How to Draw the WDI Inspection Graph
Why this matters
The graph is the part of a wood destroying insect report that outlives everyone's memory of the inspection. Months later a buyer finds damage behind a bathroom wall, the lender's file is pulled, and the only thing that says where you looked, what you found and what you could not reach is a sketch drawn in a crawlspace on a clipboard. A graph with no north arrow, a slab addition drawn as part of the crawl, or a finding marked "rear" turns a defensible inspection into an argument. This card owns drawing it: measuring the footprint, adding the structures, and keying every finding so another inspector could walk to it. What each field on the written form means is owned by 'The WDI Report Form, Section by Section'; the inspection itself is in 'Wood Destroying Insect Report Inspection'.
What the graph has to carry
Whatever form your state or the lender requires, the graph does the same work:
- The outline of every structure inspected, with dimensions, close enough to scale that proportions are right.
- A north arrow, so "north wall" on the report means one wall.
- Foundation type by section. Crawl, slab, basement. Houses with additions are often two or three of these, and each changes what you could see.
- Attached structures: porches, stoops, decks, garages, patios, and anything else touching the house.
- Access points: crawl access, attic access.
- Every finding, by symbol and by number, the number matching the numbered item in the written report.
- Every inaccessible area, marked as such, with the reason on the report.
Use the symbol legend your form prints, if it prints one, so a reviewer used to that form reads you correctly. Where it does not, use a fixed shop legend and draw it on every graph.
Measuring the footprint
Measure the exterior, wall by wall, going around in one direction. A long tape or a laser measure, starting at one corner and recording each wall segment as you go. Write each length on the sketch as you take it, not afterwards from memory.
Close the loop. On a house built from right angles, the lengths running east-west on the north side add up to the lengths on the south side, and the north-south lengths on the east side add up to the west side. If they do not, you missed or misread a segment. This check takes thirty seconds and catches the most common graph error, an offset or bump-out that got skipped.
Round to the nearest foot. The graph is a locator, not a survey. A finding marked on a wall that is within a foot or two of where it really is can be found; a wall that is the wrong length by six feet puts every finding on it in the wrong place.
Draw at a consistent scale on graph paper or the software grid, one square to one or two feet. Freehand outlines drift, and a drifting outline makes the findings drift with it.
Building the graph, step by step
1. Outline the main structure from your measurements, with each wall length written on it.
2. Add the north arrow, from a compass or the phone, not from the street name.
3. Add attachments and additions with their own dimensions. Show where they meet the house, because the joint between a slab addition or porch and the original foundation is a classic entry point.
4. Label the foundation type of each section. Write CRAWL, SLAB or BASEMENT inside each part.
5. Mark access points. CA for crawl access, AA for attic access.
6. Place findings as you find them, not at the truck. Each gets a symbol and a number at the exact location on the wall or in the plan. Write the number and a short description on the clipboard list right then.
7. Hatch the inaccessible areas and number them too, so the report can say why each was not inspected.
8. Cross-check numbers against the written report before you sign it. Every number on the graph has a report entry, and every report entry has a number on the graph. The reviewer checks the same thing again before the report goes out, per 'The WDI Report Review and Issue SOP'.
Locating a finding precisely
A symbol on a wall is only as good as the reference it hangs from. Give every finding a distance from a named corner, measured in the field, and use the same reference in the report text: "north wall, 14 ft east of the northwest corner" can be found with a tape; "rear of house" cannot. For a finding out in the crawl, away from the perimeter, give distances from two walls, or tie it to something fixed that will still be there, such as a pier, a drain line or the crawl access. When a finding runs along a wall, give where it starts and its length, so the graph shows a segment rather than a point.
Worked example: a crawl house with a slab addition and a porch
The house. Main structure on a vented crawlspace, with a slab-on-grade family room added on the north side at the east end, and a concrete front porch on the south side.
