I have some mold in patches on the outside of my house. It is wood
hardboard siding; house is about 24 years old. I'm about to re-paint.
My question is, do I paint 100% with Kilz or can I just do Kilz over the
mold and regular paint everywhere else. The Kilz is more expensive. Thanks
for any advice.
If you get rid of the mold that is there today and whatever caused it, there
is no reason to use Kilz in the first place.
1) Spray the whole house with a water/bleach solution then rinse the house
to get rid of most/all of the existing mold.
2) Identify the root cause of the mold and eliminiate it if possible...
(Leaky gutters, insufficient circulation behind shrubs, etc).
3) Prime and paint with whatever materials you want.
Kilz is to block stains from transferring through to the finish coat. It is
very useful if you have water damage or mildew stains on interior surfaces,
but on exteriors, you should be able to eliminate the mold and stain before
you prime/paint, so kilz isn't necessary.
If you see mold then spray the entire area area with bleach and wash,
there will be contaminents you cant see growing yet. Kills is not the
best product but primer is only needed if surface is bare or poor.
Having a clean non glossy surface is the big concern. Bleach and
powerwash with handscrubbing bad areas is usualy enough. But never paint
over mold or dirt. If surface is gloss go to a real paint store Sherwin
williams has paints that adhere to gloss or powder. Your cheap HD stuff
will fail on difficult surfaces. You local pro store is best to answer
your specific issues. Sherwin Williams usualy can get out to see it if
you buy from them. Its the little things you do that make a 2 yr or 30
Sherwin williams guarntees a paint for life, I guess that means 1 owner.
20 yr has been out for 15 years. On new wood oil primer 2 coat sure, it
may look like crap in 10 and be faded but bonding is the issue. On a
repaint the new coat is only as good as what it is put over, then you
cant know how long anything will last even if your job is perfect. Paint
is better then ever in how it lasts, but failure is often not the paints
fault, its moisture, poor prep, a hot surface when painted.
In my opinion SW is a mediocre paint. It does not adhere well. You can see
the problem during clean up. It is very easy to clean brushes, etc. On the
other hand Benjamin Moore is a pain to clean up brushes and adheres very
There are loads of good sealer/primers matched with good paint brands.
Kilz' claim to fame is stain hiding power, especially for "oily" woods
that tend to bleed through paint.
My intro to Kilz was in covering a stain, from coca cola that got
splattered on kitchen ceiling. It was washed, of course, but the paint
I put over it stained much more where the coke had not splattered.
Wierd. No paint job will be better than the prep, and you still must
assure the surface is clean.
If you have an exterior that has areas where mold is a problem, getting
max sun exposure helps (clear shrubs that are up against the siding,
etc.) Semi-gloss may be a better choice than flat, as mold can't hang
on quite as easily. Choose a good brand of paint at a paint store, read
up on the tech specs on the website. Make sure the area is dry, not too
hot or too cold, chalk removed, loose paint scraped off, etc. All that
fine print on the label is there for a reason. Pay attention to times
for recoating, etc. Don't prime this year and paint next year.
There is no paint or primer that I know of that is to be painted over
mold, mildew, chalky paint, grease, dirt, etc. Mildew should be cleaned
with about 10% bleach. Don't know the proper way to prepare chalky
paint on wood - on concrete block/stucco, it is to pressure wash after
the bleach treatment.
Last time I checked a Kilz label, it carried a warning about mold/mildew.
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