Building Pathology - Damp and General Defects

Question 1

What is Damp?

Answer 1

A building is considered damp if the moisture becomes visible through discoloration and staining or finishes or causes mould growth, sulphate attack, frost damage or even drips and puddles

Question 2

How might you test for damp?

Answer 2

The use of a protimeter/ moisture meter or a speedy carbide meter can be used to establish the moisture content of walls, and level of damp occurring.

Question 3

What is a Speedy Carbide Meter?

Answer 3

It’s a devise to measure moister in masonry by slow drilling masonry, putting dust into a container with a know a measurement of calcium carbide. It releases a gas in proportion to the amount of moisture present.

Question 4

What is a moisture meter?

Answer 4

It is used to measure moisture content in wood. It measures the electrical resistance between two applied electrodes?

Question 5

How would you identify rising damp?

Answer 5

• High tide mark, peeling and
• blistering to finishes
• musty smell
• rotting of timber
• hydroscopic salts (attracts moisture)

Question 6

What are the common caused of rising damp?

Answer 6

• Absence of DPC

- Bridging of DPC b y pointing, render, soil, paving, mortar droppings.

Question 7

How would you remedy Rising Damp?

Answer 7

Remove DPC problems such as bridging. Consider injecting a chemical DPC where absent.

Question 8

How would you Identify penetrating damp?

Answer 8

It’s dependent of the levels of exposure of the building and only occurs in certain areas. the first sign is damp patches on walls ceilings or floors. tends to grow or darken after periods of heavy rainfall.

Question 9

What are the causes of Penetrating damp.

Answer 9

Driving rain through exposed masonry that have:

• Insufficient thickness
• Issue with cavity tray
• cracked or detached rendering
• defects to window cills
• blocked cavity ties.

Question 10

How would you remedy penetrating damp?

Answer 10

• Repointing of defective mortar joints
• Repair cracked/ damaged render
• application of masonry water repellent.
• inspect cavity trays and ties for blockages.

Question 11

What is a cold/ thermal bridge

Answer 11

A thermal bridge describes a situation in a building where there is a direct connection between the inside and outside through one or more elements that are more thermally conductive than the rest of the building envelope.

Question 12

How do you prevent cold bridging?

Answer 12

Cold bridging can be prevented by using materials with better insulating properties, or with an additional insulating component, called a thermal break.

Question 13

What is condensation?

Answer 13

Condensation occurs when warm air collides with cold surfaces and condenses depositing water droplets.

Question 14

How would you identify condensation in a property?

Answer 14

The presence of water of the inside of windows or other cold surfaces. Black mould can be a common indicator in areas where moisture is present and cannot dry out.

Question 15

What interstitial condensation? Where else might it occur

Answer 15

Interstitial condensation occurs when moist air penetrated inside a cavity of a structure such as the roof, walls or floors elements

Question 16

You noted that the glazing at Aldershot Road had interstitial condensation. Why would this occur and what did you advise?

Answer 16

It is condensation that occurs on the inside insulated glass unit (IGU). Only occurs where the hermetic seal has failed.

It is possible to repair the seal, however, I recommended replacement.

Question 17

What are the common caused of condensation?

Answer 17

Often in rooms where air can become humid such as kitchens and bathrooms. Condensation will be present where there is a lack of insulation and ventilation.

Question 18

How might you you remedy condensation?

Answer 18

• Natural/ Mechanical ventilation
• reduce moisture generation
• provide adequate heating,
• insulate or remove cold bridges if present.

Question 19

What type of defects might be common to commercial Georgian properties with stone facades?

Answer 19

Regent Street Disease

Question 20

What is Regent Street Disease and how might you remedy it?

Answer 20

WHAT IT IS!

• It occurs in buildings constructed using a steel frame covered in facing masonry or stone.
• often found in early twentieth century buildings where stone units are tightly built around the steel frame.
• The porous stone allows moisture to get into the steel structure, which corrodes, increases in size, putting pressure on the masonry causing cracking.

REMEDIES!

• Removal of masonry, sand blast steel, apply protective coating.
• Cathodic protection (reverses direction of electric current associated with corrosion. However doesn’t make good to existing.

Question 21

How long would leave Damp bricks/ plaster to dry out before commencing works?

Answer 21

3-4 months is recommended. However a dehumidifier can speed up the process.

Question 22

How would you tell the difference between RISING DAMP and CONDENSATION with a moisture meter?

Answer 22

• Rising damp comes from the ground. By taking reading at 300mm centres going up the wall the damp will decrease form bottom to top, an there will be no damp above tide mark.
• Condensation will cause uniform dampness. Mostly in cold spots such as corners and windows.

Question 23

What are the common defects found in a Victorian property (1837-1901)

Answer 23

ROOF
- Overloading of structure (concrete tiles)
- Roof spread (failing collar tie)
- Failing rainwater goods.
- Chimney lean.
WALLS
- No DPC (rising damp)
- Bulging walls caused by snapped headers/ poor restraints. 
- Timber decay
FLOORS
-Blocked air bricks
- Timber decay
FOUDATIONS
- Inadequate foundations susceptible to subsidence and cracking 
DELETERIOUS MATERIALS 
- Lead paint

Question 24

What remedial works did you specify for the cut edge corrosion found at Camfield Road?

Answer 24

I specified a proprietary cut edge corrosion treatment applied to effected lap ends and fixings.

Question 25

What coatings are usually found on sheet metal?

Answer 25

Plastisol Coating or PVF2 (Poly vinyl Floride)

Plastisol is often identified by a leather effect. PVF2 Is a thinner material with a smooth finish.

Question 26

What are the main type of masonry defects?

Answer 26

• Frost damage
• Efflorescence
• Sulfate attack
• Wall tie failure
• Weathering

Question 27

What is sulfate attack? and how would you remedy it?

Answer 27

CAUSE - Reaction between sulphates within the brickwork. When wet soluble sulphates react with portalnd cement, causing mortar to expand/ crack.

Chimneys are susceptible due to sulfate containing gas produced by fuel appliances.

REMEDY - Replace defective masonry/ mortar, install additional protection such as DPM, line chimneys if applicable.