Measurements, going around counterclockwise (east first) from the southwest corner. South wall 52 ft. East wall: 28 ft of main house, then the addition's east wall continuing north 12 ft, so 40 ft on the east side. Addition north wall 16 ft. Addition west wall 12 ft back south to the main house. Main house north wall 36 ft running west. West wall 28 ft back to the start. Front porch: 20 ft along the south wall, 8 ft deep.
Closing the loop. East-west: north side 16 + 36 = 52 ft against south 52 ft. Closes. North-south: east side 28 + 12 = 40 ft against west side 28 + 12 = 40 ft, where the 12 is the addition's west wall. Closes.
Findings during the inspection.
- Inactive mud tube on the inside face of the foundation and soil-packed galleries in the sill plate, about 3 ft, on the main north wall below the hall bathroom, roughly 14 ft east of the northwest corner.
- Elevated wood moisture at the subfloor under the kitchen sink drain, about midway along the main house, near the north wall.
- Area under the front porch slab: no access; the slab abuts the foundation for its full 20 ft.
- Slab addition: finished walls and floor covering, slab edge concealed by flooring and trim inside and by soil and landscaping outside; framing not visible.
The graph:
16 ft N
+---------+ ^
| 4 ///// | |
12 | ADDITION| 12
| SLAB |
36 ft | /////// |
+---------1XD-------+---------+
| [bath] 2M |
28 CRAWL | 28
| CA |
+-----+------------------+----+
| 3 /// PORCH SLAB |
+------------------+ 8
20 ft
52 ft
X evidence D damage M moisture
/// inaccessible CA crawl access
What it lets a stranger do. Finding 1 sits on the main north wall, between the northwest corner and the addition, and the report puts it about 14 ft from that corner below the bathroom. Finding 2 sits near the north wall under the kitchen. The porch (3) and the whole addition (4) are hatched, and the report says why: no access under the porch slab, finished and concealed construction in the addition. A second inspector, a repair contractor or the buyer's attorney can stand in the crawl and walk to finding 1.
What the earlier draft got wrong. The first pass at the truck drew the outline from the two longest dimensions, a plain 52 by 40 rectangle, with the addition inside it. The closure check would not have caught that, because a rectangle always closes. What caught it was step 4: writing SLAB inside the addition made it obvious the rectangle was claiming 16 by 12 ft of crawl that does not exist, and a reviewer reading the graph would have asked why the crawl findings never reached that corner.
Common graph errors and the check that catches each
| Error | What it causes | Check |
|---|---|---|
| Skipped offset or bump-out | Every finding on that side lands in the wrong place | Close the loop on both axes |
| No north arrow, or north by street | "North wall" means different walls to different readers | Compass, every graph |
| Addition drawn as same foundation | Claims inspection of areas that do not exist or were not visible | Label foundation type per section |
| Finding with a symbol and no number | Report entry and mark cannot be matched | Number cross-check before signing |
| Inaccessible area not marked | Reads as inspected and clean | Hatch and number every limit |
| Findings added at the truck | Locations drift to "about there" | Mark at the spot, as found |
What changes the method
Detached structures. Whether a detached garage, shed or fence is in scope depends on the form your state or the lender requires and on the agreement. If it is in scope, it gets its own outline and dimensions on the same sheet with its position relative to the house. If it is out of scope, say so on the report rather than leaving it off silently.
A basement with finished and unfinished parts. Draw the basement plan, hatch the finished walls as inaccessible, and place findings on the unfinished walls.
Software sketches. Fine, if they carry the same items. Check the exported image keeps the numbers legible; a graph that prints too small to read the numbers has failed at its one job.
The finish test
Hand the graph and the report to another inspector who was not there. Without asking you anything, they can point to every numbered finding on the house, say which foundation each section sits on, find the crawl access, and name every area that was not inspected and why. If they have to ask, the graph is not done.
References
- See related: The WDI Report Form, Section by Section
- See related: Wood Destroying Insect Report Inspection
- See related: How to Probe and Sound Wood for Hidden Termite Damage
- See related: The WDI Report Review and Issue SOP
- The form your state or the lender requires, including its printed symbol legend