FAQs on how to seal cracks in concrete floors, foundations, walls, or other masonry: this article how to seal and repair of cracks in poured concrete slabs, floors, or walls.

This article series lists all of the current methods used to seal control joints or cracks that occur in those building surfaces, giving the properties, general procedure, and pros and cons of each method.

Q&A on How to seal control joint & expansion joint cracks in concrete slabs

These questions and answers about approaches to sealing cracks or repairing cracked concrete floors, walls, slabs, foundations were posted originally at SEAL CRACKS in CONCRETE, HOW TO - be sure to see the options and repair products described there.

Watch out: before sealing concrete cracks like those at page top be sure that you've got a credible diagnosis of their cause.

See also FOUNDATION DAMAGE by MATERIAL or INCLUSIONS

[Click to enlarge any photo]

On 2019-08-28 by (mod) - will pressure valve stop concrete floor leaks?

Anon:

Pressure where and how?

The best way to stop leaks through concrete is to find and redirect the source of water under or outside the foundation walls or floor;

Other suggestions in a more complete guide are at https://inspectapedia.com/Wet_Basements/Basement_Waterproofing_Sealer.php BASEMENT WATERPROOFING

On 2019-08-28 by Anonymous

will pressure valve stop concrete floor leaks

On 2019-01-31 by (mod) - Should sealant be applied over a foundation crack prior to the polyurethane injection.

I can't affirm "should" or "have-to" seal a crack before "sealing" the crack - but I understand the reasoning;

My own preference is to apply the polyurethane foam first, so that by eye I can confirm that all of the crack was filled and sealed; I worry that if we try to inject foam behind a cement "crack sealant" we can't see if we've effectively filled the gap.

I prefer to tool or trim off any excess that oozes out of the crack where that's a concern.

Take a look at POLYURETHANE FOAM INJECTION CRACK REPAIRS https://inspectapedia.com/structure/Foundation_Crack_Repair_Foam_Injection.php

I have reviewed the product data and descriptions provided by several polyurethane crack sealing kit manufacturers and I did not find a requirement for nor even a description of a preliminary step involving applying some sort of crack surface cover-over before injecting the polyurethane sealant.

On 2019-01-30 by Joan

Should sealant be applied over a foundation crack prior to the polyurethane injection. This would keep the polyurethane in the crack and not let it leak out. One company does this.

On 2018-12-19 by Craig

Water is coming where the floor meets the foundation, right along the inside corner, slowly but then will pool water.
What can I do?

On 2018-12-04 by (mod) -

IPS

OPINION: First, your photo [shown just above] shows a history of moisture or water and some effloresence at a painted concrete block wall. There is no significant mold contamination visible in the photo.

Second, any household cleaner is fine for cleaning a moldy surface provided the surface is one that CAN be cleaned. Soft materials like drywall or insulation that are moldy need to be removed and discarded.

From what I read of its product description, Thieves® essential oil is a powerful combination of Clove, Lemon, Cinnamon, Eucalyptus Radiata, and Rosemary essential oils for an aromatic blend that fills any space with a rich, spicy aroma.

That product sells for about $45. U.S. for 15 ml of oil. It is intended for use as an aroma or on the skin when diluted in a ratio of 1:4 in olive oil. (1 drop Thieves oil to 4 drops olive oil)

Essential oils are in my view a completely inappropriate approach to removing an indoor mold contamination problem, and that's before considering that the square-foot cost would be about $50. / square foot to even apply oil to a surface (which doesn't sound like a smart idea) compared with about $0.01 or less for using a conventional cleaner.

You're spending 5,000 times as much per square foot if you take the application approach.

And that's before finding independent, scholarly research giving evidence that thieves essential oil is suitable or effective on foundation walls or as a "mold preventer".

If you want to add some essential oil to a household cleaner to make cleaning smell nice that's not likely to be harmful for most formulations, though I'm unclear how adding any oil product will improve the effectiveness of even the most basic cleaner such as Simple Green or borax or laundry soap and water.

In your photos the "gold brown stuff" is most likely also effloresence - see EFFLORESCENCE & BROWN DEPOSITS inspectapedia.com/Wet_Basements/Brown_Red_Effloresence.php

Essential oils smell great and appear, for some formulations, to have a range of uses.

