Dampness

Question 1

What different types of dampness are there?

Answer 1

• Penetrating damp
• Rising damp
• Condensation

Question 2

What is the definition of rising damp?

Answer 2

Upward movement of water through a porous material due to capillary action

Question 3

How do you identify rising damp?

Answer 3

BRE Digest 245 set out diagnosis method:

• Water approx. 1m high
• Salt deposits will be visible where water have evaporated and leave a tide mark
• Peeling of wall finishes
• Musty smell, rotting timbers (skirting)
• Usually where there is no DPC or where the DPC has been bridged

Question 4

What causes rising damp?

Answer 4

• Lack of a DPC - only a requirement after 1875
• Damaged DPC - brittle slate, or penetration through a membrane
• Bridged DPC - external landscaping/ground level raising

Question 5

Where should a DPC be located?

Answer 5

Should be 150mm above ground level

Question 6

What materials would you expect a DPC to be constructed from?

Answer 6

• Pre 1900 - slate
• 1900s onwards - bitumen
• Modern - polymer materials

Question 7

What are the treatment options for rising damp?

Answer 7

• Insert a DPC - either physically or chemically injected

- Hack off all blown plaster and replace with breathable/waterproof plaster or render

Question 8

What is the process with physically retro-fitting a DPC?

Answer 8

• Cut out the brickwork and insert (access required from both sides)
• Can cause issues with services within wall
• Very costly and very disruptive

Question 9

What is the process with chemically injecting a DPC?

Answer 9

• Holes are drilled in brickwork at 120mm centre
• Chemical cream is injected at low pressure
• External holes should then be plugged
• Must be allow to dry before plastering
• Can be difficult to ascertain the quality, best to ensure a guarantee for the work is provided

Question 10

What is the definition of penetrating damp?

Answer 10

Penetrating damp is caused by moisture passing through a building fabric

Question 11

What is the cause of penetrating damp?

Answer 11

There are a number of possible causes, often due to construction, design or material failure:

• failed rain water goods
• failed roof coverings
• fixing penetrations in building fabric
• installation of services
• defective cavity tray
• burst water pipe

Question 12

How would you identify penetrating damp?

Answer 12

If the profile of the dampness is consistent with whatever the suspected cause is. Thorough inspection required, and should be aware that moisture can track within buildings

Question 13

What tests are available for penetrating damp?

Answer 13

A die test, when water with a die in it is applied to a suspected ingress point, and if the die comes through to where the damp is manifesting you can link the two

Question 14

What is condensation?

Answer 14

Condensation is when moist air comes into contact with a surface with a lower temperature than the due point

Question 15

What is the cause of condensation?

Answer 15

Condensation is caused by moisture in the air, from normal activities and cold surfaces

Question 16

How would you identify condensation?

Answer 16

Condensation forms on cold surfaces, like windows and insulated areas - it will be visible on the surface

Question 17

What are the consequences of condensation in a building?

Answer 17

Condensation can increase the moisture content of timber, which can in turn lead to rot/infestation
Condensation occurring on plaster walls can allow mould growth, with can be detrimental to health

Question 18

What treatment is available for condensation?

Answer 18

• Increase natural ventilation (trickle vents, open windows)
• Install mechanical ventilation (extract in toilets and kitchens)
• Avoid drying clothes indoors
• Improve insulation and double glazing
• Ensure adequate heating
  (Essentially, warm the surfaces to stop them achieving the dew point, and reduce the moisture content in the air)

Question 19

What is interstitial condensation?

Answer 19

Interstitial condensation is condensation that occurs within a void or cavity where there is insufficient ventilation, insulation or absence of a vapour control layer

Question 20

What is thermal bridging?

Answer 20

Thermal bridging, often known as cold bridging, is caused where there is direct contact between internal and external faces of a building due to thermal properties of the fabric being poorer than that around the area. Will often cause localised condensation and therefore mould growth

Question 21

What tools would you sure to detect moisture?

Answer 21

• Speedy carbide meter
• Thermographic imaging
• Electrical resistance meter
• Capacitance meter

Question 22

What is a Speedy Carbide Meter?

Answer 22

It’s used to test samples of material extracted, to establish the moisture content. It provides an accurate reading of the moisture content, but can require destructive testing and will most likely need to be sent away or brought back to the office etc. for definitive results

Question 23

How is thermographic imaging used to detect moisture?

Answer 23

Moist areas will generally be a lower temperature. Can be used to detect cold bridging as well

Question 24

What is an electrical resistance meter?

Answer 24

It measures moisture with a current that passes between two prongs. It is only calibrated for timber, though can be used as a comparison in other materials. Easy to use and causes minimal damage, can also react to salts so should be used with caution

Question 25

What is a capacitance meter?

Answer 25

It uses sensors to measure fringe capacitance, which varies with moisture content. Can be used on a number of different surfaces and materials