Clay tile roofs in San Diego's older neighborhoods are often red Mission tile on Spanish Colonial Revival houses, with decorative clay vents and parapets finished in the same tile. A city historic report on a 1926 Mission Hills house describes exactly that, and a 1927 Kensington Manor house in another report has a parapet lined with clay roof tiles. This guide explains how such a roof is kept sound over time.
Key takeaways
- Red clay Mission tile on Spanish Colonial Revival houses is recorded in city historic reports for Mission Hills and Kensington.
- Most clay tile leaks start beneath the tile, at the underlayment, a valley or a vent, rather than in a broken tile.
- Decorative clay vents are small fittings with their own flashing, and they are often where water first enters a tile roof.
- A tile repair is judged on the tile profile, the bed beneath and the flashing, and the look from the street is a secondary test.
- Walk a tile roof only from the ridge and the boards; the tiles break under the wrong weight.
What is on a historic clay tile roof in the city?
A historic clay tile roof is usually red Mission tile laid in courses, with ridge and hip pieces, decorative vents and a parapet finished in clay where the house has one.
The city's Historical Resources Board report on a 1926 Mission Hills house describes a complex roof of red clay Mission tiles with decorative clay tile vents, in the Spanish Colonial Revival style. The same report style covers Spanish Colonial Revival houses across the neighborhood, so the parts described there are the parts a technician expects to find on a similar house.
A roof of this kind is a set of parts, each with its own failure. The field tiles shed the water, the ridge and hip pieces seal the top, the vents carry the air out, and the underlayment beneath carries whatever gets past the tile. Care means keeping each part in its place rather than replacing the whole roof at the first crack.
Why do clay tiles crack, and which cracks matter?
Clay tile cracks where a load lands on it at the wrong point or where movement in the frame pushes a tile out of line. A hairline crack in a tile that still lies flat and overlaps its neighbor is often left alone.
Clay is strong in compression and weak across a single point. A tile set on a batten with a gap, or one stepped on by a worker in the wrong place, can split along a line that does not show until the next rain. Frame movement can also rock a tile until its nib breaks.
The test is simple and it is applied on each visit. Does the tile still lie flat? Does it still overlap the one below? Does it still shed water into the channel beneath? If all three are yes, the tile can usually stay, and the record notes the crack so that a later check can see whether it has grown.
- A tile that has slipped so its lower edge sits proud of the course below is replaced
- A cracked tile that lets water through is replaced at once
- A hairline crack in a sound, flat tile is noted and watched
- A tile that rocks on its nib is re-set or replaced
How are the underlayment and the bed checked?
The underlayment is the water-shedding layer beneath the tile, and on an old roof it is often the part that has failed. It is checked where tiles are lifted, at the valleys, around the vents and along the eaves.
An old felt or paper underlayment dries, cracks and tears at nail holes. Once it has lost its flexibility, a tile repair that does not address it will leak again within a season. The technician records the condition of the layer where it can be seen and says plainly when a larger section needs to come up.
The mortar bed beneath ridge and hip pieces is the other check. Old mortar turns to sand and lets the pieces rock. The bed is cut out and renewed where it has failed, and the new bed is laid to fall outward so water leaves the roof rather than sitting on the joint.
How should decorative vents be looked after?
A decorative clay vent is a small fitting with a cap, a seat and a flashing under it. It is often where water first enters a tile roof, so it is checked on every visit, from the roof and from the attic beneath.
The seat is flashed into the roof, and the cap is set to shed rain. Both can loosen over time and let water run down the vent body into the framing below. A stain on the boards beneath the vent, or a soft patch on a rafter, shows where the water has been.
A vent repair re-makes the flashing, re-sets the cap and dries the attic boards before the room below is closed. Where a vent has been covered over during an earlier re-roof, it is reopened so the attic can breathe.
| Part | What to look for | What to do |
|---|---|---|
| Field tiles | Cracks, slips and tiles that rock | Replace the broken tile; re-set the slipped one |
| Ridge and hip | Movement, cracked mortar and open joints | Re-bed the piece and seal the joint |
| Decorative vents | Loose caps, lifted seats and stains beneath | Re-make the flashing and re-set the cap |
| Underlayment | Torn or brittle felt seen where tiles are lifted | Replace the affected area in the same course |
| Valleys | Dark staining and nail holes in the metal or felt | Clear, re-line and test with water |
How is the heritage look kept on a repair?
