It is a question that comes up regularly when homeowners are planning an exterior renovation. The siding needs to be replaced, the windows are aging, and someone mentions that doing both at once might save money. The good news is that in many cases it does, and for reasons that go beyond simple cost savings.
Whether combining window and siding replacement makes sense depends on the condition of each system, the sequencing requirements of the work, and how the projects interact at the wall assembly level. This guide breaks down exactly when and why it makes sense to combine these two projects, and when it does not.
| The practical reason these projects pair well: Both window installation and siding installation require access to the same wall assembly. Scaffolding or ladder setups serve both trades. Flashing details at the window-to-siding interface are critical to moisture management, and coordinating them in a single project eliminates the risk of one trade undoing the other’s work. |
Why Combining Window and Siding Replacement Makes Sense
Shared Setup and Labor Costs
Setting up for exterior work, scaffolding, equipment staging, material delivery, and site protection, costs roughly the same whether a crew is replacing siding, windows, or both. When the projects are combined, that overhead is shared rather than duplicated. Homeowners who complete both projects together typically save 10 to 20 percent compared to scheduling them as separate jobs within a year or two of each other.
The Sequencing Problem: Windows Before or After Siding?
If the projects are done separately, sequencing matters significantly. The correct order is windows first, siding second. New windows must be installed before new siding goes up because the window flanges need to integrate properly with the weather-resistant barrier beneath the siding, and the exterior window trim must be fully flashed before siding panels cover the adjacent wall.
Homeowners who replace siding first and then try to replace windows create a problem. The new siding must be cut or partially removed to access the rough opening, and the flashing integration at the window-to-siding interface must be rebuilt. This adds cost and, if not done properly, creates a chronic leak point at one of the most moisture-vulnerable areas on the wall.
Doing both projects simultaneously eliminates this sequencing concern entirely. The window flanges and siding weather barrier are integrated in a single installation sequence by the same crew or closely coordinated crews.
Moisture Management at the Window-to-Siding Interface
The area where a window meets the surrounding siding is the highest-risk location for moisture intrusion on any exterior wall. Proper flashing at this interface, including sill pan flashing, head flashing, and integration with the weather-resistant barrier beneath the siding, requires careful coordination between the window and siding installation. When both are done together, this detail is executed correctly as a single system. When done separately by different contractors at different times, the interface is more likely to be compromised. For homes that have experienced moisture damage or dry rot behind siding, this interface is often where the moisture originated.
Single Inspection and Permit Process
In many Washington state jurisdictions, combining window and siding replacement in a single permitted project simplifies the inspection process. Instead of two separate permit applications, inspections, and sign-offs, the work is reviewed as a single project. This reduces administrative overhead and keeps the project moving without coordination delays between separate permit timelines.
When Combining Both Projects Does Not Make Sense
There are situations where the two projects are better handled separately:
• The windows are newer and in good condition: If windows were replaced within the last 10 to 15 years and are performing well, replacing them again alongside siding is not justified. Good siding installation can be completed without disturbing well-installed existing windows.
• Budget constraints make one project more urgent: If the siding is failing and causing active moisture damage but the windows are still functional, addressing the siding first is the right call. The windows can follow in a subsequent season when budget allows.
• The projects are on different timelines for other reasons: Insurance claims, HOA approvals, or financing terms may create separate timelines for each project. In this case, ensure the sequencing is windows before siding if they are to be done within a short period of each other.
What the Combined Project Looks Like in Practice
A combined window and siding replacement project typically follows this sequence: rough opening inspection and any repairs needed, window installation with full flashing and air sealing, weather-resistant barrier installation across the full wall, siding installation with proper integration at all window perimeters, and exterior trim and caulking completion. The total project timeline for a medium-sized home is typically 7 to 14 business days. For pricing context on each component, see our guides on window replacement costs and siding replacement costs.
Frequently Asked Questions
Is it cheaper to replace windows and siding at the same time?
Yes, typically. Combining both projects saves on mobilization, setup, scaffolding, and inspection costs. Homeowners generally save 10 to 20 percent compared to completing the two projects separately within a short period of each other. The savings are most significant on homes where scaffolding would be required for both projects independently.
Should windows or siding be replaced first?
Windows should always be replaced before siding if the projects are done separately. The window flanges must integrate with the weather-resistant barrier beneath the siding, and this detail cannot be properly executed after siding is already installed. Replacing siding first and then trying to install new windows requires removing and reintegrating siding panels at every opening.
Can the same contractor do both windows and siding?
Yes, and this is the preferred arrangement for project coordination. A single contractor managing both trades ensures the flashing integration at the window-to-siding interface is handled correctly and that both warranties are held by a single accountable party. Premier Siding and Exteriors installs both replacement windows and new siding, and regularly completes combined exterior renovation projects.
How long does a combined window and siding replacement take?
For a medium-sized home replacing 14 to 18 windows and completing a full re-side, the project typically takes 7 to 14 business days depending on home size, complexity, and whether rough opening or sheathing repairs are needed. Projects with significant repair work take longer. Premier Siding and Exteriors provides a clear project timeline before work begins.
| Thinking About Replacing Both Windows and Siding?Premier Siding and Exteriors manages combined window and siding replacement projects across the greater Seattle area. One contractor, one timeline, one warranty. Free estimates with transparent pricing and no pressure.Call (425) 583-3753 or visit premsidingllc.com to schedule your free estimate. |