Moisture Makes Paint Peel
The moisture damage to this patio ceiling could have been created from a
variety of other problems. However, the most common problem you're going to
have in a situation like this underneath an exterior patio cover will
usually have something to do with the roofing or roof covering.
The
first thing I would check would be the roof shingles, make sure the roof is
in good shape and isn't damaged or missing shingles.
The paint could
also be peeling, because the surface wasn't cleaned properly before the next
layer of paint was applied. Some exterior and interior walls and ceilings
will get dirty and sometimes even develop some type of oily film and if this
layer of grime isn't removed, then there's a good chance the paint won't
stick and end up peeling off like this.
Paint can also peel and flake
off, when it's overly thinned out. For example if you have one gallon of
water based paint and mix it with 1 gallon of water, it might not stick as
well to the next surface you're planning on applying to.
I've also
seen paint do this when applied to wood with high levels of moisture. For
example, one time I painted a wet 2 x 4 that was recently purchased from the
lumberyard and within a few months, the paint started flaking off.
If
you're planning on painting any wood, make sure it's dry and process used
for this is usually referred to as kiln dried. This is when they dry large
amounts of lumber inside of heated or well ventilated tents or buildings.
Again, there could be a variety of reasons why the paint is peeling off
of this green door, but most of them are going to be related to moisture. If
the door wasn't thoroughly painted, then it won't take long for moisture to
seep into any small gaps or cracks, eventually separating the paint from the
door.
However, I've seen this before and would be willing to bet $100
that the bottom of this door was never painted. Eventually over time debris
like leaves and twigs you see on the ground in the picture above got stuck
under the door. This in itself wouldn't create a problem, however wet debris
would.
The wet debris acts like a sponge and if enough debris starts
to decompose around the base of the door, it can actually form a thick layer
at the base of the door and absorb moisture out of the concrete, allowing
moisture to absorb into the wood, regularly.
It's hard to imagine,
but regular maintenance and cleaning probably would have prevented the paint
from peeling off of this door.