blueman writes:
internaughtfull writes:
Hi,

I had some work done on a wooden porch and some dry rot
was replaced with durham's wood putty. It dried for one day then
was painted with valspar ultra latex. It gets wet and peels.

I repainted it and covered it with plastic to allow for drying but
it still peels.

Can I just scrape this and seal it with polyurethane then use
something like Kilz on it? It is a satin white and a small area
so perfect color matching is not that important. Or does the
peeling indicate something else.


While as other posters pointed out, your primary problem is probably
that you didn't let it dry enough...

However, unless you let it dry completely and thoroughly seal all edges
of the wood with an impermeable protective layer and keep it that way
forever, then you will get movement of water in and out. However, most
putties are not really waterproof so they can run into problems with
moisture.

My solution for outside is to always use an epoxy-based product (Bondo
is OK but it tends to be more brittle and not attach as well to wood
which over time results in separation from the wood when it repeatedly
expands & contracts). It's more expensive but should be a more permanent
and professional solution.

If you want something easy, then you might try the following products
from SystemThree:
- First use the RotFix 2-part epoxy to penetrate and solidify the
borders of the rotted area. It is basically a thinned epoxy that
penetrates and plasticizes borderline rotted areas. You let it
seep into the remaining wood and harden. This saves you from
having to cut back too far and is good insurance that you haven't
missed some rot

- Second fill and sculpt the void using the 2-part epoxy Sculptwood
which comes in 2 plastic tubs of putty that you mix by rolling
together into a ball. It is very easy to mold and sculpt. More
importantly, it can easily be sanded and drilled when dry to give
you a seamless repair.

You can buy the SystemThree products in various sizes but like all
epoxies, it's not cheap -- expect to pay ~30-40 for each kit.


Personally, while I still use SystemThree for some uses, I have
"graduated" on to the more versatile West System. It consists of a
single Resin (that I buy by the gallon), various hardeners (differing
mostly in drying speed, but also some specialty ones) and a wide
varierty of different fillers. You really need to see the site for
details.

- For repairing rot, I first use unadulterated resin & hardener
(typically mixed 5:1 for most hardeners) to penetrate and solidify
the remaining wood borders (like RotFix). One could dilute it a bit
with alcahol to get similar viscosity and penetration to RotFix but
tech support at West Systems recommends warming the wood (and/or
the epoxy) as a *better* way of decreasing the viscosity and wicking
in the epoxy (especially with warmed wood) without losing any of the
epoxy strength that dilution would cause.

- For the actual void filling, I add #410 Microlight filler (balloons)
to the resin-hardener mix to get a thick buttery consistency that I
then use to fill the void. You can adjust the thickness of the
mixture based upon your needs. Sometimes I add a bit of my own
sawdust flour but I find that if I use too much of my own sawdust
then the mixture ends up a bit gritty. After drying, you can sand
and drill the patch to make it seamless. You can also use #407 Low
density filler which is denser (and presumably harder) but also a
little more difficult to sand and shape once dry. According to West
Systems, it is recommended to seal coat it with a brushed on layer
of resin-hardener mix since sanding can leave open micropores where
the balloons are sliced open. I have always skipped that step and
have not had any problems.

The Sculptwood putty is a bit easier to apply since it is not as sticky
and goopy but I find that the very stickeness and goopiness of the
Microlight filler mixture gives better adhesion and a more integral
patch even if it is a little messier and requires more sanding when
finished. YMMV.

On the other hand the West System is reported to be an exceptionally
high quality epoxy and to be very versatile and tunable. It is used in
high-end boatbuilding and woodworking. Also, I find it in the long run
to be cheaper since with SystemThree you end up paying epoxy-like prices
for the thinned RotFix solution and for the mostly-filler Sculptwood
putty.

Hope this helps...