Wash Interior of Barn

I need advice on washing the inside of a barn. It’s a like-new barn with untreated lumber and extensive bird droppings. No mold, grease, or anything else. Customer just wants the bird poop gone. It has a concrete foundation with drainage hole. I don’t have hot water.

My primary questions are, 1) What detergent? 2) Is water damage a concern? 3) Would you take this job?

Any other considerations?

Surfactant, water, medium pressure and agitation. Good luck.


Is that the attic of the barn with osb flooring? If so do not wash it.


No way would i take that job. It would probably be cheaper to replace all the s#$t covered wood piece by piece.

Then spend the money you saved to train the birds to poop outside. Kidding.

Walk away, you’ll make more in the long run.

Raw untreated beams and just a couple of them? Why not just charge him to sand it off? Probably faster and less messy than using a pressure washer here.

Don’t use any water. Shop vac, scraper, sander, push broom if you really want to do it. If he’s worried about the staining on the osb you can always roll some paint over it. Oh yea, and one of those fake owls or a couple of rubber snakes scattered about when you’re done

Thank you all for the input. The bird droppings are much more extensive than the first picture shows, there’s spots everywhere. Another picture is below. Yes, that is OSB in the attic area, but there’s a hatch / ladder in the middle that would be easy to drain out of with tarps.

I have a try it at least once attitude so am going to put a hefty bid on it, along with a frank (and written) discussion about potential for water damage and also that I’m going to walk if it isn’t going well. He can take it or leave it. I’ll test out a few different surfactants and use brushes if necessary.

That attitude can get you in lots of trouble and lose you money.


I can think of no reason why one would entertain the idea of washing this.


Don’t forget to be honest with guy and tell him that the mess will be back in a matter of weeks, no matter what he does. All the owls, rubber snakes, etc in the world won’t stop the problem…The birds are scared of them for a week or two at most, and then they just ignore them (or use them as roosts)

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If you end up doing it rent some big air movers to dry the floors with and try to do it when the weather gets nicer. Maybe do it in sections one day a week or every couple days so you don’t get too much water build up and plug in a sump pump in the lowest area the water travels to. And definitely post how it went after!

Revival of an older thread…
I’ve been asked to clean the interior of a single story “barn” that has 3 stalls on each side for horses, emus, pigs, etc. The customer is wanting the cobwebs that are everywhere removed and not looking for the wood to look like new. Would anyone recommend an extremely light HW mix or something better? I know strong enough HW mix helps to “melt” away the cobwebs, but I haven’t attempted a weaker mix. There was not any animal fecal matter on the walls at the time I walked the property. I left my phone in the truck at the time due to a downpour of rain, but I’ve attached a few photos of a house from a previous cleaning that closely resembles the amount/makeup of cobwebs I’m targeting.

Weak hw mix will get rid of the spider webs


Depending on the type of spider surfactant may be enough. Some spiders weave much more resilient webs than others.

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