Self-leveling lap sealant goes on flat, horizontal seams and around roof vents, pipes and screw heads. Non-sag sealant holds its bead on sloped and vertical faces such as termination rails and tall flanges. Either way, use a sealant the maker lists for your roof: a rubber (EPDM) or thermoplastic (TPO) membrane, or fiberglass.
RV Roof Sealants: Self-Leveling vs Non-Sag, and What Fits Your Roof
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At a glance
- Flat seams: self-leveling lap sealant around vents, vent pipes and screw heads.
- Vertical faces: non-sag sealant on termination rails, tall flanges and sidewall joints.
- How often: builders call for a sealant check every 90 days to every six months, and a reseal once a year.
On this page (6)
Our picks
- Dicor 501LSW self-leveling lap sealant, white: horizontal seams, vents, vent pipes and screw heads on EPDM, TPO and PVC
- Dicor 551LSD non-leveling lap sealant, dove white: for termination rails, roof edges and taller flanges
- Dicor 651SANSW non-leveling Ultra Sealant, white: joints around rooftop accessories; on TPO and EPDM Dicor pairs it with its Ultra Sealant Primer
- EternaBond RoofSeal tape, white, 4 in x 50 ft: covers a seam on EPDM, TPO and fiberglass; apply between 40 and 150°F
Self-leveling or non-sag?
Pick by the angle of the surface. Self-leveling sealant flows out and settles flat, so it belongs on horizontal joints. Non-sag sealant stays where you put it, which a vertical or slanted face needs. Alpha Systems draws the same line in its repair procedure.
Roof edges can take either. Dicor lists edges for both its 501 self-leveling lap sealant and its 551 non-leveling version, and suggests the 551 mainly for taller flanges such as TV antennas. Follow the wording on the product you are holding.
| Sealant | Where it goes | Roof types the maker lists |
|---|---|---|
| Dicor 501 self-leveling lap sealant | Horizontal seams, roof edges, air vents, vent pipes, screw heads | EPDM, TPO, PVC |
| Dicor 551 non-leveling lap sealant | Roof edges, termination rails, taller flanges | EPDM, TPO, PVC |
| Dicor Ultra Sealant, self-leveling or non-leveling | Voids and joints around rooftop accessories; roof perimeter | TPO and EPDM, but only with Dicor Ultra Sealant Primer |
| Geocel ADVANCED SL EPDM | Horizontal only: roof edges, vents, screw heads | White EPDM. Not TPO, not black EPDM, not vertical surfaces |
| Geocel ADVANCED RV EPDM Roof Sealant | General EPDM roof repair | White EPDM, primed TPO, primed PVC |
| Geocel Pro Flex RV | Vents, trim, moldings, seams, tail lights | Not for use on EPDM |
| Alpha 1021 self-leveling | Flat horizontal surfaces, around skylights and fixtures | Rubber, metal and fiberglass roofs |
| Alpha 1010 non-sag | Slanted, uneven and vertical surfaces, sidewalls, end rails | Not named on Alpha's data sheet |
| Sikaflex-715, semi self-leveling | RV roof components; Sika says experienced professional users only | EPDM and metals |
From the makers' product data sheets: Dicor, Geocel, Alpha Systems and Sika.
Tip: Makers disagree about TPO, as the table shows, and Alpha Systems allows only SuperFlex brand sealants on its SuperFlex membrane. When the roof maker and the tube disagree, go with the roof maker.
Know your roof: EPDM, TPO or fiberglass
Check which roof you have before you buy, because the sealant has to match it. EPDM and TPO are flexible membranes glued to plywood or OSB decking. Fiberglass is a hard molded panel, and Dicor's fiberglass roof coating is not recommended for EPDM rubber or TPO. Your builder's manual or dealer can confirm which you have.
