Roof sealants are useful, but they are not a cure-all. The right product depends on what is leaking: a cracked tile, a flashing joint, a ridge cap or a pipe through the roof. Some jobs call for a sealant as the permanent fix; others need the tile, flashing or pointing replaced, with sealant only buying time until then.
The short answer
- Match the sealant to the surface and the job
- Cracked tiles should be replaced, not sealed
- Flashing edges and penetrations suit sealants and tapes
- Ridge caps need flexible pointing
- Wet-weather compounds help in an emergency
Which product for which job
| Problem | Better fix | Products |
|---|---|---|
| Cracked or broken tile | Replace the tile | Matching roof tiles |
| Cracked ridge or hip pointing | Repoint | IRC Point Protect, RGL Supa Point |
| Leaking flashing edge or joint | Reseal or replace flashing | Silicone, flashing tape, flexible flashing |
| Pipe or vent penetration | Seal around the penetration | Flash Protect, Rapid Flash, silicone |
| Leak during rain | Emergency seal, then proper repair | Fastfix Wet Shield |
Temporary vs permanent fixes
Sealant on a cracked tile can stop a drip, but the crack keeps moving and the sealant eventually lets go. Tiles are cheap compared to water damage, so replace them. Our tile buying guide shows how to find a match.
On flashings and penetrations, a quality sealant or self-adhesive flashing tape can be a lasting repair, provided the surface is sound and clean. Ridge caps are different again: they need flexible pointing, which is made to seal and fix ridge caps and move with the roof.
Flashings and penetrations
Flashing joints are where most lasting sealant work happens. Common jobs include the top edge of wall flashing, laps between flashing lengths, and the collar around pipes, vents and solar mounts.
- Silicone: good for sealing the top edge of flashing to a wall and small gaps. Use a roofing-grade product and a proper silicone gun.
- Self-adhesive flashing tape: Flash Protect and Rapid Flash bridge joints and seal around penetrations, and stay flexible.
- Flexible flashing: where old flashing has split or corroded, replace it with lead-free flexible flashing such as Fast-a-Flex or Dakaflash. See our flashing guide.
- Waterproofing membrane: IRC Point Protect Flexi is a flexible membrane for joints and flashings as well as ridge caps.
A roof repair kit to keep in the shed
- Fastfix Wet Shield for emergency leaks
- A silicone gun and roofing silicone
- A roll of self-adhesive flashing tape
- A few spare tiles that match your roof
- A tub of flexible pointing in your ridge colour
Having these on hand turns a storm-night leak into a quick fix and a planned repair, rather than an emergency call-out. Keep spare tiles from the original roof where you can; they are the best colour match you will find.
Sealing in wet weather
Most sealants need a dry surface. Fastfix Wet Shield is a resin-based, fibre-reinforced roof repair compound made to waterproof immediately, even in wet conditions, on tile, metal, concrete, brickwork, gutters, valleys and flashing. It is the product to keep on hand for leaks that cannot wait.
Do not go on a wet roof. For storm damage that needs emergency help in Victoria, contact VICSES on 132 500.
Applying sealant properly
Walking on tiles cracks them and puts you at risk of a fall. WorkSafe Victoria treats falls from roofs as a serious hazard and puts edge protection ahead of ladders and harnesses. If you are not trained and equipped to work at height, use this guide to buy the right products and brief a roofer.
- Find the real source. Water travels along timbers, so the stain inside is often not under the leak.
- Clean dirt, moss, old sealant and loose material from the area.
- Dry the surface, unless the product is designed for wet application.
- Apply a continuous bead or patch, working it into the joint.
- Tool it smooth so water runs off rather than pooling.
- Check after the next rain and plan a permanent repair where needed.
We stock silicone guns, silicones, Wet Shield, flexible pointing and self-adhesive flashing at our Doveton and Mulgrave yards. See roofing materials.
If the leak is hard to find or the roof is unsafe to walk on, our sister business Royce Roofing repairs roof leaks across Melbourne.
Common questions
What is the best sealant for a leaking roof?
It depends on the leak. Flashing joints and penetrations suit silicone or flashing tape; ridge caps need flexible pointing; wet-weather leaks suit a product like Fastfix Wet Shield.
Can I seal a cracked roof tile?
As a short-term fix only. The lasting repair is replacing the tile with a matching one.
Can you apply roof sealant in the rain?
Most sealants need a dry surface. Fastfix Wet Shield is made to waterproof immediately, even in wet conditions.
Is silicone OK on roof tiles?
Silicone suits flashing edges and penetrations. It is not a substitute for replacing cracked tiles or repointing ridge caps.
How do I find where my roof is leaking?
Water travels along timbers, so start above the stain and work uphill, checking flashings, valleys, penetrations and ridge caps.
Related
Sources: VICSES; WorkSafe Victoria: Prevention of falls in housing construction.