For indoor mold contamination you need to remove the mold, fix the leaks that caused it, and dry out the area.

Essential oils including Thieves Oil might be helpful in cleaning small-area surfaces and in reducing some microbials, and has been patented for that use (Close 2009) but such oils are not an appropriate sole-solution mold remediation approach (you should remove the mold and fix its cause).

The patent disclosure I cite gives some background on mold remediation and presents essential oils as a low-cost mold remediation method (really? given the cost per ounce?) but does not include independent research supporting its claims.

It also cites using air sampling as a building mold screen, a fundamentally inaccurate result with very large orders of magnitude of variation in results depending on small changes in sampling conditions or methods.

Although all oils including essential oils are generally hydrophobic, I found no support for use of such oil as a foundation wall coating, nor for waterproofing a leaky basement wall, and that's before considering the 5000x cost of such an approach. But many such oils will, however, make the area smell nice.

On 2018-09-13 by IPS

Has anyone tried using the essential oil "thieves" for mold cleanup before or after sealing basement ground water cracks?

An environmental guy and his wife (well, they sell the stuff but their info seems interesting) seem to have done extensive result testing over the last 10 years using the original manufactured thieves blend oils and dispenser (not knock-offs)

and wondered if any comments for that? thanks (the attached photo is after I scrubbed some of the black off with a stiff brush and vinegar-water-dish soap but water actively seeping during rain storms,

and I suspect the gold-brown stuff is also mold?) Planning on trying some epoxy/poly caulk-like flexible something in the cracks to stop the water seepage. But was curious for any comments about the thieves oil blend stuff. thanks again

IMAGE LOST by older version of Comments code - now fixed. Please re-post the image if you can. Sorry. Mod.

On 2018-09-13 by IPS - ok so theives essential oil isn't suitable as a leaky basement foundation wall coating

thank you Moderator.

On 2018-09-13 by (mod) - You're spending 5,000 times as much per square foot

IPS

OPINION: First, your photo [shown just above] shows a history of moisture or water and some effloresence at a painted concrete block wall. There is no significant mold contamination visible in the photo.

Second, any household cleaner is fine for cleaning a moldy surface provided the surface is one that CAN be cleaned. Soft materials like drywall or insulation that are moldy need to be removed and discarded.

From what I read of its product description, Thieves® essential oil is a powerful combination of Clove, Lemon, Cinnamon, Eucalyptus Radiata, and Rosemary essential oils for an aromatic blend that fills any space with a rich, spicy aroma.

That product sells for about $45. U.S. for 15 ml of oil. It is intended for use as an aroma or on the skin when diluted in a ratio of 1:4 in olive oil. (1 drop Thieves oil to 4 drops olive oil)

Essential oils are in my view a completely inappropriate approach to removing an indoor mold contamination problem, and that's before considering that the square-foot cost would be about $50. / square foot to even apply oil to a surface (which doesn't sound like a smart idea) compared with about $0.01 or less for using a conventional cleaner.

You're spending 5,000 times as much per square foot if you take the application approach.

And that's before finding independent, scholarly research giving evidence that thieves essential oil is suitable or effective on foundation walls or as a "mold preventer".

If you want to add some essential oil to a household cleaner to make cleaning smell nice that's not likely to be harmful for most formulations, though I'm unclear how adding any oil product will improve the effectiveness of even the most basic cleaner such as Simple Green or borax or laundry soap and water.

In your photos the "gold brown stuff" is most likely also effloresence -

see EFFLORESCENCE & BROWN DEPOSITS

Essential oils smell great and appear, for some formulations, to have a range of uses.

For indoor mold contamination you need to remove the mold, fix the leaks that caused it, and dry out the area.

Essential oils including Thieves Oil might be helpful in cleaning small-area surfaces and in reducing some microbials, and has been patented for that use (Close 2009) but such oils are not an appropriate sole-solution mold remediation approach (you should remove the mold and fix its cause).

The patent disclosure I cite gives some background on mold remediation and presents essential oils as a low-cost mold remediation method (really? given the cost per ounce?) but does not include independent research supporting its claims.

