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Re: Wood Beam Repairs

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I suggest cutting out only the portion that is rotted and keep as much of
the existing sound wood as possible, do not lop off the entire end unless
there is no sound material left. In my experience it is typical for the rot
to be puddled on the top and middle of beam with portions of the sides ok,
therefore the rot can  carved out like a squared off canoe and filled with a
glued and screwed "dutchman" . It's a trade off whether you want to hand
treat the existing material with copper green cuprinol (sp) or glue new to
existing. Usual if you hand treat, the glue will not work. It is ideal to
use exterior use glue that the glue lam companies use, but it may not be
available to the public, but you might try calling Standard Structures in
Santa Rosa. Other wise use the best exterior use construction adhesive
available. Sister the rotted member with pressure treated lumber as required
to meet code strength and deflection. Parallams can be purchased for outdoor
use, microlams cannot. You could also consider Alaskan yellow cedar
glu-lams. Lastly you will need to either flash and cope each beam and door
thresholds or plywood (p.t.)sheath and membrane with something like
dex-o-tex. Many times the most common point of leaking is in the pan of
door, which means the entire door may need to be pulled. For waterproofing
problems, I recommend that you have the client hire a waterproofing expert.
The last one I worked on, it was impractical to extend new wood into the
backspan of finished spaces, so we added steel tube diagonal struts to the
foundation, some of the tubes were over 20' long.


Jeff Smith

>Dear fellow engineers:
>Here is the situation:
>Existing (30 years) Balcony, DFL 4x12 beams (exposed,  with redwood spaced
>1x6's) , cantileverded (with back spans into the building). Front prtopn of
>beams have severe dry-rot damage.
>Suggested repair: Cut offf infected portion at a 45 deg angle, add new
>of 4x12 glued to existing, add 2x12 both sides (full cantilever length) and
>staggered bolts.
>Questions: a) What kind of glue should be used (4x12 to 4x12) ?
>                 b) How can I prevent the added 4x12 and 2x12's from future
>dry-rot ?
>                 c) Do exposed Parallams or Microlams resist dry-rot ?
>Your input will be greatly appreciated
>Antonio S. "Tony" Luisoni
>Consulting SE
>aslcse(--nospam--at)  (preferred response address)