Building Elements

Question 1

What issues are associated with timber sash windows and what are the potential repair options?

Answer 1

wet rot - beadings etc designed to be sacrificial

splicing - hard to achieve accurately and can result in differential movement.

resin repair - can be sanded and painted in a day and undertaken in situ

Consider provisional sums

Question 2

What issues are associated with steel windows and what are the potential repair options?

Answer 2

up to 1950s steel windows were coated in a cold-dip methods in which a lead paint was applied. Remove of lead paint is hazardous. The bottom rail or cill is liable to rust first.

Question 3

When was cavity wall construction introduced?

Answer 3

Prevalent from Mid-20th century, post war.

Question 4

What are typical defects associated with cavity walls?

Answer 4

Mortar snots and debris within the cavity causing cold bridging

Gaps between insulation

inadequate wall tie provision

missing cavity trays or inadequate detailing of cavity trays with insufficient laps.

Question 5

What are different causes of cracking in walls?

Answer 5

Wall tie failure

Thermal movement

calcium silicate brickwork

ground movement - heavy and subsidence

Inadequate provision of movement joints

Question 6

How do you identify wall tie failure, what is it caused by and what remedial measures are there?

Answer 6

Caused by the corrosion of galvanised steel wall ties

Indicators of wall tie failure include horizontal cracking along bed joints at 450mm centres or random bulges.

Borescope used to confirm presence of corroded ties.

Wall tie (metal) detectors can be used to locate the position of ties.

The wall ties can then be cut out and replaced with stainless steel ties mechanically fixed using an epoxy resin.

Question 7

How do you identify thermal movement in masonry walls, what is it caused by and what remedial measures are there?

Answer 7

Typically displayed as brickwork sliding off a damp proof course or cracking at corners caused by the expansion of the masonry

Movement joints should be provided to allow for adequate movement.

Question 8

What are aluminium composite material cladding panels?

Answer 8

External wall cladding systems comprises of two aluminium sheets encasing an insulation or filler core material.

Question 9

Why are aluminium composite materials considered dangerous?

Answer 9

Void - the fixing system typically allows a cavity between the insulation and the aluminium panel which if installed without cavity closers can cause a chimney effect providing a route for the external spread of fire.

combustibility of filler - A number of the insulative materials used are combustible.

performance of aluminium skin during a fire is critical as can delaminate exposing the inner core.

Question 10

What are typical defects with timber frame buildings?

Answer 10

Cill beam most vulnerable to rot.

inappropriate alteration removing supporting structural members

In historic buildings the wall may not be sufficiently ties and gable ends may be leaning.

wood boring insects

fungal attack

Question 11

What are typical defects associated with raised access floors?

Answer 11

Rocking caused by loose tiles

Needs to earthed

Question 12

What are typical defects associated with composite floors and what are the remedial options?

Answer 12

Diagnosis

• Vibration due to lightweight construction used to provide structural economy.

Repair

• Stiffening with support beam would help but difficult to practically achieve in an occupied building
• change fitting that rattle
• Best considered during fitting out - a detailed analysis can identify areas most prone to vibration and situate walkways to avoid these areas.

Question 13

What are typical defects associated with filler joist floors and what are the remedial options?

Answer 13

Diagnosis

• Found in buildings construct during the second half of the 19th century up to 1925.
• Steel joists at 0.6 to 1m centres and space between filled with concrete often formed using coke breeze or other lightweight material.
• Usually identified by parallel cracks in line with joists where they have corroded.
• May need to open up to determine extent of section loss to web of the steel.

Prognosis

• Coke has a high sulphur content making the concrete an acidic rather than alkeline environment, with the presence of moisture and oxygen can turn to sulphuric acid which is highly corrosive and can attack the steel resulting in section loss.

Repair

• Address cause of moisture ingress
• Resin injection treatments are available which can be drawn under vacuum
• If serious section loss than may need to replace steel.

Question 14

What are typical defects associated with woodwool permanent formwork and what are the remedial options?

Answer 14

Used between 1950-1970’s as a formwork and means of providing permanent insulation

Difficult in knowing whether reinforcement has been placed properly with appropriate cover as often spacer blocks are missing or concrete that has not been properly compacted, causing honeycombing around the rebars. This could compromise strength and fire resistance.

Intrusive investigations are often required.

A remedial solution would be to use sprayed concrete to the underside of the soffit following intrusive investigation to confirm its condition.

Question 15

What are typical defects associated with reinforced aerates concrete planks and what are the remedial options?

Answer 15

Planks produced prior to 1980. Prone to deflection and cracking. Need to check for evidence of cracking to soffit, and condition of roof covering.

Question 16

What are typical defects associated with strammit roof decking and what are the remedial options?

Answer 16

An insulation board often used as roof decking, straw sandwiched between building paper

Material had a very low resistance to moisture and would decay and become fragile

May need to be replaced if in poor condition.

Question 17

What are typical defects associated with a ground bearing slab and what are the remedial options?

Answer 17

Issue with cracking due to early drying shinkage, as result needs either formed or induced movement joints at 6m intervals.

Induced joints can be cut to 25% of slabs depth filled with a soft flexible sealant.

crazing can occur to the power floated surface, characterized my map pattern of hairline cracks around 0.1mm in depth.