To me it was also unclear if the reduction in airborne particles was due to more than simply the resistance offered by any oil coating against the release of airborne spores from mold fruiting bodies. The very limited research on this topic offers no study of controls using non-essential oils. Baby oil might have the same effect. (I am not recommending that approach.)

It also cites using air sampling as a building mold screen, a fundamentally inaccurate result with very large orders of magnitude of variation in results depending on small changes in sampling conditions or methods.

Although all oils including essential oils are generally hydrophobic, I found no support for use of such oil as a foundation wall coating, nor for waterproofing a leaky basement wall, and that's before considering the 5000x cost of such an approach. But many such oils will, however, make the area smell nice.

Research on Uses of & Effectiveness of Thieves Oil

• Chao, Sue C., D. Gary Young, and Craig J. Oberg. "Effect of a diffused essential oil blend on bacterial bioaerosols." Journal of essential oil research 10, no. 5 (1998): 517-523.
  
  Thieves, a commercial blend of five essential oils, was tested for its antibacterial activity against Micrococcus luteus, Pseudomonas aeruginosa and Staphylococcus aureus bioaerosols.
  
  An aerosol suspension of each bacterial culture was sprayed into a 0.4 m3 enclosed fume hood previously sterilized by ultraviolet light. Thieves essential oil blend was then diffused into the hood for a given time.
  
  Depositional sampling results showed a significant reduction (P<0.0001) in the aerosol-borne bacterial load after diffusion of the oil blend.
  
  Controls showed no inhibitory effect of oil that may have settled on the exposed plate surfaces during bacterial depositional sampling.
  
  Inhibition levels appear to be organism specific. There was an 82% reduction in M. luteus bioaerosol, a 96% reduction in the P. aeruginosa bioaerosol, and a 44% reduction in the S. aureus bioaerosol following 10 min of exposure. Results for the time exposure threshold of diffused oil showed that after only six min a 90% reduction in M. luteus viability occurred.
  
  Diffusion of the oil blend, Thieves, can significantly reduce the number of aerosol-borne bacteria and may have application in treating air for enclosed environments and preventing transmission of aerosol-borne bacterial pathogens.
• Close, Edward R., and Jacquelyn A. Close. "Method of mold remediation." U.S. Patent Application 11/849,039, filed March 5, 2009.
• Siegfried, Sara A., and Jennifer R. Schroeder. "Toxicity of thieves oils to mcf-7 and mda-mb-231 breast cancer cells." American Journal of Essential Oils and Natural Products 6, no. 1 (2018): 01-08.
  

On 2018-09-13 by IPS - using the essential oil "thieves" for mold cleanup

Has anyone tried using the essential oil "thieves" for mold cleanup before or after sealing basement ground water cracks?

An environmental guy and his wife (well, they sell the stuff but their info seems interesting) seem to have done extensive result testing over the last 10 years using the original manufactured thieves blend oils and dispenser (not knock-offs) and wondered if any comments for that?

thanks (the attached photo is after I scrubbed some of the black off with a stiff brush and vinegar-water-dish soap but water actively seeping during rain storms,

and I suspect the gold-brown stuff is also mold?) Planning on trying some epoxy/poly caulk-like flexible something in the cracks to stop the water seepage. But was curious for any comments about the thieves oil blend stuff. thanks again

On 2018-07-25 by (mod) - need a solution to basement cracks and leaks right away

David,

IN the article SEAL CRACKS in CONCRETE, HOW TO we suggest a range of concrete crack repair sealants and approaches.
Please take a look.

I can't offer more for a situation about which we have not a shred of information.


Doug:

Crumbling concrete blocks may be repairable if the block material itself is not defective. For example where blocks are damaged by frost or rain-splash we might wire-brush the loose material, paint with a bonding agent, then use mortar mix or another concrete patching compound like those discussed above.

But if the blocks were made poorly to start-with - that is without much portland cement - you may need to work carefully, one or two blocks at a time, removing and replacing individual bad ones.

If much of the wall is damaged your mason contractor may opine that it'll be less costly and more expensive to replace larger sections of the walls entirely.

