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Question DetailsAsked on 8/14/2015

How must will it cost to put lime in a crawl space

There was sewage under house. Will lime disolve it?

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1 Answer


Lime will not "dissolve" it but it does soak up the moisture (which will actually delay its biodegradation, hence reducing the smell but making it last longer) - it is already "dissolved" - in an aqueous state. Treating it in place will not make it safe or prevent it from smelling in the long run though applying hydrated lime does initially kill smell and insect problems (kills flies and such directly if they get into the wet lime solution and also kills their eggs) - though also slows degradation, so subsequent rewetting (including from high air humidity) will restart the biodegradation and smell issue.

What you need to do is to physically remove the bulk of the sewage first - typically treating with diluted (25-50% strength) chlorine bleach or an antiseptic solution sprayed on first for worker safety and to kill the odor for a short time while they are working, then ventilating the area well before and during work, and it is then raked and shoveled and/or vacuumed up by a septic tank truck or wet/dry vac (depending on area being treated) - using a hose to spray the surface with limnited water to wet it so it can be removed. Generally about 1/2-1 inch of soil is removed in the process in crawl spaces/dirt floor basements, which gets the solids and the bulk of the fluid out in most cases. On concrete surfaces it is usually wetted and broomed and squeeged for vacuuming, then the surfaces hosed down with more vacuuming, finally sprayed and scrubbed with detergent and antiseptic solutions several times, then commonly treated with a anti-mold solution (mold killer or bleach), then anti-mold primer paint (for walls) like Kilz.

On dirt, the cleaned area is then sprayed or hand broadcast with a complete coating of powdered slaked or hydrated lime, also known as "S-lime" or "type S lime", chemical name calcium hydroxide. This comes as a loose dusty pure white "powdered sugar" consistency and color powder available at most building supply places (used as a component in many types of exterior mortar mixes), also generally available at feed stores because it is used to suppress smell and flies in outhouses and manure piles and runoff from manure and feedlot areas. Comes normally in 50 pound bags which, due to its fine powder form, are about the same size as 94 pound portland cement bags. It is NOT the same as the gray or tanish garden lime or garden dolostone powder which is just ground up limestone or dolomite, but which is pretty useless for this purpose - it will absorb moisture but does little or nothing to disinfect or stop odor or flies. Hydrated lime is somewhat corrosive when wet, both to metals and to the lungs when inhaled, and can irritate the mucous membranes in the eyes and nose and on other wet skin surfaces like hands and in concentrations can severly irritate skin (like if it gets through protective gear in boots or hands) in either dry or wet form, so full personal protective measures are needed when working with it.

Generally, while some plumbers will do a small cleanup and scatter a bit of lime after a sewer pipe break repair (up to a few buckets worth of sewage), for large areas usually a Biohazard Remediation or a Water and Smoke Damage company (your Search the List categories) company does the cleanup.

Cost vary widely by vendor and specific situation, but I would expect for an unconcreted crawl space with exposed soil (no insulation or vapor barrier) you are likely talking about $500-1500 cleanup for a normal say 500SF crawlspace or unfinished basement (assuming adequate working room - say about 3.5-4 feet or more) depending on how much sewage spilled and whether it filled the entire floor surface and it is got on foundation walls or underflooring too. For a concreted area you could be talking $500-1000 for bare concrete/block surfaces where water can be used freely; or a couple thousand commonly if it involves treating or tearing out damaged studwalls and drywall.

Unless very dilute sewage water only, any affected drywall or plaster or architectural finishes are not worth trying to save - demo them, but in many cases (if rot has not set in) the bare studwalls can be cleaned and treated acceptabl, if the insurance company and homeowner agree to that. It is common to totally gut a finished basement if the sewage was more than just a thin film deep over the floor (say if it built up 3-4 inches deep or more), or if it sat long enough to soak well in and start mold and rot in the walls.

I have seen a neighbor's house where a sewage leak of probably 100 gallons on dirt crawlspace was treated with lime but not cleaned up, and had new lime broadcast every 3-4 months but still pesistently smelled in damp or warm weather 10 years later - so trying to avoid the cleanup is not advised.

Plus if not properly cleaned up and treated, would have to be disclosed on a property disclosure form at time of sale - talk about a likely deal killer !

Answered 4 years ago by LCD

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