30 year chimney damp issue resolved!

Chimney Damp in Oxfordshire

Diagnosing Chimney Damp in a 18th century Oxfordshire home

Earlier this month, we travelled to Oxfordshire whereby our instruction was to diagnose the controlling factor of dampness on a chimney breast. The dampness has been a long standing issue for our client, whereby many attempts to resolve the damp have been undertaken. The solid wall had been sealed with a modern brick sealant and internally the breast re-skimmed in a gypsum plaster finish. The external walls were also peppered with chemical DPC holes!

Although many repair attempts to resolve the dampness had been carried out, not once had a diagnosis of the damp been achieved. The aim of my inspection was to diagnose the source of the dampness and provide repair guidance. Upon inspection, the appearance of the chimney breast  looked to be characteristic of salt related damp. Unknown by many, the long term burning of fossil fuels can induce the contamination of salt in chimney masonry and wall surfaces.

Often, and rightly so the immediate action to take when a building suffers from chimney dampness is to inspect the chimney itself. Repairs had been made to the chimney such as re-pointing and flaunching. The chimney had been repaired and stood in good condition but the dampness still persisted! The adjacent wall surface also appeared to be in good condition, with mortar and brickwork being in a perfect state. Salt dampness was the probable cause however how could this be confirmed? Again, we used Gravimetrics to provide a conclusive evidence of a diagnosis.

In the areas of prominent dampness, from approximately 500-1000mm, a free moisture content of less than 0.5% was evident. The controlling source of moisture in this area of the chimney breast was infact salt, with a hygroscopic content dwarfing the free moisture content. We also carried out salt analysis which revealed high levels of Chloride and Nitrates. Gravimetrics also revealed a large free moisture content at the base of the chimney breast which would correlate with high external ground levels. A combination of rising ground moisture as a result of high external ground levels in addition to the salt contamination of the breast could be confirmed as the controlling factors of dampness.

Finally, the client had an answer as to what the controlling source of moisture was on the chimney breast. Repair guidance in the form of both modern and traditional solutions was provided for the client to consider.

A thirty year damp issue, diagnosed in one inspection!

Oscar