A Brief Summary by S&A of:

APTI Article, Vol XXXVIII No. 2-3, 2007 Page 36, by Mr. Ronald W. Anthony.

Introduction:

3 Primary Reasons to Conduct a Wood Inspection

1. Concerns about moisture and it’s effects.
2. Deterioration, both physical and biological.
3. Need to determine material properties.

Highly Variable Wood Behavior

1. Different species.
2. Rate of tree(Measured in Growth Rings per Inch).
3. Age of tree.
4. How the wood was cut from the log.
5. Presence of defects.
6. End use conditions.

 Concerns About Moisture

1. Paint peeling, stains, warping.
2. Active leaks.
3. Decay + insects associated with moisture.
4. Moisture measurement.

Concerns About Deterioration (Weathering)

1. Results of weathering, overload failure, mechanical failure, shrinkage.
2. IMPORTANT: Checks can be o.k. Checks in structural members that “meet” are of concern.
3. Differential shrinkage in mortise & tenon can lead to failure.
4. Weathering of Wood: Cyclic wetting and drying, exposure to UV light & erosion by windblown debris.

Concerns About Deterioration (Biological)

1. Fungal or insect attack.
2. Bacteria degradation possible but not common in historic buildings because fungi + insects act more rapidly.
3. During inspections – focus on fungus and insect activity.
4. Be aware of moisture absporption through endgrain. Internal mositure retention causes decay, and not always visible.
5. Inner growth rings better resist decay.
6. Mildew: Grows on surface – does not damage wood.
7. Stain Fungi: Propogates through wood but does not cause effect strength.
8. Decay Fungi: (Alert Here) Breaks down wood composition. Types include: Brown Rot, White Rot, Dry Rot. It is important here to identify location and extent of rot.
9. Incipient Decay: (Early stages of decay) Discoloration + initial loss of integrity of wood. Use an awl or screwdriver to discover soft or punky wood.
10. Intermediate Decay: Small voids have developed.
11. Advanced Decay: Tools to measure interior decay – Incriement borer, hand drill. More advanced technique – Resistance drilling, to determine extent of damage.
12. Termites: Detection by presence of mud tubes.
13. Wood Boring Beetles: Create holes packed with “frass.”
14. Carpenter Ants + Bees: Leave large open holes.
15. For both insect and damage and decay, effective cross section properties of the members can be determined and used for structural analysis.

Material Properties

1. Determine wood species.
2. Tools for Wood Inspection: 1. Visual inspection 2. Sharp probe 3. Moisture Meter 4. Telescoping mirror and flashlight.
3. Visual ID’s: MIssing or broken pieces, fungal decay, moisture.
4. Probe ID’s: Internal voids.
5. Moisture meter: provides approximate values.
6. Conductance meter (Resistance Moisture Meter): Used for heavy timbers. This method is useful for determining whether the wood is drying or taking up moisture.

Advanced Investigative Techniques

1. Stress wave analysis: Location of advanced decay.
2. Resistance drilling: Quantify loss of material.
3. Digital Radioscopy: View hidden conditions.

Where to Look

1. Wood in contact with the ground.
2. Wood exhibiting moisture stains.
3. Wood with visible decay.
4. Roof penetrations.
5. Attic sheathing, framing lumber and timbers.
6. Sill beams and wall plates, particularly when in contact with masonry.
7. Floor joists and girders, particularly where resting on exterior walls.
8. Openings (doors and windows)
9. Material interfaces.
10. exterior woodwork.
11. porches.
12. crawl space and basements.
13. areas of structure that have been altered