How to Get Rid Of Old House Smells

Not All House Smells Are Equal

You walk into grandma’s house. Smells like mothballs and old carpet.

Annoying? Yes. Expensive to fix? No.

Now walk into a house that smells like mildew. That basement smell that hits you the second you open the door.

That one? Could be $15,000 in foundation waterproofing.

I’ve bought over 200 houses in Texas. About 50 had serious odor problems. Here’s what I learned: some smells mean open the windows and light a candle. Others mean call a structural engineer.

Let’s figure out which one you’re dealing with.

The 5 Smells That Mean Serious Money

These aren’t “spray some Febreze” problems. These are “get your checkbook” problems.

1. Persistent Musty Basement Smell

What it actually is: Water seeping through foundation. Creating perfect conditions for mold.

According to Bob Vila’s 2024 analysis, persistent musty odors that don’t go away with ventilation indicate ongoing moisture intrusion—not just humidity.

Real cost to fix: Foundation waterproofing runs $2,000-$15,000 depending on severity. Interior drain tile system? $8,000-$15,000. Exterior waterproofing? $10,000-$25,000.

We bought a house in Houston last year. Basement smelled musty. Homeowner thought it just needed dehumidifier. Turns out foundation had multiple cracks. Water came in every time it rained. Cost to fix? $18,000.

She sold to us instead. We bought as-is. She didn’t have to spend $18K.

2. Sewage or Rotten Egg Smell

This one’s bad. Really bad.

Could mean: Sewer line break. Dry P-trap. Cracked vent pipe. Dead animal in wall.

Sewer line replacement? $3,000-$25,000 depending on how much pipe needs replacing and whether it’s under concrete slab.

One Dallas house we bought had sewage smell in master bathroom. Previous owner tried everything. Air fresheners. Bleach. Vinegar. Nothing worked.

Problem? Cast iron sewer pipe from 1965 had corroded. Leaking under slab. Cost to reroute plumbing? $12,000.

3. Sweet, Sickly Smell (Like Rotting Wood)

This is hidden mold. Usually in walls or HVAC ducts.

Mold remediation costs according to HomeAdvisor’s 2024 data: $500-$6,000 for most homes. But if mold is throughout HVAC system? $3,000-$10,000 to clean or replace ductwork.

We bought house in Austin where previous owner couldn’t figure out smell. Turns out AC unit had been leaking for years. Mold throughout all ductwork. Total remediation cost: $14,000.

Owner sold to us for $185,000 instead of spending $14K she didn’t have.

4. Ammonia Smell

Rodents. Dead or alive. Usually in walls, attic, or crawlspace.

Rodent remediation costs: $300-$500 for trapping. But if they’ve been there a while? Insulation replacement ($1,500-$4,000), wire repair if they chewed electrical ($500-$3,000), sanitization ($500-$2,000).

Total bill for bad rodent infestation? $3,000-$8,000.

5. Chemical/Solvent Smell

Could be former meth lab. Or just old paint/chemicals stored improperly.

Meth contamination cleanup? $5,000-$25,000. Sometimes house is condemned and needs to be torn down.

If you smell chemicals and don’t know why, get the house tested before you do anything else.

The Cheap Fixes (Under $100)

Not every smell means structural disaster.

Some are actually easy fixes. Here’s what actually works.

Baking Soda (The $5 Solution)

Works for: Carpet odors. Pet smells. General staleness.

Doesn’t work for: Anything caused by moisture, mold, or structural issues.

How to use it: Sprinkle liberally on carpet. Let sit overnight. Vacuum thoroughly. Repeat if needed.

Cost: $5-$10 for enough baking soda to do whole house.

I use this in rental properties between tenants. Gets rid of dog smell about 70% of the time. The other 30%? Carpet needs replacing.

White Vinegar Bowls ($3 Solution)

Put bowls of white vinegar around house. Leave for 24-48 hours. Absorbs odors from air.

Works surprisingly well for smoke smell, cooking odors, general mustiness.

Doesn’t work for: Mold smell that keeps coming back. That’s moisture problem, not air problem.

Cross-Ventilation (Free)

Open all windows. Turn on fans. Push air OUT, don’t just circulate it.

Leave windows open for 6-8 hours. Ideally on dry, breezy day.

This works for houses that have been closed up for weeks or months. Like inherited property that’s been sitting empty.

But if smell comes back within days? You’ve got ongoing source. Ventilation won’t fix it.

Activated Charcoal Bags ($20-$30)

These actually work. Place them in closets, basements, problem rooms.

Absorb odors and moisture. Recharge them in sunlight every month.

Good for: Ongoing mild odor control. Not a replacement for fixing actual problem.

The Medium Fixes ($100-$500)

These cost more but actually solve problems instead of masking them.

Dehumidifier ($150-$300)

If your house smells musty because of humidity (not foundation leak), dehumidifier fixes it.

Keep humidity between 30-50%. Anything over 60% and you’re growing mold.

I keep dehumidifiers in all my rental properties in Houston. That humidity will destroy a house if you don’t control it.

But here’s the thing: dehumidifier only works if moisture is coming from humidity. If it’s coming from foundation leak? You’re just treating symptom, not cause.

Carpet Cleaning ($100-$300)

Rent commercial carpet cleaner from Home Depot. $40 for 24 hours.

Add enzymatic pet odor cleaner. About $30.

Spend a Saturday deep cleaning all carpets.

This works if carpet isn’t too far gone. But if smell doesn’t improve by 50% or more? Carpet needs replacing.

Pro tip: If you’re planning to sell soon and carpet smells bad, just replace it. Costs $2-$8 per square foot installed. Buyers will notice bad carpet immediately.

