Is this ok to be left out in freezing temperatures overnight before application?

probably not, and is not recommended in the application specifications either. Read the specification sheet for the product on the amozon site or on the product site. I will say the product was VERY easy too use.

Should I seal up larger cracks before or after applying this?

I would suggest sealing the crack before applying the final top coat of this product. I did that let the sealed crack dry and then did an overall coating with this. Came out great.

How long will this last on my chimney crown? Can you be more specific than just “years”? (Other products say 15 years.)

couldn't tell you, ask me in 15 years.

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Chimney Crown Sealer - Brushable Waterproof Sealant Prevents Leaks - 1/2 Gallon

Product ID: 228360427

Details

Brand
Item Form
Paste
Material
Elastomeric
Style
Compact
Water Resistance Level
Waterproof

💧100% waterproof elastomeric membrane

⏱️Dries to touch in 30-60 mins

🖌️Brush-on, no primer needed

97602CFA

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Sold byAmazon SenegalDelivered byDesertcartCustomer service byDesertcartReturns14 days · 30 with PRO

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Description

🛡️ Seal the deal on leaks before they start—your chimney’s new best defense!

BROAD COVERAGE - Covers up to 20 sq. ft. per ½ gallon, perfect for comprehensive chimney crown protection
QUICK DRY EFFICIENCY - Touch dry in under an hour, fully cured in 2-4 hours—get back to life faster
EFFORTLESS APPLICATION - Brush on two coats directly—no primers or pre-coats required, saving you time
DURABLE WEATHER DEFENSE - Resists chipping and cracking, ensuring long-lasting protection against harsh elements
FLEXIBLE WATERPROOF SHIELD - Elastomeric formula flexes with chimney cracks, preventing leaks for years

MasonryDefender Chimney Crown Sealer is a brushable, elastomeric waterproof sealant designed to protect concrete chimney crowns from water damage. It forms a flexible, durable membrane that resists cracking and chipping, dries quickly within 30-60 minutes, and covers up to 20 sq. ft. per half gallon. Ideal for minor crack repairs, it requires no primer and offers long-lasting leak prevention.

Specifications

ASIN	B08F7ZKG7H
Best Sellers Rank	#25,777 in Tools & Home Improvement ( See Top 100 in Tools & Home Improvement ) #97 in Hardware Sealers
Brand Name	MasonryDefender
Color	Light Gray
Compatible Material	Concrete
Customer Reviews	4.6 4.6 out of 5 stars (560)
Item Form	Paste
Manufacturer	SaverSystems
Material Type	Elastomeric polymer
Number of Items	1
Number of Packs	1
Style Name	Compact
Surface Recommendation	Chimney Crown (Concrete)
UPC	709057000918
Water Resistance Level	Waterproof

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