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Five inch, six inch, and the number that actually matters
Most overflowing gutters are not undersized. They are under-drained, back-pitched, or full.
This works out an answer as you change the controls, which needs JavaScript. Without it, the reference section below covers the same ground, and we are happy to talk it through.
Why downspouts matter more than size
A gutter is a holding trough on the way to a downspout. Once water arrives faster than the outlets can take it away, the trough fills and the surplus goes over the front edge regardless of whether it is five inches or six. Adding an outlet is usually cheaper and always more effective than replacing a run.
- Put outlets at the ends of runs, and add one wherever a valley discharges into the gutter.
- A valley concentrates two planes of water into a few feet of trough. That is the spot that overflows first.
- Downspouts need somewhere to go. A downspout discharging against the slab repeatedly wets and dries the clay under one corner of the house, and that soil moves.
- Check the pitch of the run. Gutters hung flat or back-pitched hold water, and standing water is what pulls a run off a fascia.
When the answer is not a bigger gutter
| What you see | What it usually is | What fixes it |
|---|---|---|
| Overflow at one spot every time | A valley discharging into a run with no outlet near it | An outlet where the water arrives |
| Overflow along the whole run | Too few downspouts, or blocked ones | More outlets, or clearing the ones you have |
| Water behind the gutter | Missing or reversed drip edge | Correct edge metal at the eave |
| A sagging run | A rotten fascia that will not hold a spike | Carpentry first, gutter second |
| Water pooling at one corner of the slab after every storm | A downspout discharging against the house | An extension or a buried line that finishes well clear of the foundation |
| A buried line that backs up out of the top of the downspout | The underground run is blocked or collapsed | Clearing or replacing the line; the gutter above it is not the problem |
Sizing is half the question on a Gulf Coast house. The other half is where the water goes once the gutter has caught it: most of this metro sits on a slab over clay that shrinks and swells with moisture, and a downspout soaking the same corner of the foundation every time it rains is doing more damage than an overflowing trough would. Get the discharge clear of the house before spending anything on a bigger gutter.
Gutters, fascia and drip edge are one system, and they are usually diagnosed together.
Have them looked atAll 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.