Are my gutters and downspouts causing the wood rot on my house?
Short answer
Often, yes, in one of three ways. A clogged or sagging gutter overflows onto the fascia behind it and down the wall below. A downspout that ends at the foundation or on a deck dumps a roof's worth of water against a post, a ledger or siding. A roof with no gutter creates a drip line that hammers whatever sits under the eave: deck boards, trim, a fence or a pergola beam. Fixing the water path is cheaper than any wood repair.
A roof moves a lot of water
Even in a dry climate, a modest roof sheds a surprising volume of water in one winter storm, and all of it has to go somewhere. Gutters and downspouts exist to collect that water and put it down in a place that does no harm. When they are missing, clogged, undersized or pointed at the wrong spot, the water still comes off the roof. It just lands on wood.
In North County most of the year's rain arrives in a handful of storms, so the damage pattern is a few heavy soakings followed by weeks of drying. Wood survives that if it can dry. Wood that stays wet because a downspout keeps a post base damp for days after each storm does not.
Three ways gutters cause rot
Overflow at the fascia. Leaves and roof grit fill the gutter, water backs up over the rear edge, and it runs down the fascia board the gutter is nailed to. Fascia rot behind a gutter is one of the most common repairs we do, and the gutter hid it until the board was gone.
Downspouts in the wrong place. A downspout that ends at the slab beside a deck post, on top of a deck, or against a stucco wall concentrates all of that roof section's water on one spot. Post bases, ledger ends and door jambs near downspouts rot years before their neighbors.
No gutter at all. Some houses were built without gutters, and some decks and pergolas were added under eaves that never had them. The drip line off the roof edge falls in the same place every storm. Deck boards, pergola beams and fence tops under a drip line show a stripe of gray, checked, soft wood right where the water lands.
How to tell it is the gutter
Look during or right after rain. Water pouring over a gutter edge, a downspout spitting at its seams, or a dark wet stripe on the wall below a gutter end tells the story. Between storms, look for staining on the fascia, streaks on stucco under a gutter, splash marks on siding or posts, and moss or dark staining on deck boards in a straight line parallel to the roof edge.
Then check the gutter itself. Standing water in it means it has lost its pitch. Rust at the back edge means it has been overflowing. A downspout that ends in the air with no extension or splash block is dropping water straight down.
The fixes, in order of effort
Clean the gutters before the rainy season and after the first big wind. Re-pitch any section holding water. Add extensions or splash blocks so downspouts discharge several feet from posts, walls and deck framing, or connect them to a drain line that carries water away. Add a gutter where a roof edge dumps onto a deck, pergola or trim. Install a drip edge behind the gutter so water cannot get behind it onto the fascia.
None of this is carpentry, and all of it is cheaper than the carpentry it prevents. When we repair the fascia or the post that the gutter rotted, we point out exactly what to change so the new wood does not follow the old.
- Clean and re-pitch gutters
- Extend downspouts away from wood and foundations
- Add a gutter over decks, pergolas and exposed trim
- Add drip edge behind the gutter
Grading and codes
Building codes used in California expect the ground to slope away from the foundation and roof water to be carried away from the structure, which is the same idea at the scale of a house. A downspout extension that moves water a few feet is the simplest way to meet it. Where the yard slopes toward the house or the soil stays saturated, a drainage specialist should look at it, because that is a water problem bigger than any piece of trim.
Related questions
Should I add gutters to a house that never had them?
If roof runoff lands on wood, a walkway, or soil against the foundation, yes. If the eaves are deep and the drip line lands on gravel or planting that drains, you may not need them. Look at where the water lands and what it hits.
Do gutter guards stop fascia rot?
They reduce clogging, which reduces overflow, but they do not fix a gutter that has lost its pitch or a missing drip edge. Treat them as a maintenance aid rather than a cure.
Can a downspout drain onto my deck?
It should not. A downspout emptying onto deck boards keeps that area wet, stains the surface and feeds rot in the framing below. Route it past the deck or into a drain line.
Sources and further reading
- California Building Standards Commission (www.dgs.ca.gov)