The look is kept by salvaging sound tile from a part of the roof that is not seen, matching the profile as closely as the stock allows and testing a match on a discreet slope first.
Salvaged tiles are the first choice for a repair on a historic roof, since they carry the same color and the same wear. A rear slope or an outbuilding is the usual source. Where salvage is not enough, a tile of the nearest profile is set on a discreet slope first, so the owner can see the match before the main repair goes ahead.
The owner is told plainly what matches and what does not. A visible mismatch is not a leak, and it does not always justify a full re-tile. The decision is written on the scope with the reasons, so the owner can weigh the look against the cost of the alternative.
What does a clay tile roof need after a heavy storm?
After a heavy storm, a clay tile roof is checked from the ground for slipped courses and displaced ridge pieces, and from the attic for water on the underlayment and the boards. Debris is cleared from the valleys and the gutters before the next rain.
Wind-driven rain pushes water under tiles that have lifted, and a branch or a flying object can crack a tile in a single blow. The ground check looks for a new gap in a course, a ridge piece that has moved and a tile that lies at an unusual angle. Each is photographed from the same spot as before.
The attic check follows the same path as a leak trace. Wet underlayment, staining on the boards beneath a valley and dark marks on the rafters near a vent all point to water that has entered. Where the water has come through, a technician dries the framing and traces the entry point before the tile is repaired.
Debris is cleared from the valleys and the gutter outlets as a routine after any storm. Leaves and grit held in a valley hold water against the tile, and the weight of wet debris can lift the course above it.
How is a historic tile roof recorded for the next visit?
A record of each visit names the parts checked, the tiles counted, the repairs made and the photographs taken. The record makes the next visit faster and lets a later owner see what was done.
The count of tiles replaced is recorded by course, so a later technician can see whether one area of the roof is failing faster than the rest. A cluster of replacements on one slope points to a cause, such as a branch rubbing the surface or a fixing that has worked loose.
The photographs are taken from the ground, from the ridge and from the attic, with the date and the room or slope named. A set of photographs from one year to the next shows the change in the tile and the bed more clearly than any written note.
When does a tile roof need more than repair?
A tile roof needs more than repair when the underlayment is failing across many slopes, when the battens have rotted or when too many tiles have slipped for the course to hold. At that point a re-tile, with the underlayment renewed, is the sounder choice.
A tile repair is limited by what it can reach. If the felt beneath has failed across several slopes, each repaired tile sits on a layer that will leak, and the repairs multiply without solving the fault. A technician records the extent of the failed layer and says when a re-tile is the better choice.
Battens that have rotted under the tile cannot hold the tile reliably. The check is made from the attic, where the battens are visible, and from the ground where a course has dropped. A full re-tile is scoped with the battens renewed, the underlayment replaced and the salvaged tile re-used where it is sound.
The owner is told the reasons on the scope. A re-tile is a larger decision than a repair, and the owner should have the facts from the record before choosing.
Frequently asked questions
Can a clay tile roof be walked on for an inspection?
Only on the boards and at the ridge, and only by a technician. The tiles break under a person's weight, and a fall from a tile roof is serious.
How often should a tile roof be checked?
A check once a year from the ground and from the attic is a practical rhythm, and after any storm or branch fall. Call (833) 751-2102 for a visit when a fault is seen.
Will a repair change the look of the house?
A close match is the usual result. Salvaged tiles are used first, and the technician tells you where a new tile will show before the work starts.
Sources
- City of San Diego Historical Resources Board report on a 1926 Mission Hills house
- City of San Diego historic report on a 1927 Kensington Manor house
This guide is general information for San Diego County homeowners, not a substitute for an on-site inspection. Prices are estimates. See our disclaimer.