Building Pathology

Question 1

45 Cullen St. What are obligations under building regulations when replacing roofs?

Answer 1

1. Building control application required if more than 50% of the surface of the individual thermal element is renovated.
2. Ensure thermal insulation is sufficient by upgrading.

Question 2

45 Cullen St. Why did you advise replacing the cold roof with a warm roof?

Answer 2

Reduced risk of condensation and improved energy efficiency and energy bills.

Question 3

45 Cullen St. What additional benefits did you mention about implementing the warm roof system?

Answer 3

Reduced risk of condensation and improved energy efficiency and energy bills.

Question 4

45 Cullen St. How did you explain that the proposed warm roof system would satisfy Part L?

Answer 4

Insulation placed
between and over
joists as required to
achieve the target
U-value

Question 5

45 Cullen St. What U-Value did you need to achieve?

Answer 5

0.16 W/m2K as per Appendix C Table C1 AD L.

Question 6

What is a U-Value?

Answer 6

A measure of the ability of a building
element or component to conduct heat from a warmer environment to a cooler environment. It is expressed as the quantity of heat (in watts) that will
flow through 1m2 of area divided by the difference in temperature (in degrees K) between the internal and external environment. The unit is W/(m2K).

Question 7

45 Cullen St. Did you take a core sample of the roof?

Answer 7

I asked a roofing contractor to carry out this task and it was confirm there was no insulation and timber roof deck.

Question 8

45 Cullen St. Why was a liquid applied system not applicable?

Answer 8

The roof replacement was simple with no plant or penetrations. Felt was the favoured option and generally more cost effective, especially on a domestic property.

Question 9

18 Noel St. Explain the rationale behind advising the use of lime in the mortar mix.

Answer 9

Due to being Victorian soft bricks specified 1:3 / NHL 3.5.

Question 10

18 Noel St. What internal recommendations were made to address the dampness issue?

Answer 10

Ready mixed lime mortar at a ratio 1:3. Lime puty:Sharp Sand.

Question 11

18 Noel St. How did you Identify the DPC?

Answer 11

Wider mortar joint at the base of the wall.

Question 12

18 Noel St. What type of DPC was It?

Answer 12

Slate

Question 13

18 Noel St. If they continued to report damp issues despite implementing your advice, what additional steps would you recommend?

Answer 13

Advice that it can take many months for the wall to dry out. Heat the property.

Question 14

18 Noel St. Why did you recommend a French drain as well as guttering?

Answer 14

To allow rainwater to be directed away from the bay effectively and for water to evaporate from the ground.

Question 15

67 Holmes - How were moisture readings recorded and mapped?

Answer 15

Sketch of the wall including skirting, readings taking from moisture meter at different levels using a rule.

Question 16

67 Holmes - How was advice provided to address the condensation-related issues?

Answer 16

Improved ventilation and heating. External repairs. Replacement of plaster, wallpaper and skirtings.

Question 17

67 Holmes - How could the ventilation be Improved?

Answer 17

Mechanical and natural i.e. trickle vents to windows.

Question 18

67 Holmes - What could be causing the condensation?

Answer 18

Poor ventilation and heating in the property. Cold bridging and poor building performance.

Question 19

67 Holmes - What are long term effects, if the Issue Is not resolved?

Answer 19

Deterioration of the building and harmful to health for the tenant.

Question 20

St Hugh’s - What repair methods could be used?

Answer 20

Indent repairs to sandstone and re-pointing with lime mortar.

Question 21

St Hugh’s - Did you recommend any actions or solutions to address the issues identified with the mortar?

Answer 21

Yes, I recommended rake out and re-point.

Question 22

St Hugh’s - What mortar would you expect or use when repairing?

Answer 22

1:3 Lime (non-hydrated):Sand

Question 23

Four main stages of identifying and remedying building defects?

Answer 23

Inspection – A stringent
inspection process will identify clearly visible and less visible defects within a
building’s fabric.

Diagnosis – This is the second stage and it is essential for the Building
Surveyor to have knowledge and experience with regard to the wide range of various diagnoses for any given defect. This is effectively what is wrong with
the building and why. It is important to understand that there may be a
number of contributory factors to any one defect.

Prognosis – This stage involves predicting the consequences of not dealing
effectively with the defect and the likely short and long term implications to the
building in question.

Remedy / Remedial action – This is final step in rectifying the issue(s) in
hand and will form a key part of the recommendations of your findings to the
client. Building Surveyors may be required to recommend alternative
solutions, depending on cost and building longevity requirements.

Question 24

Limitations of a moisture meter?

Answer 24

Calibrated to timber, salts can trigger the meter and give false readings. Foil backed plasterboard can also provide false readings.

• Typically, readings of up to 18% moisture in timber are acceptable
  (dependent upon relative humidity of surroundings)
• Brickwork is considered wet at 5% and saturated at 10%
• Plaster is dry at 1% and saturated at 5%
  *
  Note: Readings above are based on the difference between wet and dry
  weight and not damp meter readings which can be misleading unless the
  readings are understood and interpreted correctly.

Question 25

Typical Building Pathology Defects

Answer 25

A material, component or finish which does not meet its expected
performance criteria’.
Some of the most common types of defects are listed below:-
* Penetrating damp
* Rising damp
* Condensation
* Carbonation
* Structural failure
* Corrosion

Question 26

Carbonation of Concrete

Answer 26

BRE DG 405
A concrete mix is naturally alkaline due to the presence of calcium hydroxide,
and this alkalinity (pH 12.5 to 13.5) confers a level of chemical protection to
embedded steel reinforcement. Where acidic atmosphere gases (such as
carbon dioxide, sulphur dioxide, and sulphur trioxide) are in contact with the
concrete and enter the matrix in solution through pores (permeability), cracks
and damaged areas, reactions between the alkaline material and acidic
solutions result in a reduction in alkalinity known as carbonation.
Carbonated concrete offers little protection to embedded metal, and corrosion
may occur. This, in turn, causes cracking and spalling of the concrete, which
allows further carbonation to take place.

Question 27

What are the two timber defects?

Answer 27

Wood rotting fungi are familiarly categorised as wet or dry rot. Whilst there
are numerous forms of wet rot, there is a single true dry rot, Latin name,
Serpula Lacrymans.

BRE digest 453

Wet Rot: * Essential requirement is a high source of moisture.
* Moisture content required is much higher than for dry rot.
* Wet rot can only survive in timber with an moisture content in excess of
40%.
* Wet rot can occur in well-ventilated spaces.

Dry Rot: * Spores present naturally in the air – potential to attack most buildings
* An essential requirement is a good source of moisture
* Opinion varies as to moisture content required but 20 – 22% generally
quoted
* Dry rot prefers still and damp air – and unventilated spaces
* Dry rot can spread and infest timber with a moisture content of 14 or
15% - This is why it is so destructive

Question 28

Explain the calcium carbide speedy test?

Answer 28

Rising damp in walls: diagnosis and treatment BRE DG 245

Works by testing a weighed sample of drilled masonry that has been taken from a sample area such as a mortar joint located above the damp proof course. This sample is then placed in a container. A measured amount of calcium carbide powder is placed in a separate portion of the container, and then the container is sealed. The container is shaken and the two substances mix together to trigger a reaction that produces acetylene gas if moisture is present.

The meter will indicate the results of the test. Readings will range from 0 to 5, with a higher number indicating a higher level of moisture.

Question 29

Name some invasive weeds?

Answer 29

Japanese Knotweed and Giant Hogweed.