Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

Re: Wood Adhesives

[Subject Prev][Subject Next][Thread Prev][Thread Next]
"Robert Fennema, P.E." wrote:

> I am designing a detail to correct a construction defect. The
> contractor failed to install blocking and boundary nailing at the top of
> the shear walls perpendicular to the roof rafters. This is only one of
> the many shear transfer connections omitted from this 12,000 SF home.
> Of course the roof covering is on. It is a two piece clay tile system
> set in mortar.  We would like to repair the defect without removing the
> roof covering to install the missing boundary nailing.
> Am considering gluing a 2 x 4 block flat onto the underside of the OSB
> roof sheathing and connecting it to a new block on the shear wall using
> an A35. I need help selecting the adhesive that would substitute for
> the lack of boundary nailing.  Does anyone know the shear transfer
> values of various adhesives that might be available?  I guess this would
> be expressed in # per sq in.
> Is this an acceptable idea?

The major type of adhesive used in the engineered wood product industry is
either a Phenol Formaldehyde (PF) or Phenol Resorcinol Formaldehyde (PRF).
An other adhesive used is Monodiisocyanurate (MDI).  When I worked for Trus
Joist MacMillan and field repairs were made with an adhesive, we typically
used a PRF.  One that we used in repairs, and I used in a Master's thesis
was Penacolite, manufactured by Indspec Chemical Corporation located in
Pittsburgh PA.  It's a waterproof two part adhesive manufactured in
accordance with ASTM D 2559.  Indspec manufactures a couple types of PRF,
but I used resorcinol phenol formaldehyde polymer liquid resin G-1149-A and
powdered paraformaldehyde hardener G-1131-B.  The mixing is easy and it can
be applied with a brush or roller.  AITC A190.1-1992 specifies a minimum
shear strength of 1075 psi and a minimum of 80% wood failure for adhesives
used in the manufacture of Glulam for example, and PRF is typically used.  I
was bonding a pultruded carbon fiber plate (CFRP) to LVL and in testing of
block specimens got an average shear stress of 945 psi.  The adhesive
generally performs well in wood repairs, but requires a minimum clamping
pressure when curing, which is sometimes difficult to achieve, given field
conditions.  Sorry I don't have an address for the company but they be on
the web.