We have two large exterior exposed cypress beams/posts, that are part of th
e structural wall and roof support of a breakfast nook area (back patio are
a) that have developed rotted bottoms. I've been putting off this repair
because I'm not sure, exactly, what might be the best/proper repair. Obvi
ously, moisture has wicked up the posts for some time, and the bottoms are
Left and right side posts, scroll left:
We've started demolition of part of the back patio, for the construction of
a pergola, spanning this breakfast nook wall area. I need to repair the
se posts, soon. I'm not sure how far/deep, into the wall, the rot goes, bu
t I suspect maybe half way through the cross section of the post. I'll pr
obe it, later. Before I probe (gouge out, cut into) the post, I would like
to know what possibly might be best for the repair..... I wouldn't want to
have removed something, if it could be part & party to the repair.
It would be very difficult to remove and replace the beam, since they are p
art of the support structure, but if need be, that will be done. I'd pref
er to repair at least the bottom, for now, unless sunsequent discovery of v
ery extensive damaged is found. There is no plinth under these beams.
I had thought of epoxy, since I more recently learned some of the virtues o
f epoxy use; I've thought of bondo; THought of patch-replacing parts of the
I've thought of the wood hardening products, for rotted wood, like this one
Home depot, Lowes and other outlets have similar wood hardening products, b
ut I don't know anything about these products and I'm not sure which brand/
product is the best for this kind of structural support, weight bearing use
I'd appreciate any and all input, for this repair.
We have other posts on an side porch, that are supported on plinths, that h
ave bottom rot, also. These posts can be easily replaced, but I'd prefer,
for now, to repair the bottoms. They are stained with a paint-like stain,
so bondo may be an option for repairing/filling voids, if need be. The por
ch roofing is cantelevered, but the posts do supply some support for the po
rch, because of heavy tiles (1500 lbs/square) on the roof. Any advice woul
d be appreciated for this repair, also. Scroll left for another pic.
If you're not concerned about the current structural integrity and
want to stop the deterioration where it is, try looking around
<http://www.rotdoctor.com . I've used a number of these products with
good results. It's not a wood replacement, though.
We have two large exterior exposed cypress beams/posts, that are part
of the structural wall and roof support of a breakfast nook area (back
patio area) that have developed rotted bottoms. I've been putting
off this repair because I'm not sure, exactly, what might be the
best/proper repair. Obviously, moisture has wicked up the posts for
some time, and the bottoms are rotten.
Left and right side posts, scroll left:
We've started demolition of part of the back patio, for the
construction of a pergola, spanning this breakfast nook wall area.
I need to repair these posts, soon. I'm not sure how far/deep, into
the wall, the rot goes, but I suspect maybe half way through the cross
section of the post. I'll probe it, later. Before I probe (gouge
out, cut into) the post, I would like to know what possibly might be
best for the repair..... I wouldn't want to have removed something, if
it could be part & party to the repair.
It would be very difficult to remove and replace the beam, since they
are part of the support structure, but if need be, that will be done.
I'd prefer to repair at least the bottom, for now, unless sunsequent
discovery of very extensive damaged is found. There is no plinth
under these beams.
I had thought of epoxy, since I more recently learned some of the
virtues of epoxy use; I've thought of bondo; THought of
patch-replacing parts of the beam.
I've thought of the wood hardening products, for rotted wood, like
Home depot, Lowes and other outlets have similar wood hardening
products, but I don't know anything about these products and I'm not
sure which brand/product is the best for this kind of structural
support, weight bearing use.
I'd appreciate any and all input, for this repair.
We have other posts on an side porch, that are supported on plinths,
that have bottom rot, also. These posts can be easily replaced, but
I'd prefer, for now, to repair the bottoms. They are stained with a
paint-like stain, so bondo may be an option for repairing/filling
voids, if need be. The porch roofing is cantelevered, but the posts
do supply some support for the porch, because of heavy tiles (1500
lbs/square) on the roof. Any advice would be appreciated for this
repair, also. Scroll left for another pic.
You are between a rock and a hard place.
First things first.
Bondo is a polyester based putty thickened with talc.
It's about as useful as a set of breasts on a boar hog.
It has limited adhesive properties. (Ever wonder why body repair
punch holes, then putty the holes over with Bondo?)
Products like git-rot, rot-doctor, etc, have been around for ever.
They are basically very low viscosity epoxy injected into rotted
wood to create a rotted wood core stabilized with epoxy.
Good structural results are at best mediocre.