Ozone Generator ($80-$200)

These work for smoke smell. Really well.

But you CANNOT be in house while it’s running. Ozone is toxic to breathe.

Run it for 3-6 hours with house sealed up. Ventilate thoroughly before returning.

We used ozone generator on house where previous owner smoked inside for 30 years. Two treatments eliminated 80% of smell. Had to paint walls to get the rest.

HVAC Filter Replacement + Duct Cleaning ($100-$300 DIY, $300-$500 Pro)

Change your HVAC filter. Right now.

If it’s caked with dust and debris, that’s spreading smell throughout house every time AC runs.

If smell persists, ducts might need professional cleaning. Costs $300-$500 for average house.

One house we bought, previous owner thought she had mold problem. Spent $2,000 on mold remediation. Smell came back.

Actual problem? Dead rat in duct. Cost to find and remove? $180.

The Expensive Fixes ($1,000+)

Sometimes there’s no cheap fix.

Mold Remediation ($500-$6,000)

Small mold patch in bathroom? $500-$1,500 to remove and treat.

Mold throughout attic from roof leak? $3,000-$6,000.

Mold in HVAC ducts? $2,000-$10,000 to clean or replace ductwork.

According to Angi’s 2024 cost data, average mold remediation is $2,240. But severe cases easily hit $10,000+.

And here’s the kicker: if you don’t fix what CAUSED the mold (roof leak, foundation moisture, plumbing leak), it comes back.

Carpet Replacement ($2,000-$5,000)

Pet urine soaked into subfloor? Carpet cleaning won’t fix it.

Need to: Remove carpet. Seal subfloor with enzymatic sealer. Install new carpet and pad.

For 1,500 sq ft house: $3,000-$4,500 total.

We bought house where owner had 6 cats. No litter boxes. Cats used carpet as bathroom for years.

We had to: Remove carpet ($500), remove and replace damaged subfloor in two rooms ($1,200), seal remaining subfloor with odor blocker ($300), install new carpet ($3,800).

Total: $5,800.

Original owner didn’t have $5,800. She sold to us instead.

Foundation Waterproofing ($2,000-$15,000)

Persistent basement moisture causing that musty smell?

Interior waterproofing with sump pump: $2,000-$8,000.

Exterior waterproofing (excavate around foundation, apply membrane): $10,000-$25,000.

This isn’t optional if you want smell to actually go away. All the dehumidifiers in world won’t fix foundation leak.

Sewer Line Replacement ($3,000-$25,000)

If that sewage smell is from broken sewer line, you’re looking at serious money.

Spot repair: $500-$1,500.

Replace 50-100 feet of sewer line: $3,000-$8,000.

Replace line under slab or through yard with extensive landscaping? $10,000-$25,000.

How to Tell If It’s Worth Fixing

Do the math.

House worth $250,000. Needs $15,000 in repairs to fix smell (mold remediation, foundation waterproofing, new carpet).

After repairs, you could sell for $250,000. Minus 6% realtor commission ($15,000). Minus closing costs ($3,000). Minus the $15,000 you just spent.

Net: $217,000.

Or sell as-is to cash buyer for $200,000-$210,000. Close in 7 days. No repairs. No hassle.

Difference? Maybe $7,000-$17,000. But you save 3 months of mortgage payments, property taxes, insurance, utilities while house sits on market.

And you avoid risk of repairs costing more than estimated. Or buyer backing out after inspection.

Sometimes as-is sale makes more financial sense.

When Odors Mean Bigger Problems

Sometimes smell is just the warning sign.

Musty basement smell? Might also mean foundation movement, rotting floor joists, structural damage.

Sewage smell? Could indicate main sewer line collapse under entire house.

Mold smell? Often means roof leak you haven’t found yet. Or plumbing leak in walls.

We bought house in Plano last year. Owner complained about mildew smell in master bedroom. Thought it was just humidity.

When we inspected, found slow roof leak that had been going on for 2+ years. Attic insulation soaked. Drywall damaged. Mold in wall cavity.

Total fix: New roof ($8,500), mold remediation ($3,200), drywall replacement ($2,100), new insulation ($1,800).

Owner thought she was dealing with $200 dehumidifier problem. Actually was $15,600 problem.

She sold to us instead. We handled all of it.

Special Case: Hoarder Houses

These need their own category.

Hoarder house cleanup costs $1,000-$10,000+ depending on severity.

But cleanup is just first step. After junk is removed, you usually find:

– Carpet destroyed (needs replacement)

– Floors damaged from urine/spills

– Walls need repainting or drywall replacement

– HVAC system contaminated

– Pest infestations

– Plumbing issues from overloaded drains

Total cost to make hoarder house sellable? $15,000-$50,000.

We buy 3-5 hoarder houses per year. Always as-is. Family members don’t have money or emotional capacity to deal with cleanup and repairs.

We handle everything. They get cash and walk away.

Bottom Line: When to DIY vs. When to Call Us

Try DIY if:

– Smell is mild and recent (house was just closed up)

– You can identify obvious source (spilled milk, forgot to take out trash)

– Ventilation and cleaning make noticeable improvement

– Total cost under $500

Skip DIY and call professionals if:

– Smell persists after ventilation and cleaning

– You can’t identify source

– Smell is getting worse

– You see visible mold, water damage, or structural issues

– Estimated repairs exceed $5,000

– You’re planning to sell anyway

Consider selling as-is if:

– Repair estimates exceed $10,000

– You don’t have cash for repairs

– You don’t want to manage contractors for months

– House has multiple issues beyond just smell

– You need to sell quickly