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Buildsure Associates Newsletter - May 2016

External Wall Cladding.

A. Maintenance.

The most common consequence associated with faulty wall cladding is the “leaky” building. The reason, in most cases, is due to a lack of maintenance. There is a popular, although unfortunate misconception that all exterior cladding does not require any maintenance. Dangerous and costly consequences are inevitable with this mind set. “This lack of house owner and occupant knowledge suggests there would be benefits from requiring that they be provided with a maintenance schedule for their house, similar to a car handbook!” (See Note 1)

Firstly, we have to state emphatically that every built property requires maintenance and on a regular planned basis. The word “MAINTENANCE” derived from “MAINTAIN” is to allow all elements to function as originally designed.

The biggest investment made is usually YOUR house. It is therefore logical that you would want to protect that investment and by doing so enhance the value via your home’s capital gain: This is achieved by properly maintaining your property.

The Building Act states :(ii) “the need to ensure that maintenance requirements of household units are reasonable: (iii) the desirability of ensuring that owners of household units are aware of the maintenance requirements of their household units:” (See Note 2)

Buildsure Associates Ltd as part of their house assessments requires that the owner or their agents to have a competently prepared maintenance schedule for that building. This would detail a scheduled maintenance regime of what needs to be looked at, when it should be looked at, how to undertake the inspection, what to look for and what action to take if there is a possible failure.

B. Monolithic Cladding.

Background Information.

  1. A major problem for the home owner is the subsequent escalation in the response to water ingress. Between the period of around 1998 and 2004 timber framing did not have to be treated providing it was kept dry. This cost saving to developers/builders using untreated timber amounted in the region to a cup of coffee a day for six months. The costs of this minimal saving for the house owners who suffered moisture ingress (The Leaky Building Syndrome) in terms of dollars is many, many millions. This does not include the resultant stress, heartache, pain and in some cases poor health which can never be quantified or equated in monetary terms.
  2. The introduction of the Building Act in 1991 moved away from the prescriptive Model Building Bylaws (NZ Standard 1900 Series) adopted by Council’s throughout the country and moving to a performance based approach via the NZ Building Regulations, Code and Compliance Documents.
    This provided a much freer range for designers and architects to building design. The result in many cases was that the buildings did not perform as required by the NZ Building Code in forms of: Objective, Functional requirement and Performance!
    As a side issue would it not be better to revert to what worked in the past rather than a continual patch up job to the current NZ Building Code?
  3. New monolithic cladding systems were introduced into New Zealand that reflected Mediterranean styles. New Zealand however does not have Mediterranean weather and as a consequence the more aggressive wind and driven rain had a major impact on moisture ingress.
  4. Inadequate design features for New Zealand conditions aided water penetration. These “modern systems” of cladding being used outside of the manufacturer’s specification, coupled with lack of knowledge and a learning curve for tradespersons aid moisture ingress.
  5. In 2004 a requirement for monolithic claddings to have a cavity installed directly under the exterior cladding which became a belt and braces approach. It is noted that the cavity system is also required for other types of wall cladding where the design and or location of the building is considered a “risk”. The cavity acts as a wind pressure break and drain. It is open to the outside should water pass through the cladding.

The Cladding.

The monolithic cladding today is a composite material making up part of an element of a building. Normally this is considered the wall cladding.

  1. Texture coated fiber cement.
    The plaster/paint finishing is over a fiber cement sheet board substrate.
  2. EIFS: Exterior Insulation and Finish Systems.
    The plaster/paint system is over expanded polystyrene.
  3. Stucco.
    Sand and cement plaster applied normally in two coats over expanded metal lathing fixed to timber frame of fixed to treated plywood as a base. The plaster is often finished with a textured surface.

Identifying Maintenance Issues.

Regular maintenance may show up cracks in the surface. If sighted, then these are the start of a possible nightmare.

Is there a problem? or Do we just have a perceived problem?
Is it perceived? – NO it is very real.

First step is determining if there are cracks in the monolithic cladding then the best way to tackle the problem is to identify the cause, identify any resultant damage, remediate and resolve it.

Remember cracks are a result of movement. This movement is often referred to as “Stress”, the result of the movement.

What has caused the movement should next be considered and this can be answered often by the locations of the cracks.

If the crack is typically vertical; this would indicate that the joint beneath an opening and is vertical, 90 degrees then the sheet joint would appear to be inadequately fixed and or reinforced. The bracing around and to the opening could be suspect with the result of any flexing. If a sealant has been used this should be checked for any failure of side adherence to the sheets. Check also the durability period that the sealant has and replace if this period has or is near to expiring.

May16 01
Clearly visible sheet joints that have moved and cracked.

The background material that the monolithic cladding is fixed to would have a different coefficient of expansion, causing movement under heat (especially if painted a dark colour), wetness etc. Expansion/contraction joints should be designed to accommodate this movement.

Cladding that is too close to the ground can act as a “wick” and transport the moisture into the framing. Remove any built up garden soil!

May16 02b
Moisture absorbed into the cladding from the ground.

Inadequate/poorly designed flashings around openings. The flashings are too short and do not adequately cover the materials they are designed to protect. Construction Sealants are sometimes used as the flashing. This is a totally improper use of a construction sealant.

May16 03
Moisture absorbed from the ground and aggravated by impact and vibration of opening and closing of the door.

Cracks that are 45 degrees are often the result of poor bracing in the framed wall behind. Looking inside the house for similar indicators would indicate this to be the case.

May16 04

May16 05

 

How deep is the crack? If it is only a surface crack this could be the result of a poorly applied finish. In one particular case the applied finish had been watered down causing shrinkage cracks to result!

Is there any correlation with moisture readings taken on the inside with the cracks in the cladding?
All of these observations have been gleaned from many inspections. If there has been NO maintenance carried out on the monolithic cladding there will be problems. They can be small problems now but they will grow into bigger ones.

May16 06

Cavity beneath the monolithic cladding visible; acting as a drain.

Any questions please feel free to give me a ring or email me.

Regards.

Jim Bowler. FNZIOB.

 

Next edition we will look briefly at:
Weatherboards; Fiber cement, Hadiplank. Timber; both Cedar and Radiata pine bevel back and rusticated, Macracarpa, Plastic Palliside, Linea weather board,

All Buildsure Associates newsletters and content are an expressed opinion.

Note 1. In Isaacs/Bowler/Duff chapter “Finding faults in residential buildings” as part of the Building Pathology Volume 7 series. (copy available on request)

Note 2. Building Act 2004, 4. Principles to be applied in performing functions or duties, or exercising powers, under this Act. (2) (a) (ii) & (iii).

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