Use the Add Image button and let me see the situation.

On 2018-07-25 by David

Need solution and any advice possuble

On 2018-07-09 by Doug

I am looking for a way to patch crumbling cement blocks on outside basement walls.

On 2018-05-17 by Angel Pabon

Seeking for a company in central Florida that repairs expansion joint cracks and remove existing epoxy and reseal with waterproof epoxy to stop water leaks. Does anyone know of a company that provide this type of service?

On 2018-04-27 by (mod) - sealing cuts in concrete to run conduit

[Click to enlarge image]

I can only speculate and do arm-waving since I don't have the full situation; always there's more to be seen on-site.

1. I would be very cautious about the muriatic acid cleaning, or better, don't put anything into the conduit cuts until after the muriatic acid treatment is completely over. Even then, keep it out of the trenches lest your wiring be later corroded and unsafe.

2. high portland cement or other additives can make a cap layer of concrete moisture resistant. There's little value in fooling around with vapor barrier in the bottom of your cuts as I suspect you can't really seal those anyhow (except maybe a pour-in sealant such as those pourable caulk/sealants used in radon mitigation.

On 2018-04-25 by Nathan S. Phillips

I am converting part of my garage to a livable workspace room, and am running electrical conduit in the concrete slab.

After placing the conduit, the entire slab for this room will receive additional concrete to level the sloped floor. In creating the trenches for the conduit, I have removed 1-2" wide sections of the slab approx. 4" deep in slab. In doing so, I've ripped up and destroyed the vapor barrier sheet between the slab and gravel in the trenches.

These narrow and deep (for fingers) trench sizes make it very hard to access the non-damaged part of vapor barrier under the slab next to trench in order to overlap and tape new vapor barrier sheeting to it.

So, I'm hoping to find some sort of thick liquid solution which I can pour, paint, etc. in the trench (which only has gravel underneath, so needs to be thick to not slip out of trench). I assume I will then need to apply new sheeting that would stick to this mastic.

To further add to the fun, the mason who will be leveling the slab will be using muriatic acid to clean and prepare the concrete for the added cement, so I need to either prevent the acid from getting into the trenches and destroying the sheeting and mastic, or better, fill trenches entirely with some cement prior to acid use. I've spent many hours researching this with little to show for it, so thanks for any input and advice you may share.

On 2018-04-05 by (mod) -

The following question and reply were received from an anonymous reader by private email 2018 04 05:

Reader question on sealing an Arizona garage slab:

We are purchasing a home, built on a slab in AZ, which shows evidence of moisture having built up and crumbled the concrete slab in the garage. The water/moisture is essentially coming from the landscaping. We imagined a trench along the concrete garage slab would be essential, but what "barrier" should be installed to prevent moisture from entering the garage?

Reply:

I would concentrate on keeping water away from the slab by sloped drainage and aim of any sprinklers. A trench along the slab acths as a catchment that risks actually sending more water under the slab.

I would defer patching the concrete until you know the water source has been solved.

Then you shouldn't need a barrier under the slab - and I note that adding one may be expensive as you'd have to drill and pump bentonite clay or a similar product under the entire slab surface.

On 2018-02-28 by (mod) - how do I rectify stains and patchy areas on off form concrete class 2 .

Solomon

take a look at CONCRETE STAINS: ID & REMOVAL at https://inspectapedia.com/exterior/Concrete_Stains.php

On 2018-02-28 by Solomon

Hello - how do I rectify stains and patchy areas on off form concrete class 2 .
I need the product to be the same colour as off form concrete class 2

On 2018-02-11 by (mod) -

Richars

You can build a masonry support wall or install steel I or U-channel beams against the existing foundation wall but really to stop future damage you'll need to remove the plants and roots causing the damage.

On 2018-02-11 by Richars

I have cracks on the wall caused by roots of 10 plants that go deep into the ground..any better and cheap way to secure the walls to prevent the walls from cracking

On 2018-02-02 by (mod) -

Nirran

I'm sorry but I probably don't have the correct understanding of how you are using the word soakaway.

Me that refers to an absorption system to dispose of septic or sewage or grey water effluent into the soil. I would not expect such a construction to be watertight and in fact I would not expect it to have a concrete floor.

