Blistering (Osmosis) of paint coatings applied to wall surfaces.
This this problem can be found on both interior and exterior wall surfaces is is associated with liquid water or water/moister water coming in contact contact within the building fabric.
Internally it can due to breakdown within the plumbing system. Externally by a fault within the build construction such as poor damp proofing, water from internal pipework wetting into the exterior building fabric.
Byway of capillary action water modules from wet or damp areas can move through a porous substrate (like brickwork), through any semi-permeable substrate i.e. render. The hydro moisture pressure builds, forming fluid-filled areas (water) under and within the underlying the porous substrate/s such as render. These wet areas can cause the underlying surface i.e. sand : cement mortar to become weak and crumble. This Hydro pressure can also cause the less porous with blisters forming on the exterior of the wall painted surface.
Exterior paint finishings although protecting the painted substrate from the ingress of moisture from external water i.e. rain /washing down they are not permeable to water are moisture vapour. Consequently surface blistering occurs and can due to the underlying weak substrate, render, can fail.
When problems of this nature are experienced to primary operations should be carried out: 1: gently remove the affected are exposing the underlying surface. 2: examine the reverse sire to the sample removed. 3: check with an approved moisture meter the moisture content of the area removed in relation the overall general area to establish the the
This can occur with any coating where moisture is trapped behind it, but it is a common issue with older properties lacking a functional DPC’s
At the same time, depending on the nature of construction capillary transfer of moisture vapourer can can take place and appear in locations away from its initial source.
See. Osmosis .Effloresces