Plinth construction is about the only way out if you want to sleep at
Support the structure with jack posts, Cut off rotted bottom 'till
you reach solid wood. Build masonry posts/supports from ground up to
wooden post. Prevent wood from directly contacting masonry so it
cannot absorb moisture.(using moisture barrier of some sort - best to
put wooden posts on metal (stainless or hot galvanized)saddles rather
than directly on concrete - put trim around post to "hide" the saddle
and cover the necessary gap.
DO NOT use "bondo". It is not structural, and polyester auto body
filler is not waterproof - it acts like a sponge - particularly the
normal talc-filled crap.
Epoxy is better, but filling rotten wood with epoxy still leaves you
with rotten wood..
says it sucks
up water. I don't know how long I have used Bondo but it has been several
decades and I have never found either of those negatives to be true.
I have a couple of bottom rotted, exterior door jambs that were repaired
with Bondo at least ten years ago. Still good. As Lew said, Bondo is
polyester resin filled with (mostly) talc. To my knowledge, cured polyester
doesn't "suck up water" and talc is about the least liquid absorbing mineral
around which is why it - in rock form - is/was the choice for chemlab work
There is no doubt in my mind that filled epoxy is better than Bondo.
Nevertheless, for just a cosmetic repair, I would use Bondo...it can be set
up and sandable in minutes vs the hours for epoxy.
Actually, polyester is notorious for doing exactly that.
Google for "polyester blistering" and you'll find 1000s
of articles on the problem.
As for the original problem, I'd agree with those who
suggest cutting off the affected part, and installing
some sort of plinth. There's really no way to treat
rot other than replacement.
I've seen my share of blisters but the ones I have seen have been between
layers of laminate or separation of the laminate from a surface.
I DAGS and the best page I found is relative to fiberglass/polyester resin
on boats from the link below. I have copied and pasted some excerpts, CAPS
are added to draw attention.
All said and done, I wouldn't worry about using Bondo as a rotted/missing
wood repair :)
Further observation shows that bottom laminate constructed with the
commonly used orthophalic resins has a LIFE EXPECTANCY OF AROUND 30 TO 35
YEARS before deterioration due to blistering and resin damage has
structurally weakened the bottom laminate. This deterioration can often be
observed as flexing of the bottom laminate when hand pressure is applied
even on boats in the 40' to 50' range.
Fiberglass blistering is caused by one or more factors such as resin type,
contamination of materials, trapped gases, built-in voids, poor wetting out
of laminate, incorrect humidity or temperature and dry layup. Osmotic
fiberglass blistering is a process which depends on the temperature of, and
exposure time to, the water. Given the above mentioned factors, it is not
surprising that fiberglass blisters appear on a large number of vessels
which are KEPT AFLOAT FOR LONG PERIODS OF TIME IN RELATIVELY WARM WATER.
FIBERGLASS BLISTERS FORM ONLY WHEN WATER PENETRATES TO THE LAMINATE. THIS
WATER NOT ONLY DAMAGES THE LAMINATE BY FORMING BLISTERS CAUSING LOCALIZED
DELAMINATION BUT ALSO COMBINES WITH UNCURED WATER SOLUBLE AND HYDROSCOPIC
COMPONENTS IN THE RESIN FORMING AN ACID SOLUTION WHICH IS HIGHLY CORROSIVE
TO EVEN THE WELL CURED POLYMERS IN THE RESIN. As more water reaches the
laminate, more corrosive solution is formed and more resin broken down. The
effect is that of flushing the resin out from between the fiberglass
strands. A laminate so affected is often referred to as having been
That speaks to fiberglass laminates - not polyester body filler.
Go to the Bondo web site. Mondo.com, and their TIPS page.
Quote: " Is body filler water resistant?
Yes. Water absorption tests show that filler only absorbs 0.3% of
water,which is considered minimal. Therefore, body filler is not
waterproof by itself but is water resistant. Note: If the application
is primed and painted, the paint will render the application
The fact that it needs to be primed and painted to make it waterproof,
and generally the backside of a rustout repair in NOT primed and
painted, meats water can still be absorbed into the filler from behind
- and when that water entrenched in the polyester filler freases, it
pops off of the metal, and out of the repair. It might not be a
problem in Arizona - or alabama or florida - but it is a very real
problem here in "the north".
There is a reason they also make a fiberglass filled body filler,
which IS advertized as being "waterproof". If you look at their How to
for rust repair they use "bondo-glass" for the initial repair to fill
and seal the hole. This is their "waterproof" product. Then they have
you finish the repair with "bondo body filler" which is the poyester
body filler you guys are talking about. When fixing a dent their How
To has you filling with "bondo body filler", preparing the bare metal
surface with a 36 grit disc to allow the bondo to stick.
