Getting Bids for Rot Repair: How to Manage Siding and Dry Rot Restoration

Managing rot repair and siding replacement on multi-unit properties presents a unique procurement challenge for homeowners associations and building owners. When the full extent of hidden dry rot damage is unknown until siding is removed, obtaining accurate fixed-price bids becomes difficult. This practical guide explains how to structure the bidding process for building repair and maintenance projects with concealed conditions, offering strategies for combining fixed-price and time-and-materials contracts to control costs while ensuring quality workmanship.

Understanding the Scope of Rot Repair Projects

Dry rot in exterior walls typically originates from prolonged moisture exposure due to failed flashings, inadequate housewrap installation, or deteriorated caulking around windows and doors. When siding is removed, the damage often extends well beyond what is visible from the exterior. Sheathing may be soft or completely decayed, framing members may need sistering or replacement, insulation may be waterlogged, and window frames or doors may require replacement. For more details, see damp proof course installationThe hidden nature of this damage makes it nearly impossible for contractors to provide a guaranteed fixed price without including a large contingency.

For a typical 75-unit townhouse project, the total repair cost can range from $300,000 to $400,000 or more, depending on the extent of concealed damage. At this scale, the difference between a reasonable bid and an inflated worst-case estimate can be hundreds of thousands of dollars. Associations must approach the bidding process strategically, balancing the need for cost certainty with the reality that unknown conditions will inevitably arise once work begins.

The first and most important step is a thorough pre-bid investigation. Hiring a qualified third-party consultant with expertise in exterior leakage and moisture damage is money well spent. By removing selected siding panels, trim pieces, and interior drywall at strategic locations, the consultant can characterize the typical damage patterns, estimate the percentage of units affected, and identify the root cause of the moisture intrusion. This information allows contractors to base their bids on real data rather than assumptions, reducing the contingency markup.

Structuring a Hybrid Fixed-Price and Time-and-Materials Bid

The most practical approach for rot repair projects is a hybrid contract that separates known work from unknown work. The known portion, such as siding removal and replacement, new housewrap installation, flashing repairs, and painting, can be bid as a fixed price. Contractors can estimate these items with reasonable accuracy based on the building dimensions and the specified materials. A detailed scope of work and material specifications should be provided to all bidders to ensure apples-to-apples comparisons.

The unknown portion covers rot repair to sheathing, framing, insulation, and windows that cannot be fully assessed until the siding is opened. For this portion, a time-and-materials or unit-price contract is more appropriate. Contractors bid fixed rates per square foot for sheathing replacement, per linear foot for framing repairs, and per unit for window replacement. These unit prices can be capped with a not-to-exceed total, giving the association cost control while allowing the contractor to be paid fairly for the actual work required.

Bid documents should require contractors to provide detailed breakdowns of their hourly rates, material markups, and overhead percentages for the time-and-materials portion. This transparency allows the association or its construction manager to audit invoices and verify that charges reflect actual conditions in the field. Requiring daily field reports with photographs of all rot discoveries further strengthens oversight and minimizes disputes when change orders are necessary.

Selecting and Managing a Construction Manager

For projects exceeding $100,000, hiring an independent construction manager, engineer, or architect to oversee the work is strongly recommended. The construction manager prepares the bid documents, prequalifies contractors, evaluates bids, administers the contract, conducts site inspections, and approves progress payments. This professional oversight is particularly valuable for rot repair projects where the scope changes as hidden damage is uncovered, because the manager serves as an impartial referee between the owner and the contractor.

The construction manager should have specific experience with exterior leakage investigation and repair. This is a specialized niche within the construction industry, and general residential contractors may not have the deep knowledge of flashing details, water-resistive barrier systems, and window integration needed to prevent the same problems from recurring. The cost of a construction manager, typically 8-15 percent of the project value, is offset by savings from competitive bidding, reduced change orders, and better quality control.

When selecting a construction manager, request references from at least three similar multi-family exterior repair projects. Visit completed projects if possible, and ask about the manager’s approach to documenting concealed conditions, handling disputes, and ensuring that repairs address the root cause of moisture intrusion rather than just the visible symptoms. A good manager will also help the association evaluate warranty options and establish a long-term maintenance plan for the building envelope.

Preventing Future Rot Through Proper Building Envelope Design

The most cost-effective rot repair is the one you never have to do. Once the current repairs are complete, investing in a properly designed and installed building envelope will prevent recurrence. The critical components include through-wall flashings at all floor lines and window heads, continuous water-resistive barriers lapped shingle-fashion over flashings, and properly detailed window and door openings with pan flashings and weep systems. These details are frequently done wrong in new construction, leading to the very problems now being repaired.

The choice of siding material also affects long-term durability. Fiber-cement siding, when properly installed with adequate clearances above grade and at roof intersections, offers excellent rot resistance. Hardieplank and similar products carry 30-year warranties against rotting and cracking. However, even rot-resistant siding will fail if the underlying water-management details are incorrect. The siding is the last line of defense, not the first. The primary defense is the drainage plane behind the siding, which must be free-draining and connected to flashings that direct water to the exterior.

For the 75-unit townhouse example, a comprehensive post-repair maintenance program should include annual inspections of the building exterior, focusing on sealant joints, flashing terminations, and grade clearances. Gutters and downspouts must be kept clean and free-flowing to prevent water from backing up under the siding. With proper design, quality installation, and routine maintenance, a well-repaired building envelope should provide 30 to 50 years of service before significant rot issues reappear.

Recommended Bid Structure for Rot Repair Projects