Roof Repair and Replacement, in detail

The first thing measured on a roof job is what the roof actually is, because the three materials fail differently and take different repairs. EPDM is the rubber membrane most owners mean when they say rubber roof. It chalks white, it stays flexible for years, and it is bonded to decking with a contact adhesive. TPO is a thermoplastic, usually brighter white, which does not chalk and can be heat welded rather than glued.

One piece fiberglass is a different animal. It is a moulded laminate rather than a sheet, it is often walkable without decking underneath doing all the work, and it cannot be patched with tape and a prayer. Owners who have owned both are usually surprised that a fiberglass roof is the harder repair, not the easier one, because a crack in a laminate is a structural defect rather than a hole in a skin.

A fiberglass roof cracks where it is stressed, which means at the front cap transition, around an air conditioner opening, and along the line where a ladder or a rack foot loads it. The crack is rarely the whole story. Water tracks into the laminate through it and delaminates the gelcoat from the substrate for some distance in every direction, so the sound area is always larger than the visible line by the time we get to it.

Diagnosis here is acoustic and physical. We sound the panel with a plastic tap hammer and listen for the dull note that means the laminate has separated, marking the boundary in tape as we go. That boundary, not the crack, defines the repair area. On a coach where the roof also carries an air conditioner, the unit comes off first so the flange bed can be inspected, because a crack that starts at an AC opening corner is the single most common pattern we see.

The repair itself is grind, bevel, layup and fair. Damaged laminate is ground out to a feathered bevel, new glass is laid in with resin to restore the original thickness, then the surface is filled, blocked and refinished. Structural work bills at the posted body and paint rate of $210 per hour and body supplies calculate at $5 per body hour. On a coach with a coloured roof or a graphics wrap that runs up over the edge, refinish hours add meaningfully to the total.

• Tap sounding to map delamination beyond the visible crack, boundary marked in tape
• Air conditioner removal where the crack originates at the opening corner
• Grind to a feathered bevel, no vertical edges left in the laminate
• Layup restored to original laminate thickness, not filled with body filler
• Gelcoat or refinish to match, blended rather than edged at the repair line

Every roof estimate here starts with a count, not a look. A roof is a list of holes with a sheet over them, and each hole has a flange, a bed of sealant under that flange, and a bead of lap sealant over the fasteners. Quoting a reseal without counting them is how a shop lands on a number it then has to supplement, which is exactly the surprise at week three that nobody wants.

The count also tells you where the money is going. A short travel trailer roof with a single vent, one fan and no air conditioner is a genuinely small job. A forty foot diesel pusher with two air conditioners, three vents, a bathroom skylight, a satellite dome, a Winegard antenna, a refrigerator vent and two cap seams is a different quote entirely, and the membrane area barely changed between them.

• Air conditioner flanges and the gasket bed under each shroud
• Vent and fan flanges, Fan-Tastic and MaxxAir among them
• Refrigerator roof vent, which leaks into a cabinet and gets found late
• Antenna base, satellite dome and any solar panel mounting foot
• Front and rear cap seams plus both sidewall termination bars

Decking condition is the hinge the whole price swings on. A roof that has leaked at one flange for a season usually has a localised soft area of luan or plywood around it, which is a defined replacement of a few square feet. A roof that has leaked at a cap seam for three years has water that ran down the length of a rafter bay, and the soft area is a strip rather than a spot.

We probe before teardown where we can, pressing along the roof from above and looking for deflection between rafters, and we tell owners honestly that this is an indication rather than a measurement. The real number arrives when the membrane comes off. That is why a roof estimate is written as a range with a stated teardown point, and why a supplement on this kind of work is normal rather than a sign something went wrong.

Not every RV roof is rated to carry a person. A walkable roof has decking and rafter spacing designed for it. A non walkable roof, common on lighter travel trailers and some fifth wheels, does not, and the damage from someone standing between rafters is a compressed decking panel with a stretched membrane over it that will crack at the low point within a year.

We see this most often after an owner has been up there resealing, which is worth saying plainly because the six month sealant inspection we recommend has to be done from a ladder or on kneeling boards if the roof is not rated. Walking a non walkable roof to save the cost of a reseal is a reliable way to buy a membrane replacement instead.

Dicor self levelling lap sealant is for horizontal surfaces and flange perimeters, where it flows out and self seals against the flange edge. Non levelling sealant is for vertical surfaces, including the termination bar and the sides of a raised flange, where a self levelling product would simply run. Using the levelling product on a vertical seam is a common owner error that looks fine wet and sags into a ridge as it cures.

Eternabond tape is a different tool with a different job. It belongs on a long straight seam, applied to a properly cleaned and primed surface, rolled hard with a steel roller so there is no air path under it. Tape over an existing cracked sealant bead traps water rather than excluding it, and once tape has been laid over a bad bead the eventual repair is more expensive because the tape has to come off before anything else happens.

Twenty hours is a reseal on a short roof with a modest penetration count, done properly with old sealant removed rather than buried. Eighty hours is a long coach stripped to bare decking, with rot replaced, two air conditioners out and back in, a new membrane bonded and rolled, every flange rebedded, and a refinish where the roof edge is visible.

Calendar time runs longer than labour on all of it, for the reason cure has no shortcut. Adhesive needs its time, self levelling sealant needs to level and skin, and a water test after that is not meaningful until the sealant has actually set. Plan on a working week for a reseal and on the better part of two for a full replacement, plus whatever the parts wait adds on top.