Module 1 Assessment — Moisture, Air and Materials — Damp, Moisture and Building Pathology — Level 2

Question 1 of 14A room is at 20°C and 60% RH. Outside is 5°C and 80% RH. In which direction is vapour being driven through the external wall?
Inward, because the outside air has the higher relative humidityOutward, because the inside air has roughly twice the vapour pressureNeither — the two are in balance because the difference in RH offsets the difference in temperatureInward in the day and outward at night
Question 2 of 14Air at 10°C and 90% RH is heated to 20°C with no moisture added or removed. What happens?
The relative humidity stays at 90% because the water content is unchangedThe relative humidity falls to roughly 47% and the mixing ratio is unchangedThe mixing ratio falls because warm air holds less waterThe dew point rises because the air is warmer
Question 3 of 14 · select twoYou want to know whether one room is genuinely holding more moisture than another. The two rooms are at different temperatures. Which TWO measures let you answer that?
Relative humidity in each roomMixing ratio in g/kgAbsolute humidity in g/m³Surface temperature of the coldest wall in each
Question 4 of 14A coarse, open material such as clean gravel carries capillary water further upward than a fine-pored material.
TrueFalse
Question 5 of 14You are investigating a solid brick wall with staining to 800mm. You take drilled samples at 25%, 50% and 75% of the wall thickness. The result is dry at the internal face and progressively wetter towards the external face.What does the shape of this profile most strongly indicate?
Condensation on the internal surfaceWater arriving from the external side or from below, not from the roomHygroscopic salts in the internal plasterNothing — a profile cannot indicate direction
Question 6 of 14Nitrate salts are found in high concentration in plaster at the base of a wall. What does this most reliably indicate?
A recent plumbing leakCondensation over several wintersLong-term contact with ground water carrying products of organic decompositionSulphate attack on the cement in the render
Question 7 of 14A wall's plaster shows a total moisture content of 4.2% and a hygroscopic moisture content of 3.9%. What does this tell you?
There is substantial active water ingress to findAlmost all the moisture is held by salts absorbing from room air; there is little active ingress to explainThe sample was contaminated and must be retakenThe wall is below its equilibrium moisture content
Question 8 of 14 · select twoWhich TWO of the following will invalidate a gravimetric moisture content result?
Leaving drilled samples open to room air before sealing themDrilling quickly with a blunt bitTaking samples at three different depthsRecording the material and the depth of each sample
Question 9 of 14Why is a room relative humidity of 55% not sufficient evidence that mould risk is controlled?
Because 55% is above the 50% threshold for mould germinationBecause mould responds to the relative humidity at the surface, which is governed by surface temperature and may be far higher at a cold spotBecause relative humidity meters are not accurate below 60%Because room RH must be measured at floor level to be valid
Question 10 of 14A resistance moisture meter reads at the top of its scale on salt-contaminated plaster holding modest hygroscopic moisture. Why?
The meter is faulty and needs recalibratingConductance is dominated by dissolved ionic salts, which the instrument cannot distinguish from waterPlaster always reads high because of its densityThe pins were not inserted deeply enough
Question 11 of 14Which of these statements about a meter reading would survive a competent challenge in a report?
"Moisture readings of 25% were recorded to the base of the wall.""The wall was found to be suffering from rising damp with readings of 25%.""Elevated wood moisture equivalent readings were recorded across the lower 900mm, falling to background above that line; gravimetric samples were taken to establish actual moisture content.""The meter confirmed the presence of damp."
Question 12 of 14Softwood at 20°C is at 19% moisture content. What is the most useful thing this tells you?
Nothing — 19% is unremarkable in any materialThat it is in equilibrium with roughly 85% RH, and is at or near the threshold where wood-decay fungi become viableThat it has been in direct contact with liquid waterThat the surrounding air is at 19% relative humidity
Question 13 of 14A ground-floor room in a solid-walled Victorian terrace has staining and perished plaster to approximately 900mm above floor level. A resistance meter reads at the top of its scale across the affected band and drops to background above it. The owner has been quoted for a chemical damp-proof course on the strength of those readings.Set out what you would do to establish the mechanism before accepting or rejecting that diagnosis, and explain what each step would tell you.
0 words · at least 60 needed.
Question 14 of 14A landlord has installed a new extractor fan and turned the heating up in a flat where a tenant reported mould in a bedroom corner. A month of logged data shows the room's average relative humidity has fallen from 68% to 54%. The mould has returned in the same corner.Explain, in terms of the physics, why the fall in relative humidity does not by itself show the problem is solved, and what you would measure next.
0 words · at least 50 needed.