Subfloor Preparation Subfloor Preparation and Moisture Mitigationand Moisture Mitigation

““an ounce of prevention is worth a an ounce of prevention is worth a pound of cure”pound of cure”

Benjamin FranklinBenjamin Franklin

OutlineOutline

Concrete Slab BasicsConcrete Slab Basics Moisture Sources and Testing MethodologiesMoisture Sources and Testing Methodologies Repairing Defects in Concrete SurfacesRepairing Defects in Concrete Surfaces Crack Repair TreatmentsCrack Repair Treatments Treatments for Moisture Vapor Emission Treatments for Moisture Vapor Emission

Concrete BasicsConcrete Basics

CementCement Supplementary Supplementary

MaterialsMaterials AggregatesAggregates WaterWater

Moisture SourcesMoisture Sources

Water of HydrationWater of Hydration Water required to complete chemical reactionWater required to complete chemical reaction

• Typically considered ~25% of cement by weightTypically considered ~25% of cement by weight

Water of ConvenienceWater of Convenience Water used for ease of workability and placementWater used for ease of workability and placement

• Usually another 25% to 40% of cement by weightUsually another 25% to 40% of cement by weight

Moisture Vapor Transmission (MVT)Moisture Vapor Transmission (MVT) Water of convenience evaporatingWater of convenience evaporating

• 4” slab poured at .50 W/C evaporates >½ gallon per sq ft.4” slab poured at .50 W/C evaporates >½ gallon per sq ft.

Water coming up through the concrete from under slabWater coming up through the concrete from under slab

Water in the SlabWater in the Slab

Free waterFree water This water is found within This water is found within

the capillaries of the slab the capillaries of the slab and will begin to evaporate and will begin to evaporate if given the correct if given the correct conditions.conditions.

Bound waterBound water This is the water that is This is the water that is

permanently bound as an permanently bound as an integral part of the concrete integral part of the concrete slab.slab.

Concrete Curing/DryingConcrete Curing/Drying

All concrete requires All concrete requires time to “dry”. time to “dry”. 4” concrete slab with a 4” concrete slab with a

0.5 w/c ratio over an 0.5 w/c ratio over an impermeable moisture impermeable moisture barrier will take barrier will take approximately 92 days approximately 92 days to get to a suitable to get to a suitable level for wood floor level for wood floor installation installation

Reference: “Are your slabs dry enough for floor coverings?” By Bruce Suprenant and Ward R. Malisch, Copyright 1998

Drying of ConcreteDrying of Concrete

Thickness of concrete Thickness of concrete slab also impacts slab also impacts drying timedrying time

Open or Closed SystemOpen or Closed System

Open system: Slab in contact with earthOpen system: Slab in contact with earth Greater opportunity for introduction of water post construction.Greater opportunity for introduction of water post construction. It is prudent to consider any slab of age to be an open system. It is prudent to consider any slab of age to be an open system.

(compromised closed system design)(compromised closed system design)

Closed System: Slab separated with a vapor “barrier” Closed System: Slab separated with a vapor “barrier” Recommended within ASTM F710Recommended within ASTM F710 Greater protection from introduction of water post construction, Greater protection from introduction of water post construction,

but not bullet proof and often times not constructed according to but not bullet proof and often times not constructed according to ASTM F710.ASTM F710.

Basic Concrete Slab ConstructionBasic Concrete Slab Construction

Site evaluationSite evaluation Compressed soilCompressed soil Large aggregate (capillary Large aggregate (capillary

break)break) Smaller aggregateSmaller aggregate

Moisture barrier Moisture barrier specificationsspecifications

0.010” thick reinforced film0.010” thick reinforced film

Exterior Drainage and Exterior Drainage and Landscaping concernsLandscaping concerns

Closed System Closed System

A vapor barrier’s purpose from a A vapor barrier’s purpose from a construction point of view differs construction point of view differs from the floor covering industry’s from the floor covering industry’s and building occupier’s and building occupier’s perspective. Vapor barriers at the perspective. Vapor barriers at the time of slab pour are intended to time of slab pour are intended to trap the necessary water required trap the necessary water required for proper curing. Not an for proper curing. Not an adequate barrier for long term adequate barrier for long term protection from moisture protection from moisture migration. migration.

