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 Structural Damage Probing - wood structure assessment
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Wood damage assessment in buildings: this article describes methods for inspecting, probing, and otherwise assessing wood structures and wood components (floors, trim, sheathing) for damage by insects or rot. We describe when, where, & how to inspect & probe wood components on buildings when damage (carpenter bees, carpenter ants, termites, powder post beetles, fungal damage, rot damage) is seen, known, or suspected.
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How to assess the extent of structural damage from wood destroying insects
Assessing the extent of structural damage to wood framing members in a conventional building inspection involves the following phases and procedures:
Visual inspection to locate evidence of insect damage or structural rot
Watch out: Don't assume only one kind of insect damage will be present as the same conditions that invite one insect into a wood structure may invite others. We have found termite damage, carpenter ant activity, and powder post beetle damage all in the same structure, on occasion even in the same wood beam or joist. Our photo (above right) illustrates wood rot found in the same floor joist where there was extensive termite damage.
Selection & use of probing tools to test wood components for insect damage or rot
Using an appropriately-chosen instrument (see below) probe suspect or visibly damaged wood beams, joists, rim joists, sill plates, even flooring or subflooring; we start this step in basements and crawl spaces but may find evidence to justify probing finished materials such as interior trim or wood floors.
Professionals use a wide variety of wood probing instruments of different end-diameters, sharpness, and, importantly, length, as it can be difficult to reach some surfaces that really should be examined. Our photo (above left) illustrates using a simple screwdriver, (my dad's), to probe an area of visible termite damage. And at above right, our pen is probing suspected rot damage at wood siding. An example of probing a finished hardwood floor is at TERMITE INSPECTION & DAMAGE.
Watch out: building inspectors and PCOs should never probe nor use destructive inspection methods without permission of the building owner. Make certain that you have explained the justification for any inspection techniques that involve risk of damage, even just cosmetic damage to the structure. However, in our OPINION, if your finger or pen easily penetrate insect or rot damaged trim, flooring, or other indoor finished surfaces, you have not caused actional damage to that component; rather, you have disclosed it.
We arbitrated an ugly case in which a novice home inspector left screwdriver blade jam marks throughout the finished area of a new home. Don't do that.
The depth to which a wood probing instrument will penetrate wood depends on these factors
- The hardness of the wood being tested. At above left our photo illustrates micro-drilling, courtesy of Paul Probett, Incodo Forensic Building Specialists [1]. At above right you can see the butt end of our screwdriver, buried to the hilt in a termite-damaged sill plate located at the base of an interior partition in the basement of a New York home. The screwdriver penetrated this sill with virtually no effort.
- The condition of the wood: water content, and most significantly the extent and depth of insect damage (or rot) nto the wood. This step is key in assessing powder post beetle damage as it is difficult to know before probing whether the damage is superficial ("topical") or much more extensive.
Our screwdriver penetrating the floor joist (photo at left) confirmed extensive termite damage in this joist that formed the ceiling over a basement utility room whose partition wall sills were also termite infested (photo above right). Finding damage in both floors and ceilings of this home continued the trail of disclosure of a very extensively damaged structure.
Many inspectors and some engineers use rules of thumb about probe entry depth to form an opinion about the remaining strength of the structural member and whether or not it needs replacement. See TIMBER ASSESSMENT for details about microdrilling, an engineering approach to assessing the strength of damage-suspect structural wood.
- The cross section and area of the tip of the probe. Using a sharp pointed ice pick to probe wood is ridiculous as the pointed tip will penetrate just about any wood and will make unnecessary holes and damage.
Our fine wood probe (shown at below left) was made by grinding off the sharp point of the ice pick to a flat end. We use this probe delicately and in discrete locations such as at the bottom of wood trim in unobtrusive areas of suspected damage.
- The force applied to the wood test probe. Except for the use of instrumented microdrilling (see TIMBER ASSESSMENT) this step involves some subjectivity and is based on the experience and knowledge of the inspector.
Examples of probing wood for structural damage
Clearly the ground-off ice pick wood probe (far left) is finding less-severe damage than the "to the hilt" stab of my dad's screwdriver demonstrated by our client (close left).
Watch out: while we advise against unwarranted cosmetic damage at a building interior, strategic probing of wood sills, rim joists, or floor structures (or other wood members) can disclose severe structural damage that was otherwise not evident. At below left, even our pen was able to easily puncture this termite-damaged joist that had been "cosmetically-repaired" using wood putty
At below left we illustrate an appropriate use of our fine wood damage probe in an area of suspected cover-up of a termite damaged oak floor framed at ground level with no other access below.
When observing the termite damage at below right, probing adjacent wood members as well as along the length of the visibly attacked members is completely appropriate.
And at below right our termite damage photograph illustrates a serious risk: this floor joist looked "perfect" from its exterior, but probing disclosed that it was severely damaged - basically a "hollow skin" of wood. The light colored marks at the upper edge of the joist (and suspected termite activity from other site clues) led us to probe this joist bottom where it rested on the sill plate. Leverng the screwdriver disclosed the damage our photo illustrates.
