The decision depends on a variety of factors: the type of roof you have, what is causing your leaks or issues, and how long you need this repair to last.
The best use of roof sealant is for small, localised problems: a split at a joint; a failed detail around the base or collar of one pipe vent penetrating your shingles, for example. While it is fast and low-priced, roof coating does nothing to cure extensive wear, moisture entrapment, or active movement in the wood framing.
Use sealant where: The point of leakage can be identified, if the substrate is in good condition and for a small area. For Roof sealant, consider https://www.ct1.com/product-applications/ct1-the-ultimate-roof-sealant
With roof coating (usually liquid-applied), it is a system, not just one spot or area that is repaired. It is applied across a larger area to provide continuous waterproofing, enhance UV resistance and increase the lifespan of an ageing roof. The moral of the story is, preparation is everything – if a roof is moist, dirty or delaminated from damage (a common situation with older roofs), a coating simply will not bond properly and fail quickly.
Coating is for a good condition but weathered roof, and you want a longer-term upgrade without removing the entire old roof.
Re-roof – Generally, if the roof isn’t suitable anymore – for example, cracking all over, breaking everywhere or leaks appearing in a repetitive pattern on different sections. Perhaps it even has wet insulation trapped beneath ponding water due to insufficient falls and/or structural faults. This is the more expensive option, but it actually cures instead of simply treating symptoms.