How Moisture Moves Through a How Moisture Moves Through a SlabSlab

On grade concreteOn grade concrete Capillary & MVTCapillary & MVT

Below grade concreteBelow grade concrete Capillary, MVT & Capillary, MVT &

Hydrostatic PressureHydrostatic Pressure

Moisture Testing per ASTMMoisture Testing per ASTM

Ravages of MoistureRavages of Moisture

Amount of Moisture Extracted MVE of 20 lbs./1,000 sq. ft. (9,07 kg per 92,9 m)/ 24 hours

7 Days of Extracted Moisture

20lb MVER

Roughly 16 gallons of water over a 7 day period over an area approximately 31’x31’

Flooring Moisture IssuesFlooring Moisture Issues

Solutions for Moisture ControlSolutions for Moisture Control

Silicate Penetrating SealersSilicate Penetrating Sealers Topical SealersTopical Sealers Epoxy CoatingsEpoxy Coatings Cementitious OverlayCementitious Overlay Single system approach (adhesive acts as Single system approach (adhesive acts as

bonding agent and moisture control solution)bonding agent and moisture control solution)

Penetrating SealersPenetrating Sealers

Penetrating type reactive sealers are liquid applied treatments that Penetrating type reactive sealers are liquid applied treatments that chemically react with the concrete reducing the MVER.chemically react with the concrete reducing the MVER.

There are also products that are incorporated into the product at the There are also products that are incorporated into the product at the time of pour. (mixed in the truck)time of pour. (mixed in the truck)

These may be silicate in nature (sodium, lithium, or potassium)These may be silicate in nature (sodium, lithium, or potassium) Some concrete mixtures will affect the efficacy of these types of Some concrete mixtures will affect the efficacy of these types of

sealants in relation to moisture/ph suppression and bonding sealants in relation to moisture/ph suppression and bonding compatibility with flooring adhesives. compatibility with flooring adhesives.

Silicate type treatments are considered by some with much less Silicate type treatments are considered by some with much less confidence than other topically applied productsconfidence than other topically applied products

Top Coat SealersTop Coat Sealers

Typically used for lower MVER/PH Typically used for lower MVER/PH conditions (approx. 8 lbs)conditions (approx. 8 lbs)

May not require slab surface May not require slab surface preparation depending upon preparation depending upon surface condition of the slab surface condition of the slab

Not typically recommended for Not typically recommended for open slab systems. open slab systems.

May not be recommended for May not be recommended for below grade slabs.below grade slabs.

Creates “non-porous” substrateCreates “non-porous” substrate

Epoxy CoatingsEpoxy Coatings

There are single and multiple coat There are single and multiple coat systems available.systems available.

Designed for very high moisture/ph Designed for very high moisture/ph conditionsconditions

Designed to reduce MVER to a Designed to reduce MVER to a tolerable level at the bond line.tolerable level at the bond line.

Isolates PH from flooring system.Isolates PH from flooring system. Typical that slab must be abraded Typical that slab must be abraded

through grinding or shot blasting.through grinding or shot blasting. Typical that a cementitious over lay is Typical that a cementitious over lay is

required due to type of adhesive used required due to type of adhesive used for the floor covering and/or repair for the floor covering and/or repair trenching caused by concrete surface trenching caused by concrete surface preparation.preparation.

May include a sand broadcastMay include a sand broadcast

Concrete Profiles for Epoxy Concrete Profiles for Epoxy MembranesMembranes

Dual Function Adhesive SystemsDual Function Adhesive Systems

New adhesive products designed New adhesive products designed to seal the slab and act as a to seal the slab and act as a bonding agent in one step.bonding agent in one step.

Water based acrylic adhesiveWater based acrylic adhesive Moisture cure urethane adhesiveMoisture cure urethane adhesive

Typically designed for a maximum Typically designed for a maximum of 15lbs MVER and 90% RHof 15lbs MVER and 90% RH

May not be designed for certain May not be designed for certain types of floor coveringtypes of floor covering

May or may not be recommended May or may not be recommended for open slab systems or slabs for open slab systems or slabs with hydrostatic pressure.with hydrostatic pressure.