Demolition or removal of materials for further inspection for WDI damage: when is it justified?
Demolition or removal of materials for further inspection for insect damage may be justified and necessary. Usually powder post beetles have attacked wood beams, typically rough cut lumber or round "trees" used as joists or beams or sills in older homes. We don't usually need to remove flooring or siding to access and assess such damage, but there are cases where it may be needed.
- Inaccessible crawl areas: In some cases such as where there is an inaccessible crawl space we may need to make inspection or access openings to the crawl area, either from outside the building or even from indoors.
- Buckled, crushed building siding: siding buckled at ground level over an inaccessible crawl space or slab on grade (photo, below left) is a likely indicator of severe hidden rot or insect damage to the buildng's sills and floor structure. Further inspection from outside is usually justified. Even siding buckled atop a foundation wall above ground may indicate a risk of crushing sills that merits further investigation such as our cement asbestos siding photo (below right).
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- Additional materials removal during building repairs can also be expected to disclose damage from insects, rot, or mold. In general we remove damaged materials until there is a suitable safe margin of clean un-damaged materials, extending that distance of removal of wood framing where necessary for structural reasons (replacement of an entire member for practical or cost reasons) or in special cases such as MERULIPORIA FUNGUS DAMAGE (photos shown just below) we remove wood for a larger safety margin, as much as two meters beyond visible damage due to hidden fungal infections.
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
 Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' home inspection education products include
- The ASHI-adopted Home Inspection Training Program, and Commercial Building Inspection Courses
- The Home Inspection Home Study Course, and publications such as
- The Home Reference Book, a reference & inspection report product for building owners & inspectors.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a ten percent discount on any number of copies of the Home Reference Book purchased as a single order. Just enter HRBUS10 in the order payment page "Promo/Redemption" space.
Note: InspectAPedia.com ® editor Daniel Friedman is a contributing author.
- The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones
- Home Inspection Report writing materials, including the Horizon Software System that manages business operations, scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones.
- The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors
- [4] Brick Development Association, The Building Centre, 26 Store Street, London, WC1E 7BT, England, U.K., Tel: 020 7323 7030, Email: brick@brick.org.uk
- [5] Brick Industry Association, 1850 Centennial Park Drive, Suite 301, Reston, VA 20191
Phone: 703.620.0010 Fax: 703.620.3928.
- [6] Canada Masonry Centre, 360 Superior Blvd., Mississauga ON Canada L5T 2N7. Tel: (905) 564-6622. Offers the CMCA Textbook of Canadian Masonry.
- [7] "Concrete Slab Finishes and the Use of the F-number System", Matthew Stuart, P.E., S.E., F.ASCE, online course at www.pdhonline.org/courses/s130/s130.htm
- [8] Sal Alfano - Editor, Journal of Light Construction*
- [9] Thanks to Alan Carson, Carson Dunlop, Associates, Toronto, for technical critique and some of the foundation inspection photographs cited in these articles
- [11] Terry Carson - ASHI
- [12] Mark Cramer - ASHI
- [12] JD Grewell, ASHI
- [14] Duncan Hannay - ASHI, P.E. *
- [15] Bob Klewitz, M.S.C.E., P.E. - ASHI
- [16] Ken Kruger, P.E., AIA - ASHI
- [17] Aaron Kuertz aaronk@appliedtechnologies.com, with Applied Technologies regarding polyurethane foam sealant as other foundation crack repair product - 05/30/2007
- [18] Bob Peterson, Magnum Piering - 800-771-7437 - FL*
- [19] Arlene Puentes, ASHI, October Home Inspections - (845) 216-7833 - Kingston NY
- [20] Greg Robi, Magnum Piering - 800-822-7437 - National*
- [21] Dave Rathbun, P.E. - Geotech Engineering - 904-622-2424 FL*
- [22] Ed Seaquist, P.E., SIE Assoc. - 301-269-1450 - National
- [23] Dave Wickersheimer, P.E. R.A. - IL, professor, school of structures division, UIUC - University of Illinois at Urbana-Champaign School of Architecture. Professor Wickersheimer specializes in structural failure investigation and repair for wood and masonry construction. * Mr. Wickersheimer's engineering consulting service can be contacted at HDC Wickersheimer Engineering Services. (3/2010)
- [24] *These reviewers have not returned comment 6/95
- [25] Superior Walls of America, Ltd, 937 East Earl Road, New Holland, PA 17557, Phone: 1-800-452-9255, Fax: 717-351-9263. Website: http://www.superiorwalls.com/ Technical support:
Ed Helderman our Codes and Standards Manager. Email: ehelderman@superiorwalls.com or 717-351-9744
Robert Hare, Director of Technical Operations, rhare@superiorwalls.com, Tel: 717.351.9735
Thanks to Robert Hare for technical critique & content suggestions for this article - August 2010
- [26] Superior Walls of America Builder Guideline Booklet MAN 42-9000 booklet, [local copy] web-search 09/01/2010 original source (indirect link): http://www.superiorwalls.com/faq.php?&answers=1&details=53
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Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
 The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.
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