I am looking for some insights from anyone out there who has some experience
with repairing large beams with dryrot. The beams look like they are about
16-18" tall, 12" wide and probably 35-40' long. They reside underneath an old
country store, are made of fir and it looks like none of the rot goes completely
through the beams, although a couple go a little over half way. The largest
rotted area thus far covers about 5-6' of the length, about 50% through in the
middle, tapering out to zero on the ends of the 5-6' sections. The bad sections
are almost exactly in the middle of the span. I cannot see or measure any sag
thus far, but I want to shore up the bad spots before it starts sagging. I
already know the cause of the rot I need some ideas on good repair techniques to
restore the "cancerous" areas. Thanks in advance for any tips you can pass
along. regards, Joe.
Rotted wood is gone, there is no repair. You will have to add "sisters" (ie
patches) to the bad areas.
Depending on the usage and loads, you should be able to keep using the
Don't do it yourself, get at least two estimates from experienced
On Fri, 27 Mar 2009 03:52:19 +0000, Lew Hodgett wrote:
Oh, I don't know. I've had the same problem twice, on a workshop floor
and a porch, and I fixed it myself both times.
I bought "sister" beams the same size as the rotting ones. I got them
long enough to reach piers as well as the solid portions of the old beams
and attached them to the old beams with lag screws.
One such repair was 5 years ago, the other 10. So far so good.
Intelligence is an experiment that failed - G. B. Shaw
Nothing wrong with Larry's fix ... particularly since the sisters spanned
the same piers as the old beam.
When possible, LVL's are a good choice for sisters; they come in various
sizes, are lighter, and can be "laminated" together with a nailing pattern
to make a bigger beam, which makes them easier to get into tough spots.
Simpson strapping is often also required to attach the sisters to the faulty
beam, and the piers.
Sistering a beam is a perfectly acceptable repair, as long as you do it to
code or have it vetted by an engineer. By supporting the ends of the
sisters on piers he's being quite conservative.
My main concern with the beams in question would be the size of
them--they're heavy enough that if they get away from you they can do some
serious damage and if they're going into a confined space then some
specialized fixturing might be needed to move and position them safely.
It's one thing when you and a hundred Amishmen are carrying one on your
shoulders, it's quite another when it's you and a long ton of beam in a
Yeppers..._IF_ (the proverbial "big if") this really is that massive a
structure and loadings are anything approaching what it must have been
designed for it definitely needs an engineer's evaluation if the
expected continued usage is anything like that.
OTOH, if it is an old industrial/manufacturing building and is now
simply being used as nothing more than a light fabrication or store,
it's quite possible even as they are they're more than adequate and
nothing would actually be required to be done.
Either needs a competent structural evaluation imo if there's anything
significant going to be done to make it worth the investment as well as
the all-important issue of safety when dealing with anything of that size...
They were cleaning up to remodel an old grocery store in town on the
square. The workers heard some creaking. They ran out of the building.
The building collapsed. I thought I read termite infested. They hauled
away the rubble, tore out the old slab and built a new buidling.
On Thu, 26 Mar 2009 16:54:47 -0800, Joe Brophy
There's nothing you can do that will restore anything other than the
exterior appearance w/ patching.
You have only the basic choice of either adding sufficient shoring
underneath via pilings or similar (w/ the attendant adequate foundation
support for them, of course) or adding other structural material in a
way tied to the solid portions of the existing beams to carry the other
For something the size you're talking about, that would be a healthy
beam in it's own right other than steel plate bolted thru or similar.
In a beam of that size, it would be possible I would think to engineer a
bottom tension rod that could be attached on both sides of the damage
area, but anything approaching an optimum solution would take an
engineer to evaluate and design both the structure and the attachment
As others have said, you cannot make a structural repair by
smearing bondo, wood filler, epoxy, etc on the beam. If you have
intentions of an alternate method to carry the loads you can make
a decorative repair of the finishes. You might also consider
interior columns or a pair of cross beams to catch those timbers
back where they are not hurt..
Keep the whole world singing . . . .
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