Dense Cementitious OverlayDense Cementitious Overlay

Usually requires preparation of the slab’s surfaceUsually requires preparation of the slab’s surface Primer is applied prior to top coatPrimer is applied prior to top coat Highly densified cementitious layer is poured (may be Highly densified cementitious layer is poured (may be

self-leveling)self-leveling) Floor patching as needed to bring to floor coverings Floor patching as needed to bring to floor coverings

required levelness benchmark.required levelness benchmark. Isolates slab from floor covering system.Isolates slab from floor covering system.

Slip Sheet MembranesSlip Sheet Membranes

““Free floats” accommodating Free floats” accommodating minor cracks and joints.minor cracks and joints.

Shot blasting or grinding is not Shot blasting or grinding is not required.required.

Not necessarily compatible Not necessarily compatible with all flooring systems.with all flooring systems.

Effectively isolates floor Effectively isolates floor covering away from the slab covering away from the slab alleviating build up of vapor alleviating build up of vapor pressure. (vapor moves pressure. (vapor moves laterally)laterally)

PH resistantPH resistant

Decisions Drivers and Pitfalls for Decisions Drivers and Pitfalls for Moisture Solution SelectionMoisture Solution Selection

Amount of remediation required (MVER and RH Levels)Amount of remediation required (MVER and RH Levels) Available funds (Moisture Issues not typically expected) Available funds (Moisture Issues not typically expected) Incorrect system chosen for existing conditions / Lack of investigation.Incorrect system chosen for existing conditions / Lack of investigation. Incomplete system that does not include accommodations for cracks or Incomplete system that does not include accommodations for cracks or

joints.joints. System requires “certification” prior to purchase and application / WarrantiesSystem requires “certification” prior to purchase and application / Warranties Liability/Support if failure occursLiability/Support if failure occurs Incorrect application or slab preparationIncorrect application or slab preparation

REPAIRING DEFECTS IN REPAIRING DEFECTS IN CONCRETE SURFACESCONCRETE SURFACES

Minor Defect RepairsMinor Defect Repairs

Cement Based with Liquid Cement Based with Liquid Polymer AdditivesPolymer Additives

Dry Polymer Modified Cement Dry Polymer Modified Cement basedbased

Dry Polymer Modified Gypsum Dry Polymer Modified Gypsum based (residential and light based (residential and light commercial use)commercial use)

High hydrating, polymer and High hydrating, polymer and fiber reinforced cement based fiber reinforced cement based underlayments (skim coats)underlayments (skim coats)

Typical Usages: From Feather Typical Usages: From Feather egde to 1-1.5” Thickness in egde to 1-1.5” Thickness in single applicationsingle application

Use “exterior rated” patching compounds on slabs with moisture issues.

Large Area RepairsLarge Area Repairs

Self Leveling Self Leveling UnderlaymentsUnderlayments

PrepPrep• Make sure the substrate has Make sure the substrate has

the proper CSP or profile to the proper CSP or profile to receive the levelerreceive the leveler

PrimePrime• Select the right primer for the Select the right primer for the

substratesubstrate PourPour

• Follow all instructions on the Follow all instructions on the package package

Wait 3 days for floor covering Wait 3 days for floor covering installationinstallation

Deep Fill RepairsDeep Fill Repairs

ScreedsScreeds Typical fills up to 4” Typical fills up to 4”

thickthick Cure time relatively Cure time relatively

quick but reset the quick but reset the clock in terms of clock in terms of flooring acceptance as flooring acceptance as much as 30 daysmuch as 30 days

Concrete Profiles for Self Leveling Concrete Profiles for Self Leveling UnderlaymentsUnderlayments

Crack RepairCrack Repair

Mechanically prepare control and Mechanically prepare control and construction/expansion joints with a construction/expansion joints with a diamond crack-chasing/concrete-diamond crack-chasing/concrete-cutting blade. cutting blade.

Overcut the joint width to obtain a Overcut the joint width to obtain a sound, clean edge. sound, clean edge.

Clean cracks or joints with oil free Clean cracks or joints with oil free compressed air and/or vacuum with a compressed air and/or vacuum with a dustless collection system to dustless collection system to completely remove contaminants completely remove contaminants

An Engineer or Consultant determines if a crack is ‘dormant’ or ‘active’ and

which product to use

He who lives upon hope, dies fasting.He who lives upon hope, dies fasting. Benjamin FranklinBenjamin Franklin