On 8/28/2013 6:10 PM, Peabody wrote:
I have some large fir beams that stick out from under the roof line, and they
have deteriorated. The beams were last painted with exterior latex paint,
which didn't work very well in keeping the moisture out. So I'm going to be
digging out the rotted parts and putting in filler.
Without details or a photo, I suspect that getting the wood DRY enough
for any paint will be the greatest challenge. Are the beams structural
or just decorative? Fastened how? Next to stucco or ?

But some portions of the beams are still ok, for now. Do I have to remove
all of the latex paint, and then put on an oil-based primer/sealer in order
to get good protection?

You would not normally remove paint that is not loose and is on sound
surface.

Or would it be possible to leave the good parts as
they are, but cover them as well as the repaired portions with a latex
primer? I see that Valspar has a latex primer, and perhaps there are others
that would work.

There are gazillions of primers that would "work"....most importantly,
for a problem area, pick a good brand of paint from a good paint store.
A paint store in business for a good length of time will most likely
give good advice about how to go about this, from the bottom up.

It would be very difficult to remove all of the old latex. The beams are
quite rough, with lots of raw wood texture, and I'm concerned that even with
a chemical stripper I wouldn't get all of it out. And you know, if possible
I'd like to not make a career of this.

I would not consider a chemical stripper...too messy, too expensive.

I should say that in the end the beams will be painted with the same exterior
latex paint I'll use for the trim. So I guess I was just hoping I could find
a way to stay with latex all the way through, and avoid issues of what I can
paint over what. But I'm just not sure that will work for a fir beam
sticking out in the rain. I have made metal caps for the beams from gutter
stock, and that may help some.

I would appreciate any suggestions on how to proceed.

Oil and water don't mix when they are liquid. Oil/alkyd is generally
favored for wood exteriors. No reason you can't use both, on different
areas with matching colors. Again, a good paint store can mix and test
your colors, including drying. If the match isn't absolutely perfect,
it may not show.

I don't know how often people use pressure washing prior to painting
wood (all I know of p.w. was for stucco in Florida). A wash with bleach
(dilute) may be advisable....got to have dry weather and dry wood. As
someone else said, end grain needs extra coats...it absorbs quickly and
there won't be a secure paint film until the end grain is filled...three
coats there, probably.

Here is a link to Sherwin Williams (all of the top paint co.'s have
pretty good help sites, as well as email contacts):

http://www.sherwin-williams.com/home...sture-outside/