the correct fall.
Same fault twice, or timber giving behind the gutter?
Watching where it overflows, running a hose and pressing the fascia are all free and they tell you which of four jobs you actually have. Soft timber and repeated overflow after repairs are the two that need someone who’ll put a level on it rather than another tube of sealant.
Call (877) 360-4657