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Failed chemical damp proofing treatment

The main reasons for avoiding chemical damp proofing treatment are:

  1. Damage – Drilling into a wall to install chemical damp proofing, damages walls.
  2. Misdiagnosis – Chemical are used against rising damp, but rising damp is exceptionally rare. It is far more common that the problem is penetrating damp. If penetrating damp goes untreated it is likely to lead to greater problems, such as Dry rot.
  3. Damage to neighbours – The silicone thixotropic cream, such as DryZone by Safeguard causes a change in the absorption of moisture. This can be beneficial, but can lead to neighbours properties suffering from dampness, which can lead to a case, which would almost certainly lead to damages if no Party Wall etc Act 1996 agreement is entered.
  4. Disruption and cost – Chemical damp proofing is the most disruptive and costly form of damp control. As a minimum double check your sub-floor and internal relative humidity (see Dataloggers) before considering disruption and expense.
  5. Ongoing cost – It is common to have to retreat a damp proofed wall every few years, especially if the root cause was not rising damp.
  6. Diminution of value – Damp proofing a property is liable to reduce its value given the need for ongoing treatment, especially if the root cause was not rising damp.

Problem caused by chemical damp proofing

When the root cause was condensation

Chemical damp proofing often causes costly remediation especially if rising damp is misdiagnosed. This is because absorbent plaster is typically replaced with impermeable (non-absorbent) damp proofer’s slurry, which hides but does not stop the source of water.

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Here is a flat with excess humidity causing dampness along the interface between the original and new plaster.

If as is commonly the case, condensation was the root cause. Excess humidity can become trapped at the interface between the original permeable plaster and impermeable slurry. This damage results from two damp proofing treatments from London’s leading contractor.

When root cause was hygroscopic salts


Above is a house with hygroscopic salts which migrated to the neighbours after damp roofing treatment

In this case chemicals were injected following misdiagnosed rising damp. The damp proofing treatment resulted in hygroscopic salts migrating through to this, the neighbour’s wall. The neighbour is set to win compensation, in part because there was no party wall agreement.

When misdiagnosed rising damp resulted in Dry rot

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In this case the property had chemical damp proofing treatment against rising damp. There was no rising damp, but a source of water, likely to be condensation on a cold water pipe, which resulted in Dry rot to the sub-floor void.

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