Sunroom Addition or Screened Porch Conversion? What We Tell Seattle Homeowners Who Already Have a Porch

By Ruslan Bencheci, Owner and CEO, Star Construction WA. Washington State licensed contractor #STARCCW791L5, bonded and insured. Bothell, WA. Updated August 2026.

If you already have a screened porch, you are not starting from zero, and you are not starting from where you think either.

The question people ask me is whether they should convert the porch or tear it off and build a sunroom addition. My answer is that the porch decides, not the homeowner. Two houses in the same Wallingford block can have porches that look identical from the yard and land in completely different price brackets once I get under them.

So the useful version of this post is not a list of options. It is what I look at, in order, on the first visit, and what each thing means for your budget.

What I check, and roughly in this order

The footings

I go under the porch with a flashlight before I do anything else. What I want to see is concrete piers or a proper foundation, sized right and below frost depth.

What I often find on Seattle porches built between the 1950s and the 1970s is posts sitting on a slab, or on pads that were fine for holding up a screen and a light roof and are nowhere near what a conditioned room needs. Glass is heavy. Insulated walls are heavy. If the footings are undersized, you are pouring new ones, and that single finding moves a project from twenty thousand dollars to something with a four in front of it.

This is the item that reverses people’s plans more than any other.

The ledger and the flashing

Where the porch roof meets the house is where I expect to find rot, and I find it often. Probe the band joist, look at the flashing detail, check the siding above it for staining.

A porch that has been open to the air for forty years dries out after every storm. Enclose it and you change how that assembly handles moisture. If the flashing was marginal before, it will not be adequate after. We correct it either way, but I would rather find it in August than in the middle of a February install.

The roof

Pitch, framing, and whether it drains somewhere sensible. Porch roofs are often framed light because they were only ever carrying themselves.

Here is the good news, and it is the reason porch conversions are frequently worth doing. If the roof structure and the posts are sound, you have the expensive parts already built. Roof and structure are where the money goes on a new build. Screen framing is not, so do not mourn it.

Headroom and floor height

Older porches sometimes sit a step or two down from the house floor, with a ceiling low enough that a finished ceiling assembly would make it feel like a basement. You can work with a step. You cannot easily add height.

The slope

West Seattle, Magnolia, and a lot of the Eastside sit on grades that change the permitting path, which I will get to below.

The three realistic paths

Keep it a porch and do it properly

Re-screen, fix the rot, maybe add a solid roof and better lighting. Cheapest by a wide margin.

I bring this up because sometimes it is the honest answer. If you use the porch four months a year and you are content with that, spending forty thousand dollars to use it eleven months is a want, not a fix. Some people hear that and are relieved.

Glaze the opening

Replace the screen panels with retractable glass and keep everything else. This is where a lot of Seattle porches land, and it is what most of our sunroom and balcony glazing work on existing porches looks like.

You get most of the year back. You keep the ability to slide the whole wall open in July, which a conditioned room cannot give you. You are usually not touching the structure, so the permitting is light or nonexistent. And critically, the footing question mostly goes away, because retractable glass panels weigh a fraction of an insulated wall assembly.

The tradeoff is that it stays a three-season space. Comfortable with a heater into January in this climate, but not a room you would put a desk in for February.

Convert to a conditioned room

Insulated walls and roof, code compliant glazing, permanent heat, permitted as an addition. This is a room, and it counts as living space.

It is also the path where the porch you already have saves you the least. You are typically rebuilding walls, upgrading the roof assembly, replacing footings, and extending mechanical systems. The existing porch contributes its footprint and possibly its roof framing. Sometimes that is meaningful. Sometimes it just tells us where the room goes.

The Seattle permitting detail that decides more than people expect

This is the part I have never seen a national sunroom article get right, so it is worth spelling out.

Small projects in Seattle can go through a subject-to-field-inspection permit instead of full plan review, which is faster and lighter on documentation. SDCI’s STFI permit page lists remodeling a portion of your house and small single-story additions among the qualifying projects.

Two things knock you out of it.

The first is land disturbance. Disturb more than 750 square feet and the project requires a full addition or alteration permit instead. A conversion that stays inside the existing porch footprint often stays under that. New footings, excavation, and drainage work can push you over it faster than you would guess.

