"FFM non drip" is a galvanised pre painted profile sheet, heat coated on the reverse side with an unwoven fabric which regulates condensation. Humidity is absorbed by the fabric and evaporated later, when the temperature rises.

Applications

FFM non drip is ideal for single skin, insulation under rail and insulation over false ceiling constructions where condensation control is of prime importance.

FFM non drip does not exclude the natural ventilation of roof space.

Coating

Normally leathergrain embossed Plastisol 200 microns thick with an epoxy primer on the reverse.

The condensation regulating fabric

Composition: Unwoven polyester cellulose.
Colour: White
Thickness: 80 grammes per square meter covered

Corrosion Resistance

After 1000 hours in a salt spray, the adherence of the fabric to the steel sheet is identical to that before the test.

Four barriers separate the humid area from the steel:

• The zinc
• The chemical treatment
• The primer
• The adhesive

The corrosion resistance is therefore greatly improved.

Non Drip Processing

After numerous comparative tests, two components have been selected:

• A hard wearing tear resistant fabric
• An adhesive with excellent properties to guarantee its stability for bending, profiling, punching, and shearing processes under normal conditions.

Format

Non Drip is supplied in coil form with the overlap edge uncoated. This is to prevent water being drawn in to the lap by syphonic action.

Precautions

A varnish has to be site applied to the end of the overlap to prevent water ingress by syphonic action. Similarly this has to be applied to the gutter end of the sheet.

Alternatively a blow torch can be used as shown in the attached diagrams

FFM NON DRIP SHEETING INSTALLATION

To prevent damp from rising by capillary effect the sheets must be gently scorched using a hand held blow torch as indicated on the drawing.

A) The bottom of the incline and all overlapping parts. The entire width of the overhang must be scorched up to its fastening point (a width of at least 200mm).

B) Overhang. The minimum width to be scorched is indicated in the table below.

 

SLOPE P (Degrees)	Minimum width to be scorched in mm CLIMATIC AREAS
	NORMAL AREAS	COASTAL AREAS AND / OR AREAS EXPOSED TO STRONG WIND
Between 7º & 10º	300	N/A
Between 10º & 15º	200	300
Over 15º	150	200

The sheet must be laid flat to allow the scorching process to occur over the required full width. The scorching needs to be done carefully until the anti-con webbing starts to turn black.

Once cooled the black area should look and feel almost plastic.

If stored outdoors, non drip sheets should be protected from the elements.

Profiled sheets should not be allowed to slide on each other or on steelwork. If timber purlins are being used, the two surfaces should be separated by a suitable masking tape.