96E03/29/06

S716-96E.doc

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  Include the following in all projects which have structural timber
  (treated or untreated).

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**Section 716. - MATERIAL FOR TIMBER STRUCTURES**

**716.01 Untreated Structural Timber and Lumber.** [Delete the first
paragraph and substitute the following:]{.underline}

Conform to AASHTO M 168. Furnish an inspection certification from an
agency accredited by American Lumber Standards Committee as to the
species and grade. Mark all pieces with the inspection service, grade
designation, species, and inspector identity.

Ensure that all structural timber and lumber are seasoned and dried at
the time of fabrication. Material that has become twisted, curved, or
otherwise distorted prior to assembly into the final structure may be
cause for rejection.

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  Include the following in all projects which have treated structural
  timber.

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**716.03 Treated Structural Timber and Lumber.** [Delete the text and
substitute the following:]{.underline}

Furnish wood according to Subsection 716.01. Incise all wood and make
all dimensional cuts and holes in the wood before pressure treatment.
Treat the wood and mark each piece of treated timber according to AASHTO
M133. Treat glued laminated timber members according to AWPA Standards
C14 and C28. Use the type of treatment and minimum net retention of
preservative as shown on the contract drawings.

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  Make sure plans indicate what pressure treatment is acceptable. If none
  is shown on the plans, use aca or copper naphthenate, depending on
  application. See commentary below for discussion of preservative
  treatment alternatives.

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Treat timber members according to "Best Management Practices for the Use
of Treated Wood in Aquatic Environments" (BMPs) as published by Western
Wood Preservers Association (WWPA), latest edition.

All treated timber members shall bear an approved American Lumber
Standards Committee (ALSC) quality mark assuring treatment conforms to
the appropriate AWPA standards.

Provide certification for each lot of treated wood indicating
preservation used, penetration in inches, and retention in pounds per
cubic yard (assay method). Provide written certification that BMPs were
utilized in treating timber members, including a description of the BMPs
used.

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| **716.03 commentary: (text below not to be included as part of the    |
| SCR.)**                                                               |
|                                                                       |
| This subsection in the FP-96 references AASHTO M133 for preservative  |
| treated wood. AASHTO M 133 allows the use of creosote,                |
| pentachlorophenol, ACC, ACA, ACZA, CCA, or ACQ-b. AASHTO further      |
| references AWPA standards, specifically C14, which governs treatment  |
| of wood for highway construction. Acceptable treatments and           |
| retentions are listed in C14 depending on the application (e.g.       |
| ground contract, salt water exposure, handrails, etc.) C14 lists ACC  |
| on being not recommended for any application other than fenceposts,   |
| handrails, and glulam.                                                |
|                                                                       |
| This subsection needs to be modified on a project-by-project basis to |
| allow only those preservative treatments which are acceptable to the  |
| owner and appropriate for the intended application. Following are     |
| some considerations in choosing the appropriate preservative          |
| treatment.                                                            |
|                                                                       |
| Certain species (referred to as \"refractory\" species) will not take |
| oil borne preservative treatment. These include douglas fir from east |
| of the cascades, mountain larch, eastern hemlock, sitka spruce, and   |
| lodgepole pine.                                                       |
|                                                                       |
| Water-borne preservatives tend to result in more severe checking and  |
| splintering of the finished wood. This is largely due to rapid drying |
| before and after treatment. Oil-borne preservatives tend to have less |
| of this problem, in part because the oil residue stabilizes the wood  |
| fibers. If water-borne preservatives are to be used, and checking and |
| splintering are a problem, this should be noted in an "advisory" spec |
| to the treater to take special precautions to minimize rapid drying   |
| of the wood. Kiln drying will generally exacerbate this problem.      |
|                                                                       |
| If the treated wood is to be painted, use either water-borne          |
| preservatives or oxine copper with type c solvent (see below).        |
| Oil-borne preservatives leave a residue on the surface which prevents |
| paint curing and adhesion.                                            |
|                                                                       |
| *Pentachlorophenol (penta)*: long history of effectiveness as a wood  |
| preservative. AWPA C14 lists its use for all applications except salt |
| water. Depending on requirements of the owner, penta is an acceptable |
| preservative for use where there is not likely to be direct human     |
| contact with the treated wood. AWPA standards allow for treatment     |
| using either \"type a\" or \"type c\" solvents. there is always some  |
| potential for bleeding of treatment after the timber is in service.   |
|                                                                       |
| *Ammoniacal copper arsenate (ACA) & ammoniacal copper zinc arsenate   |
| (ACZA)*: both ACA and ACZA are also water-borne preservatives. These  |
| are formulations which were developed specifically to give better     |
| penetration in douglas fir. The ammonia increases the solubility of   |
| copper and zinc and improves the fixation of these metals in the wood |
| fibers. AWPA C14 lists their use for all applications except glulam   |
| treated after lamination.                                             |
|                                                                       |
| To avoid corrosion problems with galvanized hardware, it is important |
| that the treated wood be given adequate time for the ammonia and      |
| moisture to evaporate and the preservative to fixate in the wood      |
| before use. Use of BMP treatment should assure that this occurs.      |
|                                                                       |
| *Chromated copper arsenate (CCA)*: This is a water-borne              |
| preservative. CCA cannot be applied with as much heat as other        |
| preservatives. Because of this, and its mechanical and chemical       |
| properties, it can be difficult to obtain adequate penetration with   |
| CCA in douglas fir. CCA may be used with douglas fir for relatively   |
| small sized members (2x4, 2x6, 2x8). For larger members, use some     |
| other preservative. AWPA C14 lists its use for all applications       |
| except glulam treated after lamination.                               |
|                                                                       |
| *Ammoniacal copper quat - type b (ACQ-b)*: AWPA C14 lists its use for |
| most applications except salt water use, timber piles, and glulam     |
| treated after lamination.                                             |
|                                                                       |
| *Copper naphthenate or Copper-8-quinolinolate (oxine copper)*: these  |
| are both oil-borne preservatives. Neither is listed in AASHTO M133,   |
| but they are listed in AWPA C14 for various applications. Copper      |
| naphthenate is listed in AWPA C14 for use in all sawn lumber and      |
| timber (excludes glulam) except salt water use. Copper nap is very    |
| durable and effective in preventing decay. It can be considered an    |
| acceptable substitute to pentachlorophenol (except in glulam          |
| members). Copper naphthenate typically uses \"type a\" carrier (light |
| diesel oil) which leaves a slight residue on the wood surface and     |
| thus makes this wood unsuitable for painting. Oxine copper is         |
| acceptable for use on hand rails, benches, and similar locations      |
| where toxicity is a major concern, and the timber is not required to  |
| provide long-term structural performance. Oxine copper was developed  |
| during WWII to treat refrigeration storage liners. It is very safe    |
| for human contact. It uses "type c" carrier (mineral spirits) which   |
| evaporate soon after treating and thus leave a dry surface suitable   |
| for painting.                                                         |
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[Add the following subsection:]{.underline}

**716.04 Structural Glued Laminated Timber.** Furnish structural glued
laminated timber according to American Institute of Timber Construction
(AITC) 117. Fabricate according to the combination and grade as
indicated in the contract. Fabricate structural glued laminated members
according to ANSI/AITC A190.1, Structural Glued Laminated Timber.

Manufacture members as industrial appearance grade for wet use
conditions, using a phenol-resorcinol resin type of adhesive throughout.
Use only single- or multiple-piece laminations with bonded edge joints.

Straight or slightly cambered members which are to be loaded
perpendicular to the wide face of the laminates shall be stamped "top"
on the top at both ends of the beam.