In my first reply I asked Sonny if he wanted to make a strucrural or
cosmetic repair. If structural, I said replacement or reinforcement. For
cosmetic, I mentioned several ways including Bondo. For any filling of a
cosmetic repair of rotted wood, one has to dig out the bad wood.
Just going from years of experience with body work and my late
brother who was a bodyman half his life. A hole was always filled with
either a brazed/welded/soldered metal patch or an epoxy/fiberglass
patch before filling with polyester body filler if you wanted it to
stay firmly attached long term. That's why Lew says it doesn't stick
well. Also, it will not stick well to a perfectly smooth surface - you
always rough up the patch area with 80 or 40 grit sand paper before
applying bondo if you want it to stay stuck.It needs a mechanical
"tooth" to stick well. (which is also why a "hack" bodyman will punch
a dent full of holes to extrude the "bondo" into to give it a fighting
chance of staying in.
The newer "light" fillers that use glass microbeads instead of talc
stand up better to moisture, and epoxy or UV Cure fillers are even
When I hear "bondo" I think cheap polyester body filler - and I make
sure it is well protected from moisture in use..
I wouldn't waste my time with fillers or stabilizers. If you want it to
last, replace the posts.
I can't tell for sure from the pictures, but the one that has the propane
tank looks like the bottom of the post may have already been replaced at
some point. About a foot from the bottom the grain doesn't line up.
The exposed posts would be fairly easy to replace. Just use a bottle jack
and a shorter post to jack up the structure slightly. Don't go crazy
jacking it up, you just want to take the load off the existing post. Then
cut the old post out and install a new one. Ideally you should install a
metal post base at the bottom of the post to prevent water from wicking up.
Barring that, I would at least put some tar paper or sill sealer under the
post as a water barrier. Not ideal, but better than nothing if you're not
going to use a post base.
The ones that are inset into the structure are going to be a bit more work.
You may have to cut the structure away from the posts, then jack up and
replace. You will most likely need to repair wall surrounding the posts
afterwards. I don't know how it's all put together but it may be easier
just to take the wall down and rebuild it after replacing the posts.
On Sunday, April 5, 2015 at 11:36:25 AM UTC-5, Swingman wrote:
, HerHusband wrote:
Yeah, I was hoping for an easy out, an easy fix, but I figured there was no
No previous repairs. It's all one continuous post, salvaged hand hewn beam
s. Those misalignments are the result of the hewn marks, when squaring the
I need to figure out how to seal the bottoms. I don't recall sealing the
bottoms, when initially installed. We just treated the faces as best we c
ould, once installed. It'll be major reconstruction to replace the beams.
About the only part not attached to the other framing menbers is just insi
de the exterior walls... we packed the uneven cracks with backer rods, rath
er than using caulk. Maybe this spacing, though packed, was deficient, al
lowing moisture to enter, but there is no evidence of moisture damage along
the walls (that we can see), just at the bottom of the beams. No eveidenc
e of moisture entrance on the inside of the room.
Thanks to all.
Seal with thinned varnish, in two or three applications.
But more important is a way to block wicking, so that dampness in
whatever the post rests upon cannot creep up the post over time. They
make special cast aluminum post bottoms for this purpose. One can also
make one from metal stock.
Just for clarification: "posts" are the vertical structural members that
hold up horizontal "beams".
You keep mentioning "beams" so I'm not sure if you are having other
issues beyond the wicking at the bottom of the posts?
Unless you have wiring or something running through the posts, you can
probably just use a reciprocating saw with a long blade to cut the nails
between the wall and the posts. Then jack up the stucture above and slip
out the posts.
I'm not sure what the best way to reattach the walls to the post would be
during installation though. You would probably need to remove some of the
interior wall covering to drive in some long screws or something.
Lag bolt a stout block of wood to the posts in the wall so you have
something to jack against with two bottle jacks and a stout cross piece
to keet the jacks away from the work area. Cut away all rotten wood,
make a plinth at least 1" above grade and scarf in new wood with at least
an 8:1 joint using epoxy and lag bolts. Bed the foot on epoxy + glass
cloth, or mastic + roofing felt to seal it. If the original post was in
a hole, the new plinth needs locating pegs with corrisponding holes in
the post bottom which should be strong and non-corroding. e.g. stainless
or bronze allthread or thick GRP dowel. Assemble the scarf last so you
can fit the new piece over the pegs onto the bedding The same will work
for the other posts, but you dont need the jacking piece as you can jack
against the roof beam and I'd through bolt the scarf.
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
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