Historically not laid onto DMP or DMP not lapped with DPC to provide continuous barrier to moisture, causing rising damp.

Question 18

What are typical defects associated with a damp proof course and what are the remedial options?

Answer 18

Historically, made of slate, asphalt and lead.

Often not that they fail but that they are compromised such as by high external ground levels.

Inadequate laps on polyetheylne DPC

injected DPC may not be necessary. Important to address the source of moisture and then consider how the building may have been altered in a way that impacts the effectiveness of the DPC.

Question 19

How might moisture ingress issues in basements be addressed?

Answer 19

Tanking

retrofitting drainage cavity membrane - uses a profile polythene membranes applied to the wall and floors to form a drained cavity which drainage to a sump pump.

Question 20

What is radon and how can it be managed?

Answer 20

Radon is a radioactive colourless gas that is naturally present throughout most of the UK emitted from radioactive elements such as uranium that are naturally present in rocks and soils.

Radon typically dissipates into the atmosphere but in confined unventilated spaces such as basements the concentration levels can become dangerously high, causing cancer.

Concentrations can be measured in Bacquereles per cubic meter and remedial measures include inserting protective barriers within floors and wall or mechanical ventilation systems.

Question 21

What are typically defects affecting foundations?

Answer 21

Subsidence
Heave
Settlement
Sulphate attack

Question 22

What is subsidence and what causes it?

Answer 22

Subsidence is the downward movement of the ground caused by activity in the ground, including removal of water from the ground in clay soils, soil erosion due to ground water or leaking drains.

Question 23

What is heave and what causes it?

Answer 23

The upward movement of the ground. It is typically caused by increased water content in the ground expanding the earth and forcing the structure upward. This can be caused by the removal of trees of in extremely cold weather where freezing of the ground occurs.

Question 24

What is settlement and what causes it?

Answer 24

Downward movement of a building brought about by the pressure from the foundation causing compression of the ground. If settlement it differential it can result in cracking. Usually occurs in relatively new buildings.

Question 25

What is the difference between subsidence and settlement?

Answer 25

Settlement typically occurs in recently constructed buildings and it caused by the compaction of the earth underneath the foundation. Subsidence can happen at any stage in a buildings life and is typically caused by the downward movement of the ground brought about by changes in the conditions in the ground such as adjacent excavations or soil erosion removing support to foundations.

Question 26

What is underpinning and when might it be necessary?

Answer 26

Underpinning is the extension of the foundations downwards to reach more stable ground.

It may become necessary due to subsidence, adjacent building excavation or when additional storeys are to be added either above or below ground level.

Question 27

Briefly outline what types of underpinning you are aware of?

Answer 27

Mass concrete - involved excavating systematically in adjoining bays beneath the foundation, filling it with concrete and then punning up the gap between the old and new foundations.

Pier and beam - a reinforced concrete beam is installed in the wall just above the existing footing, prior to discrete pits at intervals beneath the modified wall. The pits are filled with concrete and pining carried out.

Pile and beam - Piles are installed either side of the wall and beam are inserted through the wall to join the tops of the pile.

Minipiles

Question 28

What are common causes of defects?

Answer 28

Inappropriate specification

Poor quality of manufacturing or construction

Poor workmanship

Failure of routine maintenance

Question 29

What typical defects are associated with mastic asphalt roofing?

Answer 29

Blistering: Blistering of asphalt is a common problem, often due to:

• poorly detailed upstands;
• a failure to provide effective vapour control; or
• water ingress into a roof deck.

Cracking: Cracking is often found around junctions with alternative construction, perimeter details and projections as a result of differential movements in the background materials

Slumped upstands

Crazing caused by UV degradation

Question 30

What are typical defects associated with flat roof?

Answer 30

Leaks

lack of insulation

penetration caused by plant equipment

inadequate falls

Question 31

What are typical defects associated with pitched roofs?

Answer 31

roof spread due to increased loading caused by replacing original roof covering with concrete tiles

corroded tile nails

delaminated slates

inadequate ventilation

inadequate insulation

poor quality temporary repairs

cutting through structural roof member to create additional loft space

Question 32

What are typical defects associated with parapet details?

Answer 32

Leaks caused by lead poorly formed into outlet, or insufficiently large laps on lead.

Copings not sealed, or cracked.

The main body of the parapet is not separated by a damp-proof course, allowing water to track down into internal walls.

Blocked outlet or hopper

Question 33

What are the main repair options for roten timber sash windows?

Answer 33

Splicing: expensive and difficult to practically achieve without removing window. New wood will typically expand differently to existing.

Resin Repair: This is not approved by all conservation officers, who may regard it as a dishonest repair. However, if approved, a window can be preserved very effectively with minimal interference using site-based work. The work can be sanded and painted in a day. This work can be undertaken by a carpenter on site without the need to remove the glass.

Question 34

What are the main issued with steel windows?

Answer 34

Lead paint: Up to the 1950s, metal windows were coated using a cold-dip method in which red lead paint was applied.

Corrosion: The bottom rail or ‘cill’ is liable to rust first as it is more vulnerable than the jamb and head.