Wood Deck Structural Evaluation for a Residential Property in Wisconsin

The Concern

The property owner needed engineering input regarding the structural integrity of an exterior wood deck at a residential property in Oshkosh, Wisconsin. The concern focused on visible deterioration and whether the deck framing, supports, and connections were performing as intended.

Because exterior decks are exposed to moisture, freeze-thaw cycles, and long-term weathering, visible surface deterioration can sometimes be connected to deeper structural issues. StructSolve’s role was to evaluate the readily observable components and document the conditions that could be seen during a non-invasive engineering observation.

Why StructSolve Was Contacted

The project called for a structural engineer report rather than a general repair opinion because the observed conditions involved several parts of the deck system. The review was not limited to the walking surface. It also included framing members, support points, wood shims, concrete support columns, railing support conditions, and joist connections.

StructSolve was asked to provide a clear engineering perspective on the observed structural concerns and recommended next steps. The evaluation did not include destructive testing, removal of finishes, or review of concealed elements, so the report was based on accessible and visible conditions at the time of the observation.

What StructSolve Observed

StructSolve documented significant moisture-related deterioration in portions of the wood deck framing. The report noted that some decking boards showed deterioration and should be replaced. Supporting joists and framing members were identified for continued evaluation, especially if symptoms such as increased movement or a bouncy feeling developed over time.

The rim board was a key concern. Deterioration at this component had progressed enough that the report identified replacement as warranted in affected areas. Because the rim board helps support and transfer loads at the deck perimeter, deterioration there can affect how the deck performs.

The stair railing post also showed significant rot at its base and was recommended for replacement. StructSolve also observed through-cuts in a set of joists, which appeared to have been made for utilities that were no longer present. Although signs of distress were not identified at the time of observation, the report recommended reinforcing those members with adjacent joists and proper joist hanger support.

Support conditions were another important part of the evaluation. Concrete support columns showed weathering and surface deterioration. One column appeared out of plumb and may have experienced settlement. Untreated wood shims were observed between several concrete support columns and the deck framing, and at least one shim showed moisture-related deterioration and compression under load. The report also identified localized crushing beneath a center support column and noted that supporting wood framing in that area likely experienced weather-related rot.

StructSolve also documented a support post at the south side of the deck that was not engaged with the deck framing. The post was free-standing, lacked a mechanical connection, and was not transferring load at the time of the observation. In another location, a joist was face-nailed to the rim board and showed noticeable deflection at the connection, indicating that the connection did not provide adequate load transfer.

Engineering Assessment

The observations pointed to multiple related deficiencies in the exterior deck system. StructSolve’s report described concerns involving moisture-induced deterioration, improper load transfer, inadequate connections, and support conditions that required correction or monitoring.

The evaluation was limited to visible and accessible components, so concealed conditions were not opened or evaluated. The report did not claim that repairs had been completed or that concealed components were free of concern. Instead, it identified observed issues and separated the recommendations into significant concerns, moderate concerns, and preventative maintenance items.

This distinction helped clarify which conditions required more immediate repair planning and which items should be monitored or maintained to reduce further degradation.

Remedial Actions

StructSolve’s report included several specific remedial actions. Decking boards showing fungal decay were recommended for removal and replacement. The rim board was also recommended for replacement in affected areas to help restore structural capacity where deterioration was present.

For the joist that had been face-nailed at the connection, StructSolve recommended installing an approved joist hanger to provide better connection capacity and improve load transfer. The report also recommended establishing a positive connection between the disengaged wood post, its footing, and the deck framing so that the support could participate in the load path.

Where deck joists had been cut for utilities, StructSolve recommended reinforcing the affected members by installing adequately sized adjacent joists with proper hanger connections. This recommendation addressed the reduced continuity of the cut members without claiming that concealed conditions had been fully evaluated.

The untreated wood shims between the concrete columns and deck framing were recommended for replacement with preservative-treated wood or non-compressible materials such as galvanized steel plates. This recommendation addressed durability and stable load transfer at the support points.

Preventative maintenance items included repointing concrete support columns where surface deterioration was present and monitoring the concrete column that appeared to show possible settlement. StructSolve also recommended periodic monitoring of the deck framing, with deteriorated or weakened members replaced or reinforced as needed.

Outcome

The structural report gave the property owner a clearer understanding of the visible deck conditions and the recommended repair priorities. The findings identified deteriorated wood components, deficient support conditions, and connection issues that should be addressed by qualified repair professionals.

The deliverable also helped separate immediate repair recommendations from longer-term monitoring and maintenance items. That distinction supported practical next-step planning without overstating the outcome or assuming that repairs had already been completed.