Building Pathology

Question 1

Name some of the common Concrete Defects found in Concrete Framed Structures ?

Answer 1

1. Concrete Carbonation
2. Chloride Attack (Salts added to the concrete - sea water in unwashed sand)
3. Concrete Cancer (Chemical in cement reacts with Silica (in aggregates) to form a gel substance which absorbs water and cases cracking

Question 2

What is Concrete Carbonation ?

Answer 2

It is where steel reinforcement within the concrete corrodes causing it to expand and cause cracking and spalling to the concrete.

The corrosion is caused by carbon dioxide in the air that reduces the natural alkalinity of the concrete and forms calcium carbonate that allow the steel to oxidise and corrode.

It is exacerbated by the presence of water and happens quicker in low quality concrete.

Question 3

How do you test and repair for Concrete Carbonatation ?

Answer 3

TEST

• Drill x2 core holes to break out concrete in-between
• add chemical indicator (pink colour= No carbonation is present)

REPAIR

• Anti Carbonation coating (10 year life expectancy)
• Re- Alkalisation using low voltage current (wet and messy job)
• Small Repairs - Clean with high alkaline passivating system (zink solution) , wire brush and faceup with epoxy mortar and bonding argent.

Question 4

How is a Cold Deck Roof formed ?

hint- Insulation below deck to temperature is colder/warmer depending on weather

Answer 4

• Waterproofing (roof finish)
• Deck
• Void of Ventilation/ Joist
• Vapour Barrier
• Ceiling

Disadvantage - Loss of head height , difficult to get to to joists . Issues with Thermal Bridging. Requires lost of ventilation (at verge and mushrooms)

Question 5

How is a Warm Deck Roof formed ?

hint- insulation above deck so deck temp is close to temp of building

Answer 5

• waterproofing (roof finish)
• insulation
• Vapour Barrier
• Deck

Disadvantage - need more height which could effect doors and parapets etc)

Question 6

What are the typical defects of a 1930’s building ?

Answer 6

• Cavity Wall Tie Failure ( use metal detector, snapped headers, horizontal cracking. Add new ties- drill through both bricks and epoxy resin and insert tie)
• Cast iron gutters faulty and cracked
• No/ spent sarking felt
• Small windows, need to updated for means of escape
• Dry Rot / Wet Rot
• Damps
• Shallow Foundations - Subsidence / heave
• Poor subfloor ventilation

Question 7

What is a Deleterious Materials means

Answer 7

The term ‘deleterious materials’ is a broad one, encompassing not only the materials that are dangerous to health or which are the causes of failures in buildings, but increasingly, materials which are environmentally damaging.

Question 8

What Deleterious (Hazardous) Materials are there ?

Answer 8

• Asbestos and Asbestos Containing Materials (ACM) (found in paint, floor, insulation, pipework)
• Lead piping and paints
• Woodwool slabs (used in decking for roof slabs- becomes week and has poor performance)
• MOST RECENT - Magnesium Oxide boards (external wall insulation) . Chloride salts (hydroscopic) and absorbing air moisture thus corroding metal components (cladding could fall off)

Question 9

You mentioned that you attended a property with damp?

Answer 9

1. Leak to bathroom tap
2. Timber decay
3. Soil stack saturating wall
4. Rising damp (1m from ground)