“FFM non-drip” Anti condensation roofing sheet 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.
FFM Non Drip is only available in our NWSSR32 Roof Profile.
FFM non-drip is the ideal solution for single skin insulation under rail and insulation over false ceiling constructions, where condensation control is of prime importance.
Mostly used in unheated and well ventilated buildings.
Normally leathergrain embossed Plastisol 200 microns thick with an epoxy primer on the reverse.
The condensation regulating fabric
Composition: Unwoven polyester cellulose.
Thickness: 80 grammes per square meter covered
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.
Non Drip is supplied in coil form with the overlap edge uncoated. This is to prevent water being drawn into the lap by syphonic action.
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
COASTAL AREAS AND / OR AREAS EXPOSED TO STRONG WIND
Between 7º & 10º
Between 10º & 15º
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.