Los Gatos and Saratoga sit in the Santa Cruz Mountain foothills south-west of San Jose, and Redwood Estates is an unincorporated redwood-forest community in the same hills. Roofs in these places sit under trees and on steep slopes, and the trees, the shade and the slope together wear a covering faster than an open roof on the valley floor. This guide explains how those roofs are kept sound.
Key takeaways
- Branches that rub the covering wear the granules at one spot, and a limb that rests on the roof can crack a tile or lift a shingle.
- Leaves and needles block gutters and collect in valleys, holding water against the covering and the sheathing.
- Shade keeps the north faces wet, and moss and staining grow there first.
- Tree work belongs to a qualified arborist; the roof crew records the contact points and does not cut trees.
- A clear routine of gutter cleaning and valley checks prevents most of the overflows that trees cause.
How does a tree wear a roof?
A tree wears a roof by rubbing, dropping debris and holding moisture. Each works in its own way, and each shows in a different place on the covering.
A branch that moves in the wind rubs the covering at the point of contact. The granules come away, the mat beneath is exposed and the covering begins to fail at that spot. Because the damage grows slowly, it is often found late, after a storm has found the weakened area.
A limb that rests on the roof can crack a tile, lift a shingle at its edge or dent a metal panel. The contact point is recorded so the arborist and the owner have the same map of the problem.
Why do the gutters and valleys fill?
Leaves and needles collect in the gutters and the valleys and form a wet mat. The mat holds water against the covering and the sheathing, and the wet can persist for days after the rain.
The debris also adds weight at the eave. A gutter that is holding a mat of wet leaves sags, and the sagging run holds a pool at its low point. The pool overflows at the first heavy rain and runs onto the fascia.
A valley full of debris is worse, because it carries the flow from two slopes and forces the water into any nail hole or lap. The technician clears each valley by hand and tests it with water.
- Clear the gutters after each big leaf fall and before the wet season
- Clear each valley by hand, not with a high-pressure jet
- Test each run with water and note where it holds a pool
- Check each outlet for a clean discharge away from the wall
What does shade do to the covering?
Shade keeps the roof wet for longer after rain. Moss and dark staining grow on the north and shaded faces first, and the wet softens the sheathing and loosens the nails beneath.
Moss holds the moisture against the granules and the mat. Over time the wet works into the nail holes and the edges of the covering, and the damage then spreads across the shaded face.
Moss is cleaned gently with a soft brush and a low-pressure rinse. A hard brush or a strong jet strips the granules, and the covering is then less able to shed water. The sheathing beneath the worst areas is checked from the attic for softness.
Who should deal with the trees?
Trees that touch or overhang the roof should be assessed by a qualified arborist, who decides what to cut and how. The roof crew records the contact points and does not cut trees, since a limb cut from a ladder is a serious fall risk.
The owner asks the arborist to assess the canopy over the roof and to cut back any limb that touches or is likely to fall onto it in a storm. The arborist's assessment is kept with the roof file, so the work is planned in order.
The roof crew's job is the covering, the gutters, the valleys and the attic. Keeping the tree work separate keeps each job with the people equipped for it.
What is the routine for a wooded foothill roof?
A routine has three parts: a clean and a flow test of the gutters and valleys after each leaf fall, a check of the covering and the shaded faces before the wet season, and an attic check after the first storm.
The gutters are cleared after each big leaf fall and tested with water. The valleys are cleared by hand and the outlets are checked for a clean discharge.
Before the wet season, the covering is checked from the ground and the ladder, the shaded faces are looked at for moss and staining, and the attic is read for dark sheathing. The record is kept with photographs from the same spots.
How does a steep foothill slope change the flow?
A steep roof sheds water quickly, and the flow from the top of the slope arrives at the eave with force. The gutter and the outlet at the eave must carry that flow, and the valleys and penetrations on the slope see it at full strength.
On a steep slope the water does not spread out across the covering; it runs in a few narrow lines toward the valleys and the gutter. Each line finds the nearest gap, so the valleys, the vent flashings and the chimney flashing near the middle of the slope take the most water.
