Window replacement in Philadelphia, in a city of old rowhouses

Philadelphia is not a market where windows come in standard sizes. It is a city of rowhouses built across a century and a half, in brick openings laid by hand, in a housing stock old enough that the rules about how the work has to be done are as much a part of the job as the windows themselves. Census figures have put the median year built here around 1949, with a majority of units predating 1950 — among the oldest housing of any large American city. That single fact drives almost everything below: what is behind your existing sash, what a contractor is legally required to do about the paint, and why two honest quotes on the same block can look nothing alike.

No two openings, and almost no standard sizes

In a postwar suburb, a window company measures one opening, confirms the others match, and orders a stack of identical units. In a Philadelphia rowhouse that assumption breaks immediately. These openings were built into masonry by hand, often decades before dimensional standardization meant much, and a house can easily have three or four different sizes across two floors — sometimes with a quarter-inch of variation between openings that were meant to be the same.

The practical consequence is that most Philadelphia jobs are custom-sized rather than pulled from stock, and that a contractor who quotes from a doorway glance rather than measuring every opening individually is guessing. Ask directly whether the price assumes stock sizes. On a rowhouse the honest answer is usually no, and a quote built on the wrong assumption is a quote that changes later.

What is actually behind your original sash

If your rowhouse still has its original wood double-hung windows, they almost certainly run on a rope-and-weight counterbalance: an iron weight hanging on a cord inside a hollow pocket built into the frame on each side. That pocket is why the old sash glides. It is also a void running the height of the opening, alongside the wall, frequently with little or nothing in it.

This is the single most consequential thing about a Philadelphia window job, because it forces a real decision. An insert window drops a new unit into the existing frame and leaves that pocket sealed up behind it, untouched. A full-frame replacement takes the old frame out entirely, which exposes the pocket so it can be insulated and air-sealed, but costs more and disturbs more of the surrounding trim and plaster. Neither is automatically right. Our guide on full-frame versus insert replacement walks through how to decide, and in this city the weight pocket is usually the deciding factor rather than an afterthought.

Drafts that are not coming from the window

A common Philadelphia experience: new windows go in, and the room is still cold near the wall. Often that is because the draft was never coming through the glass. It was coming around the frame — through the weight pockets, through gaps between an old wooden frame and the brick it sits in, or through failed mortar joints in the masonry surrounding the opening.

An insert replacement can leave every one of those paths intact. That is not a reason to avoid inserts, which are the right call in plenty of houses, but it is a reason to ask a contractor specifically what they intend to do about air sealing at the perimeter, and whether they have looked at the condition of the mortar around the opening. If the answer is only about the window unit itself, the draft may well survive the installation.

Lead is a legal requirement here, not a formality

Federal law treats any home built before 1978 as potentially containing lead paint, and in Philadelphia that covers the overwhelming majority of the housing stock. Under the EPA's Renovation, Repair and Painting rule, a firm doing this kind of work on a pre-1978 home must be EPA Lead-Safe Certified and must use lead-safe work practices.

There is a small-job exemption in that rule — for minor repair and maintenance under roughly six square feet of disturbed painted surface indoors, or twenty square feet outdoors — and window replacement does not qualify for it. The EPA is explicit that window replacement is always a covered activity regardless of square footage. So on a typical Philadelphia rowhouse, a contractor replacing windows without lead-safe certification is not cutting a corner on process, they are working outside the rule. Ask for the firm’s certification and expect containment, careful cleanup and no dry sanding or open-flame paint removal on the job.

Whether you need a permit — and the one case where you do

Most homeowners are surprised by this one. The Department of Licenses and Inspections (L&I) does not require a building permit for replacing doors and windows in one- or two-family dwellings, as long as the work is a like-for-like swap: same location, same size opening, no change to the framing or the masonry.

The permit requirement appears when the scope goes past that — enlarging or reducing the rough opening, cutting new masonry, or altering structure. In that case a building permit does apply, and L&I’s filing fee for a one- or two-family dwelling is $25, plus a $3 city surcharge and a $4.50 state surcharge, with the permit fee itself scaling to the work. Two practical points follow. First, a contractor telling you a routine same-size replacement requires an expensive permit is worth questioning. Second, if a design calls for a bigger opening — which comes up often when a bedroom window is being brought up to egress size — that is a permitted job and should be priced and scheduled as one.

If your house is on the Philadelphia Register, that comes first

This is the exception that swallows the permit answer above. If your property is on the Philadelphia Register of Historic Places, or sits inside a designated historic district, the Philadelphia Historical Commission has to approve exterior changes before the work happens — and windows, storm windows, shutters and doors are named explicitly among the features it reviews.

Two things homeowners usually get wrong about this. It is free: the City charges nothing for a project review by the Commission or its staff. And it is not automatically slow — the City says staff approve the large majority of building permit applications, over 90 percent, without sending them to a full Commission hearing. What review does affect is product choice, since replacements are generally expected to match the character of the original in material and profile, which narrows the field well before price enters the conversation. The Commission can be reached at (215) 686-7660 or preservation@phila.gov, and it is worth calling before you take quotes rather than after, so every contractor is bidding the same thing.

Why Philadelphia quotes spread so far apart

Homeowners here routinely collect estimates that differ by a factor of two or three on the same house, and conclude someone is lying. Usually nobody is. Four local variables move the number hard, and they are rarely spelled out on the quote: whether the units are custom-sized to hand-built masonry openings or assumed to be stock; whether the job is full-frame or insert; whether lead-safe work practices and containment are actually priced in; and whether historic-district requirements have narrowed the product to a wood or clad-wood unit rather than vinyl.

Access adds a fifth. A third-floor front window on a narrow street with no side yard, no driveway and cars parked bumper to bumper is a materially harder install than the same window in a detached house, and a bid that ignores that has not accounted for the labor it will actually take. Our guide on what replacement windows actually cost breaks down what belongs on a legitimate quote — the point in Philadelphia is to get every bidder specifying the same four variables, because otherwise you are not comparing prices at all.

Check the PA number before you sign anything

Pennsylvania requires anyone performing more than $5,000 of home improvement work a year to register with the Attorney General’s office under the Home Improvement Consumer Protection Act. Registration issues a unique Pennsylvania Home Improvement Contractor number — a PA# — and the law requires that number to appear on advertisements, contracts, estimates and proposals used in the state.

That gives you a thirty-second check that most homeowners skip: the PA# should be printed on the estimate in front of you, and its status can be verified through the Attorney General’s home improvement contractor registry, or by calling the office’s helpline at 1-888-520-6680. A missing or unverifiable PA# on a written estimate is a clear signal to stop. Our guide on hiring a window company without getting burned covers what else belongs in the contract before a deposit changes hands.

ZIP codes we cover in Philadelphia

19102, 19103, 19104, 19106, 19107, 19109, 19110, 19111, 19112, 19113, 19114, 19115, 19116, 19118, 19119, 19120, 19121, 19122, 19123, 19124, 19125, 19126, 19127, 19128, 19129, 19130, 19131, 19132, 19133, 19134, 19135, 19136, 19137, 19138, 19139, 19140, 19141, 19142, 19143, 19144, 19145, 19146, 19147, 19148, 19149, 19150, 19151, 19152, 19153, 19154

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