TL;DR
A dog house that smells musty has a moisture problem, not a dirt problem. Strip the bedding, scrub the inside with soap and water, rinse it thoroughly, and then leave it open until it is bone dry. If the smell comes back within a month, the fix is drainage, airflow, or a leaking roof rather than more scrubbing.
Why dog houses go bad
A dog house is a small, enclosed, poorly ventilated box with a warm animal in it. That combination produces condensation, and condensation is what feeds mildew.
Three things make it worse. A roof or seam that leaks lets rain in directly. A floor sitting flat on wet ground wicks moisture up from below. And bedding that never fully dries keeps the interior humid even in good weather.
In a wet climate like the Willamette Valley, where damp weather runs for months, this is the normal state of an unmaintained dog house rather than the exception.
Cleaning fixes the current smell. Fixing the moisture is what stops it returning.
Never bring bleach and ammonia together here
Dog urine contains ammonia. Chlorine bleach must never contact ammonia, because the reaction releases chloramine gas, and inside a small enclosed structure that is a genuinely dangerous place for it to happen.
That means bleach on a soiled dog house floor is a bad idea even with no second product involved. It also rules out bleach with vinegar or any acidic cleaner, which releases chlorine gas.
Soap and water plus a thorough rinse does the job. For odor that soap does not resolve, use an enzyme-based pet cleaner, which breaks down the compounds causing the smell and carries no mixing risk.
If you decide a stronger step is needed after a parasite or an illness, ask your veterinarian what product they recommend and how long it needs to stay wet, then rinse it away completely and dry the structure fully before your dog returns.
Source: Centers for Disease Control and Prevention household chemical safety guidance
How do you clean a dog house?
Move your dog somewhere safe, remove all bedding, and sweep or scrape out the loose debris. Scrub the floor, walls, and roof interior with warm soapy water and a stiff brush, rinse everything thoroughly with plain water, then leave the house open in the air until it is completely dry.
The step-by-step routine
1. Empty it completely. Bedding, toys, bowls, and anything stored inside.
2. Sweep and scrape. Dry debris, hair, and hardened material come out with a stiff brush and a plastic scraper. Bag it.
3. Take the roof off if it lifts. Many dog houses have a removable or hinged roof, and cleaning one with the roof on is twice the work and half the result.
4. Scrub with warm soapy water. A stiff brush over the floor, the walls, the ceiling, and the door frame. The floor corners and the joint where the floor meets the wall are where everything collects.
5. Do the outside too. The roof, especially, since debris and algae hold moisture against the structure.
6. Rinse thoroughly. A hose is fine on plastic and sealed wood. Rinse until no suds appear anywhere.
7. Tip it up to drain. Stand the house on its side or its back so water runs out rather than pooling in the floor corners.
8. Dry it completely. Leave it open in the air, ideally in sun and wind, for at least a day. Two days for wood in damp weather. Do not put bedding back into a damp house.
Wood, plastic and the mildew smell
Plastic and resin houses. Easy. Soap, water, hose, drain, dry. Nonporous surfaces do not hold odor, so a persistent smell in a plastic house means the bedding or the ground underneath.
Wooden houses. Wood absorbs, so scrub along the grain and avoid soaking. Let it dry hard, then check for soft spots, dark staining, and lifting seams. Reseal exterior wood periodically with a pet-safe finish, applied with the dog away and fully cured before the dog returns.
Mildew smell in wood. Once the wood is scrubbed, rinsed and fully dried, most of it goes. What remains usually means the wood is damp inside, which is a drying and drainage problem.
If you find widespread growth on structural surfaces, that is a remediation question rather than a cleaning one. Mold remediation is a separate trade, and repeated scrubbing of a chronically wet structure does not resolve it.
Fixing the moisture, which is the actual repair
Cleaning without this step means doing it again in a month.
Get the house off the ground. Feet, blocks, a pallet, or a raised platform, so air moves underneath and moisture cannot wick up.
Check the roof and the seams. Look for gaps at the roof joint, missing or cracked shingles, and any spot where daylight shows through. Reseal or repair.
Angle the floor slightly. Even a small tilt sends water out the door rather than into the back corner.
Add ventilation. A vent near the roof line lets humid air escape without creating a draft on the dog.
Reposition it. Out of a low spot where water collects, out of a spot that never gets sun, and with the door away from the prevailing wind.
Watch the bedding. Straw and hay drain and dry, though they need changing regularly. Blankets hold water and mildew fast. Raised beds keep a dog off a cold wet floor entirely.
Bedding, bowls and the area around it
Wash fabric bedding on a hot cycle if the label allows, with unscented detergent and no fabric softener, and dry it completely. Replace straw rather than washing it.
Wash outdoor bowls daily, since food and water outside attract insects and wildlife. Pick up waste from the area regularly, because that is the real source of most outdoor pet odor.
Trays and pans in a kennel run have their own routine, covered in how to clean kennel floor pans and trays, and a fabric playpen used outdoors follows the method in how to clean a pet playpen.
For the rest of the kit, our guide to cleaning pet bowls, bedding, toys and gear keeps the same clean-then-dry-completely discipline.
How often should you clean a dog house?
Sweep it and shake out the bedding weekly, wash the bedding every one to two weeks, and do a full wash-and-dry of the house monthly during heavy use.
Twice a year, do the works: strip it, scrub it, dry it, check the roof and the seams, and reseal wood if needed. The natural times are the start and the end of the wet season.
A word on outdoor living generally. A dog house is shelter, not a substitute for warmth or company, and extreme heat or cold is a real risk for a dog kept outside. Your veterinarian is the right person to advise on what your specific dog can safely tolerate.
FAQ
How do you get the mildew smell out of a dog house?
Strip it, scrub the interior with warm soapy water and a stiff brush, rinse thoroughly, and dry it completely in air and sun for a day or two. If the smell returns within a month, the cause is moisture: raise the house off the ground, fix leaks, and add ventilation.
Can you use bleach to clean a dog house?
It is a poor choice. Dog urine contains ammonia, and bleach plus ammonia releases chloramine gas inside a small enclosed structure. Use soap and water plus a thorough rinse, and an enzyme-based pet cleaner for stubborn odor. Ask your vet if a stronger step seems necessary.
How often should you clean an outdoor dog house?
Sweep it and shake out the bedding weekly, wash the bedding every one to two weeks, and do a full wash and dry of the house monthly during heavy use. Do a complete strip, scrub, and structural check twice a year, at the start and end of the wet season.
What is the best bedding for an outdoor dog house?
Straw drains and dries well and can be replaced cheaply, though it needs changing regularly. Blankets hold water and grow mildew quickly in damp weather. A raised bed keeps a dog off a cold wet floor entirely, which does more for comfort than extra bedding does.
How do you stop a dog house getting damp inside?
Raise it off the ground on feet or a pallet so air moves underneath, seal any roof or seam leaks, tilt the floor slightly toward the door, and add a vent near the roof line. Reposition it out of low ground and somewhere it gets some sun.
Can you pressure wash a dog house?
Only on plastic or resin houses, and even then keep the pressure moderate. High pressure on wood raises the grain, drives water deep into the timber, and strips protective finish, which makes the damp problem worse. A stiff brush and soapy water works better on wood.
Outdoor pet areas are one small piece of a much larger job. Every home is different, so the real number depends on size, condition, and what you want covered. Get a quote or read more about house cleaning services.