Is it cheaper to replace siding and windows at the same time?

Usually, yes. Trim, flashing, scaffolding and setup are paid for once, and you avoid cutting into new siding later. Ask contractors to price the combined project and each part separately to see the difference for your house.

Which should be done first, windows or siding?

Within a combined project, the old siding comes off first, then the windows go in with new flashing, then the weather barrier, trim and siding. If you are doing only one now, siding usually protects the house more unless the windows are leaking or rotted.

Can new siding be installed around old windows?

Yes, if the windows are in good condition. The installer should replace the flashing and trim around them and leave room for a future window replacement.

Does replacing windows need a permit?

Often, yes, even where re-siding does not. Rules vary by state and city, and in Florida windows also need product approval. Your contractor should know the rules and pull the permit.

Replacing Siding and Windows at the Same Time

Why the two projects belong together

Most water that gets into walls enters around windows and doors. Keeping it out depends on how the window’s flashing, the weather-resistive barrier (house wrap) and the siding trim overlap: each layer has to lap over the one below it so water runs down and out, never in. When windows are replaced in a sided wall, the installer has to work that flashing into a barrier that is already covered by siding. When siding is replaced around old windows, the new barrier has to be tied into old flashing that may already be failing.

Doing both at once lets one crew – or two crews in sequence – build that whole detail new: sill pan, window, flashing tape, house wrap, trim and siding, in the right order. It is the single best argument for combining the projects.

What you save by doing both at once

Trim and capping once. Window trim, J-channel and capping are installed only once, around the new windows. Nationally, window trim and flashing work typically costs $1,500 to $3,000 as a separate line item on a siding job.
Scaffolding and setup once. Ladders, scaffolding, dumpsters and protection of plants and driveways are paid for once.
No cutting into new siding later. Replacing windows a few years after new siding means removing and reinstalling siding around every opening – and matching panels that have already weathered.
One permit and one inspection where permits are required.

How much that saves depends on the house. Ask contractors to price the combined project and each part separately so you can see the difference.

What the two projects cost

Project	Typical range	Source
Vinyl siding replacement, 1,250 sq ft (national)	nearly $18,000	Cost vs. Value 2025
Fiber cement siding replacement, 1,250 sq ft (national)	about $21,485	Cost vs. Value 2025
Vinyl window replacement, ten windows (national)	about $22,073; about 76% recouped at resale	Cost vs. Value 2025
Window trim and flashing on a siding job (national)	$1,500–$3,000	Angi / This Old House

Cost figures are published averages and ranges for orientation only – not quotes. The contractor you are connected with measures your home and sets the price.

Combined, a whole-house siding and window project on a typical home comes to roughly $40,000 to $44,000 at these national average prices, so it is worth planning carefully. Siding tends to return a higher share of its cost at resale than windows: in the 2025 Cost vs. Value Report, vinyl siding recouped about 97% and fiber cement about 114%, compared with about 76% for vinyl windows.

The right order of work

Measure and order. Windows usually have the longest lead time, so they are ordered first. The siding product and trim profile should be chosen at the same time, so trim depth matches the new window frames.
Remove the old siding on the walls being worked on, and inspect the sheathing, especially below windows where rot is most common.
Replace the windows as new-construction or full-frame installations where possible, with a sloped or flashed sill, flashing tape at the sides and top, and the head flashing lapped correctly.
Install the weather barrier over the whole wall, lapped over the lower flashing and under the head flashing, so water always runs out.
Install trim and siding, with J-channel or trim boards sized to the new windows and the siding.

If the window installer and the siding installer are different companies, agree in writing who is responsible for flashing and for any leak around the windows. The best outcome is one contractor responsible for the whole wall.

Signs your windows should be part of the job

Soft or rotted wood at the sills or the bottom of the frames
Water stains on the wall or floor below a window
Fogging between the panes of double-glazed windows (a failed seal)
Sashes that stick, will not stay open or let in drafts you can feel
Single-pane windows or original windows from before the 1980s
Windows you already plan to replace within the next five years or so

If several of these apply, combining the projects is usually the smarter choice: replacing windows after new siding means reopening the wall around each window. If the windows are sound, a careful siding installer can protect and re-flash them instead.

Energy: what to expect

New windows and new siding with a sealed weather barrier both cut air leakage, and combining them lets the installer seal the joint between window frame and wall – one of the leakiest spots in older houses. Be realistic about savings, though: siding itself adds little insulation unless you choose insulated vinyl or add foam board, and window savings depend heavily on what you are replacing. Comfort – fewer drafts and cold spots – is often the most noticeable improvement.

When it makes sense to split the projects

The windows are newer (roughly within the last 10–15 years) and in good condition – the installer can tie the new siding into them carefully, and you can replace them later with a less invasive insert installation
Budget: if you can only do one, siding usually protects the house more, because it covers the whole wall; failing windows that leak or have rotted sills are the exception
Different urgency: storm-damaged siding may need to be replaced now, while windows can wait

If you split the work, at least replace the flashing and trim around the old windows during the siding job, and ask the siding installer to leave enough room around the windows for a future replacement.

Permits and rules to keep in mind

Window replacement often needs a permit even where re-siding does not – for example, in Pennsylvania, vinyl and aluminum siding on existing homes is excluded from the Uniform Construction Code, but window work is not automatically exempt; in Florida, windows need product approval and impact protection in many areas. On homes built before 1978, both window and siding removal disturb painted surfaces, so the contractor must follow the EPA’s lead-safe rules when more than 20 square feet of exterior paint (or any window replacement) is disturbed. In Pennsylvania and New Jersey, make sure the contractor is registered with the state and that both parts of the job are in one written contract.

Should you replace siding and windows at the same time?