I used four layers of aluminum foil that I superglued to the chimney
crown plus I primed and oil-base pained (red) whole chimney. Working
so far - second day of downpours and it ain't leakin' no drop into
When I had the top of my chimney done I used Sure Klean masonry
sealer. I put it on after about a month of allowing the concrete to
cure and a week of dry weather. I think this stuff was about $35 a gal
but I was told its one of the best you can get. I couldnt find it in
any size smaller than a gallon.
A "Stock" mixture of 1 lb Sodium Hydroxide (Lye) and 5 lbs of
Hydrated Aluminum Potassium Sulphate (common ALUM) mixed with 2
gallons of pure water.
One PINT of this mixture is added to 10 lbs of either common or
portland cement and thinned to brushing consistancy with water. This
is brushed onto fresh concrete (within 3 to 4 days) with a whitewash
brush. It will foam when applied, and forms an "impervious" finish on
the concrete making it resistant to damage from salts etc and prevents
water from migrating through the concrete.
You could likely scale down the batch size of both the "stock mixture"
and the final mix.
The Sure Klean was bought at a contractors specialty supply house, not
found at HD or the othere place. Im sure google can supply this info.
Ive heard of people using aluminum paint to seal concrete, never tried
it though. Ive heard a lot of claims to this effect over the years but
never seen it tested.
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