Keep two things off any membrane. Silicone is one: Keystone bans it on the roof, and Dicor says it will not adhere to its membrane. The other is cleaners with petroleum distillates, which Alpha and Dicor both say damage the membrane. Alpha rules out acetone too.
How often to inspect and reseal
Most builders want an inspection every three to six months and a reseal once a year. Check the slide-out seals and all four sides on the same walk around.
- Keystone: inspect the roof at least every 90 days, other sealed exterior areas every six months.
- Winnebago Towables: inspect every 3 months, reseal at least once a year.
- Jayco: inspect all sealants at least every six months, reseal at least once a year.
- Grand Design: every three months in the Imagine manual.
- Forest River: inspect roof components at least twice a year.
- Alpha Systems: at least quarterly inspections, documented in writing, under the AlphaPly warranty.
Look for cracks, shrinkage, gaps, peeling and lifting. Heavy sun, big temperature swings and cold climates speed this up, so a roof in Arizona may need attention sooner than one in Ohio. Fold these checks into your exterior care routine.
Tip: These intervals are warranty terms. Forest River may treat unmaintained seals as abusive treatment, Grand Design's Reflection warranty asks for documented sealant inspections, and Alpha's warranty is void if any membrane component is not an Alpha product. Keep receipts and dated notes.
Resealing, step by step
Most of a reseal is getting the old joint clean; the new bead goes on with an ordinary caulking gun.
- Check that your roof is rated to walk on; ask a dealer or service tech if unsure.
- Pull up loose, cracked sealant by hand. Alpha and Grand Design both say to use no putty knife or other sharp tool that could puncture the membrane. Sealant that will not come off by hand still has good adhesion: leave it.
- Clean with a non-abrasive household cleaner and water, not solvents, and let it dry completely.
- Lay a 1/4 to 3/8 inch bead. Dicor's retrofit guide puts it at appliances, both ends of the termination molding, the top edge of the side roof edge molding and over every roof screw head.
- Watch the temperature. Alpha lists an application range of 5 to 120°F (minus 15 to 49°C). Geocel's self-leveling EPDM sealant says not below 30°F, and Dicor's Ultra Sealant above 40°F. In cold weather, warm the tube at room temperature first.
Whether new sealant may go over old depends on who made your roof. Alpha says to apply its correct sealant generously over existing sealant. Keystone warns against layering two different sealants, because water can slip between them: match the original or strip it all.
Plan around cure time. Dicor's lap sealant at 50 to 70°F is waterproof in 4 hours and fully cured in 30 days. Alpha's sealants generally cure fully within 48 hours. Bubbling or slight lifting under fresh Dicor 501 is normal and settles within about two weeks, and sealant should go on roughly 2 weeks before any roof coating.
Seam tapes and roof coatings
Tape covers a seam instead of filling it, and a coating protects a sound roof but does not fix one. EternaBond tape bonds to EPDM, TPO and fiberglass between 40°F (4°C) and 150°F; remove old cracked sealant first and roll it down with a steel roller. Alpha says its recoat system is only for membranes that are not leaking. If water is already getting in, start with finding and patching the leak.
Common questions
How often should I reseal my RV roof?
There is no fixed replacement date. Dicor says its lap sealant's life span depends on region and conditions, so repair or replace it as your inspections show wear. Alpha folds the sealant check into its recommended cleaning, three to four times a year.
Can I use Flex Seal on an RV roof?
Flex Seal says to test a small area first, and it lists EPDM for Flex Paste. No roof maker or builder document reviewed here names it, and Alpha and Dicor tie their roof warranties to approved sealants, so it can put that coverage at risk.
What goes wrong with RV roof sealant?
It loses flexibility and pulls away from the joint. Jayco notes that sealants have no set lifetime, because weather decides how long they stay pliable and stuck.
Do I need to remove the old sealant before resealing?
Not always, but some makers insist on it. Sika says removing existing products is crucial for repairs to avoid compatibility issues, and Sikaflex-715 cannot be painted over.