Finishing the basement: what the bid should include

A finished basement is extra floor you already own, which is why the bid looks cheaper than a room addition until someone adds a bathroom, a legal bedroom, and the waterproofing you skipped.

“Finish the basement” is not one product. An open rec room with LVP and cans is a different job from two bedrooms, a full bath, and a wet bar.

You’re finishing a basement. Moisture, electrical, plumbing, and an egress cut in the wall are hire work. Painting and click-together flooring can wait.

$30 to $50 per square foot

HomeGuide’s 2026 basement guide puts finishing at $30 to $50 per square foot, or $15,000 to $75,000 for 500 to 1,500 square feet. An open plan is the low end of each row; three rooms is the high end.

An 800-square-foot open finish is $24,000 to $32,000; the same size with three rooms is $32,000 to $40,000. A 1,000-square-foot open plan is $30,000 to $40,000. One basement bedroom, on their room table, is $3,000 to $12,000 before you add a legal way out.

HomeGuide: cost to finish a basement

Angi’s 2026 article lands the same $15,000 to $75,000 band, average about $32,000, with a wider $2,800 to $100,000 if you count the cheap partial and the full gut.

Their per-square-foot table is lower ($7 to $23), which is why two “finished basement” quotes can be $20,000 apart and both be “average.” Ask what is in the number.

Angi: cost to finish a basement

Cost to Renovate’s 2026 project page is tighter: most jobs $10,000 to $40,000, national average around $22,000, $15 to $60 per square foot.

Their mid example is an 800-square-foot finish with a half bath. Premium is 1,000 square feet with a full bath, wet bar, and a bedroom with an egress window.

Cost to Renovate: basement finishing

Use HomeGuide when the bid is priced per square foot with rooms. Use Cost to Renovate when someone is selling a $12,000 “finish” that has no bath, no moisture work, and no permit. Angi’s $32,000 average is a sanity check, not a target.

Moisture, a bath, a bedroom

Moisture first

HomeGuide puts waterproofing at $1,900 to $6,300. Angi puts a typical waterproofing add around $4,400, or about $5 to $10 per square foot.

Cost to Renovate flags interior waterproofing $2,000 to $5,000 and says skipping it is how you pay $3,000 to $10,000 later to tear finished walls out.

If the contractor wants to frame next week and has not talked about water, find someone else.

A bathroom

HomeGuide’s basement bath addition is $10,000 to $25,000. Cost to Renovate splits a half bath $3,000 to $6,000 and a full bath with shower $6,000 to $12,000, plus $1,500 to $3,000 if you need a sewage ejector because the drain sits above the sewer.

“We’ll rough it in” is a real line ($500 to $1,000 on their save list). “Bathroom included” without a shower, an ejector, or a permit is not.

A bedroom that is actually a bedroom

That means egress, usually a window in that room, not a pretty slider that does not open far enough. HomeGuide lists an egress window at $2,000 to $5,000. Cost to Renovate puts each one at $2,500 to $5,000 installed, because you are cutting the foundation and adding a well.

Angi’s window materials-and-install band of $200 to $950 is the glass, not the hole in the wall. Budget the cut.

Heat

HomeGuide: $5,000 to $11,000 to get heat into a finished basement, more with new ducts. Angi quotes HVAC work around $2,000 to $3,000 on some jobs, which is a small add, not a system. Finished space that counts on an appraisal usually has to be heated. Ask which.

Headroom

HomeGuide says basement ceilings need to be at least 7 feet. If yours are not, that is a raise-the-house bid, not a finishing bid.

Does this bedroom need an egress window?

If someone will sleep down there, plan on an emergency escape and rescue opening in that room. The International Residential Code (IRC R310) is the model most towns start from.

A typical list looks like this. Net clear opening 5.7 square feet, or 5.0 if the window is at grade. Clear opening at least 24 inches high and 20 inches wide. Sill no more than 44 inches off the finished floor. Openable from the inside without a key or a tool.