The second is environmentally critical areas. If your site has a steep slope, known or potential slide, liquefaction, landfill, or peat settlement issues, exterior work generally triggers a topographic survey and a geotechnical report, and a project that needs those does not qualify for STFI at all. That is a real consideration on a Magnolia bluff or a West Seattle hillside, and it can add months.

None of this means do not build. It means the answer to “how long will this take” depends on your parcel, not on the porch. I check the GIS map before I write a number down. Also worth knowing: once issued, the permit is good for 18 months, which is plenty for this scope but matters if you are phasing work.

Outside Seattle the agencies change but the logic does not. Jobs on Mercer Island and in Redmond go through their own city departments, and we confirm before quoting rather than after.

Why so many Seattle porch conversions stall

Two reasons, and both are avoidable.

The first is that someone quoted the glass and not the structure. A homeowner gets a number for panels, signs, and then discovers the footings during demo. Any quote that has not included someone crawling under the porch is not a quote, it is a guess.

The second is sequencing. People re-roof the house, then decide to convert the porch, and now the new roof has to be opened up at the ledger. If a conversion is anywhere in your five year plan, mention it to your roofer. Same principle applies to deck work, where framing for future glazing at the start costs almost nothing and retrofitting costs real money.

How I actually decide with clients

Three questions, and the porch answers most of them for us.

Is the structure sound below the deck line? If yes, all three paths stay open. If no, the cheap path just got less cheap and the expensive path got relatively more attractive, because you are paying for footings either way.

What do you want to be doing in there in February? Reading with a heater and a blanket is glazing. Working, sleeping, or hosting without a coat is a conditioned room.

Do you want to be able to open the wall? This is the one that decides it for most people, and they usually do not realize it until I ask. A conditioned room is permanently a room. Once people picture giving up the open porch on a July evening, about half of them change direction.

There is no default recommendation here, which is why I distrust anyone who gives you one over the phone.

Frequently asked questions

Can I convert my screened porch into a sunroom in Seattle?

Usually yes. Whether it is a light project or a significant one depends on the footings, the ledger condition, and your parcel. A conversion that keeps the existing footprint and does not require new foundations is often straightforward. One that needs excavation or sits in an environmentally critical area is a different scope and a different permit path.

Is converting a porch cheaper than building a new sunroom?

Often, but not always, and the difference is narrower than people assume. You save on roof framing and posts when they are sound. You do not save much on walls, glazing, or mechanical work. If the footings need replacing, most of the savings disappear.

Do I need a permit to convert a screened porch?

If you are enclosing it as conditioned space, yes. Some conversions qualify for a faster subject-to-field-inspection permit, and some do not, based on land disturbance and site conditions. Simply replacing screen panels with retractable glass on a sound existing structure often does not require one, but we verify with your jurisdiction before quoting.

Will the converted porch count as square footage?

Only if it is built as conditioned space with insulation, permanent heat, and permanent enclosure. A glazed porch with retractable panels does not count, because the system is designed to ventilate. If the square footage number is the point of the project, say so at the consultation, because it changes the build entirely.

How long does a porch conversion take?

Glazing an existing sound porch is usually one day on site after roughly four to six weeks of panel manufacturing. A conditioned conversion is measured in weeks on site, and permitting typically takes longer than construction.

What if my porch has rot?

Very common and not usually a dealbreaker. We scope the repair separately so you can see what is porch repair and what is conversion. Occasionally the rot is extensive enough that rebuilding costs less than repairing, and I will tell you when that is the case.

Start with the crawl, not the catalog

If you are shopping porch conversions right now, the most useful next step is not picking a glass system. It is finding out what is holding your porch up.

Our consultation is free and runs about 45 minutes. I will go under the porch, check the ledger and the footings, look up your parcel, and tell you which of the three paths your structure actually supports. Sometimes that conversation ends with me telling someone to keep their porch and spend the money elsewhere.

Star Construction WA 2220 164th Pl SE, Bothell, WA 98012 (206) 600-2225

We work throughout King and Snohomish counties, including Seattle, Bellevue, Mercer Island, Kirkland, Redmond, Bothell, Renton, Issaquah, Sammamish, Lynnwood, Everett, and Mill Creek. See our sunrooms and balcony glazing service page or get in touch to schedule.

Washington State licensed contractor #STARCCW791L5, bonded and insured. Authorized Lumon dealer for the Seattle metro.