The technician therefore reads the slope from the top down. The ridge, the upper valleys and the first penetrations are checked for the flow they carry, and the outlet at the eave is sized and placed for the total that reaches it.
What does a foothill owner need from the ladder and the access?
A foothill roof needs a ladder set on firm ground, tied off at the top and kept inside its rails, and fall protection for any work on the slope. The access is planned before the first visit.
The ground under a foothill house is often sloping and may be soft after rain. The ladder is set on a level pad or a board, and the crew checks the footing before it climbs. A ladder that moves on a wet slope is a serious hazard.
The crew avoids the wet covering and works in the dry hours. The work is paused in a gust that could move a loose piece or the ladder, and the open area is covered before the crew leaves for the day.
How is a repair recorded on a wooded lot?
A repair on a wooded lot is recorded with the contact points of the trees, the debris cleared from each valley and gutter, the moss treated and the covering or flashing repaired. The record is what the next visit starts from.
The record names each contact point on the plan of the roof, with the branch's position noted, so the arborist and the owner can see the problem in the same place. The debris cleared is recorded by the valley or the run it came from.
The photographs are taken from the same spots each season. A change in the moss, the granules or the debris is then easy to see, and the routine is adjusted to what the record shows.
What do the foothill towns' long slopes mean for the eave gutter?
The eave gutter on a long foothill slope carries the whole flow of the roof, and it is the part most likely to overflow in a storm. Its size, its fall and the number of outlets decide whether it keeps up.
A gutter of the usual size on a long slope is at the limit of its capacity in a heavy storm. The technician measures the roof area draining to the run and the number of outlets, and adds an outlet where the run is too long for the flow.
The fall of the run is tested with water from the far end. A run that holds a pool at a dip overflows at that point, and the dip is corrected before the outlets are checked.
Why is the fascia behind the foothill gutter checked?
The fascia behind a foothill gutter takes the overflow from any dip or blocked outlet, and it softens quickly in the damp under the trees. The fascia and the rafter tails are probed on each visit.
Soft fascia shows as a paint blister, a dark stain along the lower edge or a board that gives under a screwdriver. The technician replaces the soft section and re-fixes the gutter into solid backing before the run is re-tested.
The rafter tails behind the fascia are checked from the attic where possible. A tail that has softened is cut back and sistered, so the gutter has a firm base again.
How is the canopy reassessed after a tree is cut back?
After an arborist has cut back a limb, the roof is checked again. The new light and the new exposure change where the moisture sits, and the routine is adjusted to the change.
A limb removed from over the roof lets sun reach a face that was shaded, and the moss on that face begins to dry. The shaded faces are re-read on the next visit, since their needs have changed.
The owner keeps the arborist's note with the roof file. The two records together show what was cut, why, and how the roof has responded in the seasons since.
What does a foothill owner tell the next buyer?
A foothill owner keeps the routine and the record together so a buyer can see how the roof has been kept under its trees. The record is more persuasive than any general statement about the roof's condition.
The buyer or the buyer's inspector reads the list of clearings, the dated photographs of the shaded faces and the notes of each repair. Those show the roof's history under the canopy and the care it has received.
A record that shows a fault found and fixed is a better sign than a clean-looking roof with no history. The owner keeps the file in a place where it can be found and shared when the house is sold.
Frequently asked questions
Will the crew trim the trees over the roof?
No. Tree work is for a qualified arborist. The crew records the contact points and recommends the work to the owner.
Is moss a sign of a leak?
Not by itself, but it shows the roof stays wet, and the wet can soften the sheathing. The technician checks the boards beneath the moss.
How often should the gutters be cleaned on a wooded lot?
After each big leaf fall and before the wet season is a practical rhythm. The technician sets the routine on the scope.
Sources
This guide is general information for Santa Clara County homeowners, not a substitute for an on-site inspection. Prices are estimates. See our disclaimer.