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THE EFFECTIVE USE OF SURFACE DAMP PROOF …

Resin Flooring AssociationTHE EFFECTIVE USE OFSURFACE DAMP PROOF MEMBRANESFeRFA Guidance Note: No. 5 SURFACE DPM CONTROLS MOISTURE VAPOUR RELEASE FROM CONCRETE TO PREVENT BLISTERING AND DEBONDING OF THE RESIN FLOORING RESIN FLOORING PRIMER LEVELLING SCREED SURFACE DPM CONCRETE CONVENTIONAL DPM HARDCORE FAST TRACK CONSTRUCTION IN THE PRESENCE OF A CONVENTIONAL DPM IN THE ABSENCE OF A CONVENTIONAL DPM a small number of instances it is found that floorsin old buildings remain apparently unaffected bymoisture.

www.ferfa.org.uk GUIDANCE The Resin Flooring Association THE EFFECTIVE USE OF SURFACE DAMP PROOF MEMBRANES FeRFA Guidance Note: No. 5 SURFACE DPM CONTROLS MOISTURE VAPOUR RELEASE FROM CONCRETE

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Transcription of THE EFFECTIVE USE OF SURFACE DAMP PROOF …

1 Resin Flooring AssociationTHE EFFECTIVE USE OFSURFACE DAMP PROOF MEMBRANESFeRFA Guidance Note: No. 5 SURFACE DPM CONTROLS MOISTURE VAPOUR RELEASE FROM CONCRETE TO PREVENT BLISTERING AND DEBONDING OF THE RESIN FLOORING RESIN FLOORING PRIMER LEVELLING SCREED SURFACE DPM CONCRETE CONVENTIONAL DPM HARDCORE FAST TRACK CONSTRUCTION IN THE PRESENCE OF A CONVENTIONAL DPM IN THE ABSENCE OF A CONVENTIONAL DPM a small number of instances it is found that floorsin old buildings remain apparently unaffected bymoisture.

2 But as soon as resin flooring is installedthe situation quickly deteriorates! Many of theseold concrete floors may well have had sealers applied, but because they were usually vapourpermeable, the level or effects of moisture were notevident. The application of most types of resinflooring effectively creates a seal to the already trapped in the concrete, or risingfrom below, can then lead to problems of blisteringor detachment, although the onset of the problemsmight not occur difficulties of dealing with the refurbishment ofold concrete floors or the installation of new floorswhere the programme does not allow sufficienttime for the concrete base to dry out.

3 Have led to arequirement for the development of newtechnology resulting in the introduction of liquidapplied SURFACE damp PROOF membranes (DPMs).What is a SURFACE Damp ProofMembraneBy definition it is a liquid system applied evenly tothe SURFACE of a concrete base, that adheresstrongly to it even if the base contains a high level ofmoisture, and then sets to form a layer of controlledpermeability to moisture vapour (normally less than4g/sqm / 24 hrs). The set membrane must thenallow other flooring layers to be appliedOne of the oldest established SURFACE DPMs ismastic asphalt, which is usually laid on a fibreglassquilt or other isolating membrane .

4 However asphaltfloors are often susceptible to long termembrittlement and cracking. In addition heavypoint loadings or repeated trafficking can causeindentations and ruts to form, and there may behealth and safety issues associated with itsapplication and recently, advances in epoxy resin technologyenabled the formulation of coatings that aretolerant of high levels of moisture in the base towhich they are to be applied, and which allowtrapped moisture to permeate in a controlled waywithout causing distress to the membrane or to theapplied floor SURFACE DPMs are based on Epoxy resintechnology due to its excellent adhesive propertiesalthough there is no inherent reason why other resintypes might be suitable.

5 The membranes aregenerally applied by trowel, brush, roller orsqueegee in two or more coats, depending on thespecification in relation to the level of moisture inthe base concrete. Each coat is preferably appliedat right angles to the previous coat in order toensure a complete and uniform do SURFACE Membranes Work?A SURFACE membrane is effectively a vapour releasecontrol valve and works on the principle that allresin finishes, in the same way as polyethylene film,are vapour permeable to some degree. In selectinga SURFACE membrane for a particular situation, theproperties of all of the subsequent resin layersmust be considered to ensure that there isadequate control of Moisture Vapour transmissionto prevent failure.

6 A coarse quartz-filled screed forexample; is likely to have a much higher vapourtransmission rate than a 3-4mm self is important to note that the performance ofthese products depends on their ability to adhere tothe substrate and restrict the passage of moisturevapour to a level which does not adversely affectthe floor finishes. It is critical, therefore, that thecoating is applied uniformly across the wholesurface, is free from holes and applied at thecorrect thickness. Failure to observe thesebasic requirements can result in an increase in themoisture vapour transmission rate and subsequentfailure of the flooring manufacturers offer what are called singlecoat membranes but their claims need to be fullyevaluated, particularly with respect to limitations,warranties.

7 SURFACE DPMs require a primer and/oraggregate blinding prior to the application ofpumped cementitious underlayment systems inorder to create an adequate mechanical manufacturers supply products that formsurface membranes but it is essential to recognisethe subtle difference between a SURFACE DPM and aMoisture Vapour Suppressant:A SURFACE Damp PROOF membrane is designedto suppress excess residual/ construction moisturein new screeds and concrete and to protect againstrising moisture from the Vapour Suppressants will not protectagainst continued rising moisture from the are designed to suppress excess residual/construction moisture in existing buildingsIn the absence of positive evidence to the contraryit is wise to assume that any pre 1970 buildings areunlikely to have an EFFECTIVE DPM incorporatedinto their construction.

8 It was not until that timethat the necessity of a DPM was more in the Building Regulations. Sincethen, polyethylene or bituminous sheet membranesbecame more commonly used but experience hasshown that these cannot always be relied on. Alltoo often the joints were not correctly taped andwelted and these membranes were frequentlypunctured by steel reinforcement and site trafficbefore the concrete was even poured. A smallfailure in a sheet membrane can have catastrophiceffects on floor finishes applied directly in new constructionSome modern warehouse buildings are still builtwithout an EFFECTIVE DPM on the assumption thatthe concrete floors will remain uncovered.

9 In manycases this is a short-sighted policy. If there issubsequently a change of use, eg from storage toprocess area, or ill-considered renovations ( conversions and decorative coatingapplication) then damp problems can soon arisewith major disruption to normal operations in increased demand for denser, higherperformance and lower maintenance resin flooringsystems has increased the number of floor failureswhich are due to excess moisture in the a sandwich membrane has not beenincluded under the screed or slab, or where theintegrity of the DPM is questionable, a SURFACE DPMwill be Membranes - Do We NeedThem?

10 IN NEW BUILDINGS, WE SHOULD NOT!The Specifier has designed the building andselected the floor finish to meet usage andperformance Builder constructs the building to thisspecification and applies a work schedule whichgives the specialist contractor all the help requiredwithin the British Standards and BuildingRegulations to allow the quick and EFFECTIVE layingof the floor British Standards Codes of Practicerecommend that the building is protected againstrising moisture by incorporating a sandwich DPM, sothat the selected floor finish can be laid safely in new buildings a SURFACE membrane will not beneeded is an EFFECTIVE and approved damp proofmembrane (to British Standards).


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