Lower ground floor flat in Victorian converted building. Solid floor, radiator was found to be leaking.
- Leaks on solid floors can spread-out some distance.
Leak from heating system made worse by condensation, with a risk of penetrating damp.
Chemicals have been injected, as treatment for rising damp. This is involves replacing plaster with slurry.
The main concern is a damp stain to the front bedroom under the bay window accompanied by mould and salts.
Mould grows where relative humidity exceeds 85%RH for 6+ hours. Excessive humidity results from insufficient ventilation, poor air circulation and a cold surface.
The skirting board is made of MDF it is damp in a number of places including by both radiator pipes.
The brown teabag like discolouration comes from water moving through building material bringing colour with it. By contrast condensation is generally colourless.
There are calcium sulphate salts on the surface. Calcium sulphate is a key ingredient in cement and other building materials. If diluted in water salts tend to move to the surface. These can be removed with sandpaper and decorated.
Using a damp meter in radio frequency mode I have identified high levels of damp in the corner.
Water reflects radio waves at a set frequency similar to mobile phone shields. Meters can’t differentiate moisture from other dense matter such as metal and concrete. They help trace damp in a normal, homogeneous wall. Readings below 300 REL indicate that a wall is dry below the surface, 999 REL is the limit. Meters are for scanning, see surveyor.tips/profile.
Mould is inhibited by nitrates found in groundwater. The presence of mould at the bottom of a wall eliminates rising damp, or rainwater that has percolated through soil.
We found the leak in the left-hand radiator pipe. This is probably the root cause of damp to the front wall.
The only way to determine if the radiator is the sole cause of damp is to repair the leak, check the pressure and monitor the wall for dampness over an extended period of many months.
The thermal image where blue is ~ 5° colder than yellow shows the wall is not being warmed by the radiator.
Consider speeding up the drying process with a fan and dehumidifier set to a low level of relative humidity, with heat from the raditor.
A dehumidifier has been running for the last few weeks.
The mould and damp pre-dates the use of a dehumidifier.
There is what looks like mould across the flank wall above the radiator.
In this image there is a line about 1.3 m off the ground. This looks like the line of damp proofer’s slurry. Typically the lower section of a wall is replaced with impermeable slurry. This reduces the room is ability to absorb moisture and buffer humidity changes.
There is a high damp meter reading at the top of the front bedroom flank wall.
There is a damp spot in the front room which appears to come from past condensation.
Immediately outside there is hole in the wall and large Metal gates that is acting as a thermal fin.
Metal will draw heat out of a room. The secondary cause of high relative humidity is low temperature relative to the source of humidity, see surveyor.tips/humidity. Relative humidity is a measure of how much vapour is in the air compared to air’s capacity to hold vapour. It is a function of vapour pressure (quality of vapour) and temperature. As temperature rises, air can hold more vapour. Conversely as temperature drops, air holds less vapour until it meets the dew point at 100%RH, when dew or condensation forms.
External holes should be filled, ideally lime, which doesn’t trap moisture and allows some movement. However, most builders use cement. The repointing uses a cement-based mortar. So unless you plan to repoint, pragmatism should outweigh purism.
There is a retaining wall setback from the front window with a drain in the centre.
There are many cracks on the retaining wall that should be filled as a matter of good property management.
I highlight some cracks. All cracks should be filled and checked regularly.
The crack to the front right-hand corner should be raked out and filled.
The rainwater from the main roof runs under the concrete area to the front, near the internal damp patch.
We tested the flow through the drain using a hose. The pipework is hidden. There could be a leak from rainwater goods.
There are many defects around the front that could cause penetrating damp.
I doubt the crack in the windowsill would result in damp in the corner of the property, but it could and should be filled as a matter of good property management.
There are also cracks around the concrete in front of the property that should be filled. The above lists this is not exhaustive.
The soil to the front could cause water to percolate down. However, rainwater is bound to pick up nitrates.
The mould by the damp at the base of the front bay, suggests that the open areas of soil to the front is not the root cause of damp, but it cannot be fully eliminated.
There is what appears to be a damp stain on the wall by the rear door.
At the time of the survey the stain was dry, this suggests that condensation was a factor.
There are two areas of flaking paint by the kitchen. Above the radiator was dry at the time of the survey.
On the other side of the wall, the plaster is damp.
Again I would suggest that this is probably a form of condensation, possibly resulting from drying clothes on the radiator. It looks like the fresh plaster was not prepared with a drizzle coat, that is a deleted coat of paint, 2 or 3 to 1, pate to water.
Slurry results in internal walls becoming vulnerable to damp. Electrical wires run from under the cold sub-floor and therefore can cause heat loss increasing the risk of condensation.
The above is from a datalogger left in the property.
Relative humidity is a measure of how much vapour is in the air compared to air’s capacity to hold vapour. It is a function of vapour pressure (quality of vapour) and temperature. As temperature rises, air can hold more vapour. Conversely as temperature drops, air holds less vapour until it meets the dew point at 100%RH, when dew or condensation forms.
Dew point is also a proxy the vapour pressure. The higher the temperature the more evaporation will take place.
Surface relative humidity
The surface relative humidity is calculation based on temperature difference between the cold-water pipe and the temperature of the datalogger.
In conclusion from the datalogger
We can say with reasonable certainly that;
- The relative humidity is never too high and heat never too low.
- You have consistent relative humidity and heat.