So maybe you're asking me about something else. You could use the picture frame icon next to the comment button to attach a sketch or photos if that would help.

On 2018-02-01 1 by Niran

Pls,how do i seal my soakaway that is under construction? It was discovered that water is seeping out from its conrete floor and edges

On 2017-10-08 by (mod) - don't just seal the crack, check out first is it related to the foundation or not

Rahul Ekbote said:
Thanks a lot for this article and yes you are right don't just seal the crack, check out first is it related to the foundation or not, on similar note recently i have came across ... another article which is related to the same concept and it is useful too.
Thank You.

On 2016-12-22 by (mod) -

M

Please see our discussion of "slab jacking" in this article: https://inspectapedia.com/structure/Vertical_Foundation_Movement_Repair.php

On 2016-12-22 by M hayworth

Cracked in slab floor is unlevel, one side higher than other need to be leveled out help

On 2015-12-25 by (mod) -

I'd

1 check for causes of movement or settlement

2. Repair with refactory cement that will tolerate the heat

3 inspect the safety of the chimney and flue

On 2015-12-19 by John

Recently one of my clients noticed a crack in the back wall of her granite fireplace. We have sealed this crack once before with epoxy. The crack blew out again. This time the crack appears to be a little wider. Is epoxy the fix-all in this situation or are there other alternatives? Please advise. Thank you.

On 2015-10-07 by William

I am in a multi-story condo building (built in the early 80s) where the floors are of precast concrete units. There are a few units where the grout is falling out of the joints between the units into the living areas. What is the best way to seal these joints from the ceiling side?

On 2015-09-19 by Bruce

I have a commercial bldg. that has a 5 ft concrete wall that is below grade and block above, the water in coming in at the base where concrete wall and floor meet, this joint is in some places 1/2 in wide in other 1/8 to 1/4. I don't know if I should try and stop the water or just make provisions to allow it to come and drain. wall is about 500 ft long and sump pumps are already installed inside. humidity is a concern inside

On 2015-06-28 by Anonymous

Very informative. Now I know the steps for proper foundation crack sealing and how to go about my crack issue. I thank you for this very useful information.

On 2015-06-04 1 by Jerry Guillory

When our house was built in 1996, it came to the attention of the contractor by the bricklayer that the slab for the twelve-inch elevated porch was six inches too narrow, so the result was the pouring of a narrow slab the length of the porch upon which was laid a double brick wall against the concrete elevated slab.

Since there is no evidence of "tieing" the bricks to the elevated slab, contraction and expansion has caused a 1/16 inch crack to form for the length of the porch and about twelve inches from the edge of the porch. Any suggestions will be appreciated for possible repairs.

...

Continue reading at SHRINKAGE CRACK REPAIR or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Concrete Crack Diagnosis & Repair Articles

• CONCRETE COLD POUR JOINTS
• CONCRETE CORROSION DUE TO HYDROGEN SULFIDE
• CONCRETE DECK PIER PROCEDURE
• CONCRETE DIY SMALL JOB PROCEDURE
• CONCRETE DELIVERY & MIXING
• CONCRETE FOUNDATION, WALL, SLAB DEFECTS
• CONCRETE REINFORCEMENT, FIBER
• CONCRETE SHRINKAGE CRACKS
• CONCRETE SHRINKAGE CRACK REPAIR
• CONCRETE STAINS: ID & REMOVAL
• CONCRETE SLAB CRACK EVALUATION
• CONCRETE SLAB CRACK REPAIR
• CONTROL JOINT CRACKS in CONCRETE
• CRACK REPAIR STANDARDS for FLOORS
• POLYURETHANE FOAM INJECTION CRACK REPAIRS
• SEAL CONCRETE CRACKS, HOW TO
• SHRINKAGE CRACK REPAIR
• SLAB CRACK REPAIR STANDARDS
• VERTICAL FOUNDATION MOVEMENT REPAIR
• FOUNDATION DAMAGE by MATERIAL or INCLUSIONS

Suggested citation for this web page

SEAL CRACKS in CONCRETE, HOW TO FAQs at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to BUILDING STRUCTURES

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