Efflorescence Under a Suspended Floor: What the Borescope Revealed

This second borescope image, taken during the same sub-floor inspection, shows the extent of salt bloom more clearly. The entire visible surface is coated in white crystalline efflorescence, with darker damp patches between the drier crystal formations. That combination is a textbook picture of a void that has been repeatedly wetting and drying over a long period.

Reading the image properly

Efflorescence on its own tells us that water has moved through and evaporated from the material. What matters is the scale and distribution. A light dusting in one spot is often historic and inactive. A dense, continuous layer across a large area - as seen here - indicates an active or recently active moisture pathway that has never been properly addressed.

What we look at next

Once the void condition is documented, the investigation moves outside and around the property. We check external ground levels against the internal oversite level, the condition and position of the damp proof course, air brick provision and whether any are blocked, downpipe and gully condition, and any nearby paths, driveways or planters that might be trapping water against the wall.

Inside, we assess whether the moisture is affecting rooms above - cold floors, low-level mould, condensation on skirtings, or musty odours in cupboards and understair spaces are all secondary symptoms of a wet void.

Our recommendations

Improve sub-floor ventilation as a priority - clear existing air bricks, add periscope vents where ground levels are high, and ensure cross-flow through the void. Correct external defects that are letting water into the substructure. Inspect all timbers for wet rot and replace anything compromised. Only then should thought turn to insulation upgrades or floor coverings, which if installed over a wet void will simply trap the problem.

Book a sub-floor inspection

If your property has any signs of low-level damp, cold floors, or musty smells at ground level, a borescope inspection of the sub-floor void is a fast, non-destructive way to understand what is happening beneath your home. Contact us to arrange a survey.