This is caused by failure of the glazing method which must protect the unit seal from the ingress of water or moisture. All double glazing sealants used in the manufacture of double glazing units have a moisture vapour transmission rate when exposed to water or moisture, which will cause misting or breakdown eventually over a period of time. Where units are foreputtied, the putty must be painted and on to the glass to provide a seal to protect the putty from moisture ingress.
Foreputty should be left for 7 to 10 days before painting and within 28 days. Similarly when glazed with beads and non hardening compound, paint or protective coating should be applied over the bead and on to the glass. Where timber preservative has been used, Manufacturer’s instructions should be followed to prevent reaction with glazing compound.
It is recommended that timber windows should be painted every five years Inland areas and three years Coastal areas. However it is recommended that the paint protection of the glazing including the overlap on to the glass face, should be repainted every three years to maintain the required protection particularly with putty fronting as a minimum. However more frequent ‘spot painting’ may be necessary to maintain the required standard of protection.
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