If the window is below grade, a well with about 9 square feet of area and at least 36 inches out from the wall, plus a ladder if the well is deeper than 44 inches.

A 20-by-24 opening is only 3.3 square feet. It fails the area rule even though it hits the width and height minimums. The inspector measures the hole you can actually climb through, not the sticker on the frame.

Local amendments win. Some places want an egress in any finished basement, bedroom or not. Some existing houses get different rules than new construction.

The question for the contractor is: will this room be permitted as a bedroom, and which opening is the legal way out? If they say “the stairs count,” get that in writing from the building department, not from the salesperson.

This is layout and code, not a medical opinion. A legal bedroom is a permit category.

How will they handle moisture?

How will they handle moisture? Test, drain, membrane, sump, dehumidifier. “It looks dry today” is not a plan. Angi puts a sump around $575 installed; that is cheap next to ripping out carpet.

What’s the use? Open rec room, office, legal bedroom, bath, kitchenette. Price those as separate lines.

If a bedroom is on the plan, name the window, the well, the ladder, and the permit.

What’s the ceiling height after flooring and a dropped soffit around the ducts? Measure 7 feet where people walk, not in the middle of the room under a beam.

HVAC and electrical: whose load, whose panel, whose inspections. HomeGuide’s electrical band for a basement is $2,000 to $13,500.

Plumbing: gravity drain or ejector. Rough-in now vs finish later.

Who pulls the permit: building, electrical, plumbing. Unpermitted finish is a resale and insurance problem.

Insulation against the concrete. Cost to Renovate’s useful tell: rigid foam on the wall, then the studs, not fiberglass batts against damp masonry.

Get two bids that answer the same list. An $18,000 open-plan finish and a $55,000 two-bedroom suite are both “finishing the basement.”

Wet wall, a hopper window, carpet on a weeping slab

Drywall on a wet wall

The cheapest bid skipped waterproofing. You smell it the first summer.

A “bedroom” with a hopper window

Looks like a bedroom on the listing, fails at inspection or at the appraisal.

Carpet on a slab that still weeps

Cost to Renovate likes LVP in basements for a reason ($3 to $7 per square foot installed on their table). Carpet is comfortable and a problem when the water comes.

No path to the pipes

A hard-lid ceiling looks finished and makes the next leak a demolition. A drop ceiling is uglier and serviceable. Pick on purpose.

The bath that will not drain

Below the sewer without an ejector. That is a plumber, not a prettier toilet.

$18,000 drywall, or $34,000 with a drain

An 800-square-foot basement, open rec room, no bath. One bid is $18,000: framing, drywall, carpet, no moisture line, “permit by owner.” The other is $34,000: interior drain and sump, LVP, drop ceiling, heat run, building and electrical permits in the contractor’s name.

HomeGuide’s 800-square-foot open finish is $24,000 to $32,000. The cheap bid is under that because the water work and the permit are missing. Angi’s $32,000 average sits next to the complete bid.

If you later want a guest room, add Cost to Renovate’s $2,500 to $5,000 egress cut. If you want a shower, add their $6,000 to $12,000 full bath, not a vanity in the corner.

The cheap bid is not a deal on the same basement. It is drywall on a different scope.

Rec room, bedroom, or drywall over a damp wall?

What is the room for: TV, guests who sleep, a bath, or storage with nicer walls?

If anyone will sleep there, add an egress window line at Cost to Renovate’s $2,500 to $5,000, not Angi’s glass-only number.

Ask for moisture work in writing before framing. HomeGuide’s $1,900 to $6,300 waterproofing band is the check.

Price the bath as its own decision. A half bath and a full bath are not the same add.

Compare two bids that list rooms, moisture, HVAC, permits, and ceiling height. If one is half the price, it is usually half the scope.

You already paid for the hole in the ground. The bid is whether you are buying a rec room, a legal bedroom, or drywall over a damp wall.