Product Product Invasive Test (Weathertightness) (Durability)Moisture detection units suitable for invasive testing weathertightness of homes.
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Invasive Test

Invasive test conducted through the skirting board and GIB to test the condition of the bottom plate.

This test recovered brown rot. The UTKD has been completely destroyed by decay.

The skirting board and carpet show no signs of dampness or damage and the scan reading was dry at 156 (Surveymaster scan readings below 180 are dry). This is because the framing had decayed to such an extent the wood fibres could no longer retain moisture. No scan meter or thermal image camera would discover this.

The crack in the GIB is down a sheet joint emanating from the corner of a window. GIB cracks above and below windows are common in two story homes. Those with concrete tiles experience greater movement as they are top heavy. Movement can also be caused by drying shrinkage, wind/vibration and settlement. In this case it would have been expansion and contraction from leakage as framing would get wet and expand, then in summer dry out and shrink back slowly growing the crack.

Demonstrates the importance of invasive tests.


 
Item All about Invasive Testing Folder
Document 02 Reading Moisture with Mdu Probe adaptor and industry meter.JPG
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Moisture Content Readings using a Mdu Probe
Moisture detection units or Mdu for short are designed to take accurate moisture content readings of framing hidden behind walls. By plugging a Mdu Probe adaptor into a standard industry meter set on resistance mode you get the exact moisture content of the framing. Just touch the adaptor against the two pins located in the Mdu cap.

The Mdu Probe is permanent and stays in the wall so future readings can be taken during the buildings life. This way owners get ongoing invasive tests without opening walls every time they want to know what is going on inside. If the moisture readings change owners know they have a leak so maintenance can be done.

 
Document Dry decayed framing behind newly painted walls
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Invasive tests reveal the facts.
Moisture detection became engaged to invasively test this property following a building report recommendation. The intended purchaser requested the entire building be tested as part of due diligence, not just the few recommended locations.

MDC invasively tested this location because it was under a high weathertightness risk roof scupper and negatively sloping soffit. The invasive test revealed no timber to extract. The wall was then opened. The bottom plate and chip board floor were completely rotted away.

The invasive tests were done in summer. All framing was found to be dry. Decayed framing in dry walls get missed in builders reports using moisture meters set on non-resistance scan or seek settings and by Thermal camera images.

Following the invasive test results our inspection found the issue was the negatively sloping soffit flashing had been fitted with its lap the wrong way. Over the years it had been repeatedly sealed at each re-paint. This disguised the issue and prevented a visual inspection discovering it. Each attempt at resealing may have worked for a period but then failed as walls dried and shrunk back. Between the maintenance cycles the framing got wet and rotted.

Below this image the ground level wall framing was much worse. Four studs wide had rotted away including the support studs for the steel beam (red in the bottom of the picture) leaving it unsupported.

Building inspectors must remain cautious so (should) write conservative reports when they see new sealing and painting. They just don't know if the painting was to disguise cracks and defects in sealants or part of normal maintenance. Maintenance may temporarily stop leaks but does not undo decay.
 
Document Invasive Test Framing Samples show importance of Boron treatment
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Invasive test timber framing samples taken from different era homes highlight the importance of boron treatments.

Both invasive tests were taken following recommendations in a builders report.

The left image door sill liner had rotted away which was visually noticeable and had a high scan indicating ongoing leakage. The rot was so bad it had a fruiting body growing on the paintwork. The sample collected by the invasive test is shown in the foreground. It is in excellent condition and tested strong for boron which has protected the wood and kept it durable. The home was built in 1986 when framing was required to be treated with Boron to 0.8%BAE (Boric Acid Equivalent) Hazard Class C8 protection against all wood destroying pests including insects, decay and termites.

The sample on the right was taken during another invasive test from a similar door sill liner that scanned wet but had no visual signs of problems. The recommendation was sound as the framing had become dust from brown rot. This house was built in 2000 with untreated timber.

Time was the difference for the door sill liner but not the framing. The difference that saved the 1986 home was the protection the 0.8%BAE treatment provided.
Document Invasive Test Framing Samples
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Timber framing samples taken during an invasive test clearly show weathertightness problems

Samples of framing removed from inside house walls during an invasive test.

Sample on the left is in excellent condition so durable and unaffected by moisture.

Sample on the right is decayed as it has obviously been wet for prolonged periods. It will need replacing.

The GIB linings, skirting board and carpets where the sample on the right was extracted had no visual signs of dampness or damage. The inspector found an elevated scan reading below a suspect window flashing so recommended invasive testing this location.

Obviously finding serious decay will affect a buyers interest in the purchase or the purchase price.
 
Document Uncertainty requires testing
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Invasive Test Procedure using Mdu Probes

Owners must give permission before these tests can be conducted.

Invasive Tests are required to assess the Weathertightness of a building whether the roof, gutters, claddings, windows, flashings, decks and ground lines are effective in preventing rain water from entering the home or its structure.

Conducted by a professional with weathertightness expertise.
Normally to a prescribed procedure so as to not damage the building.
Normally recommended during a building inspection or when a building inspection report red flags areas of uncertainty.

Reason for Invasive Testing: Building inspectors raise flags when they identify weathertightness detailing which is abnormal and have a history of failure. Their concern is visual inspections do not involve cutting or drilling to find out if the building is or has suffered from rainwater entry affecting the home or its structure. In some cases, damage is obvious; carpets may be wet, ceilings with stains and walls get cold and spongy.  Sometimes mould may be found. These are the visual surface consequences. But when the inspector raises an alert they are worried that behind the surface the insulation, wall framing and support mechanisms may be wet, or have been wet. The consequence could be decayed framing, mould, weakened bracing, loss of structural support, or rust. Insulation values may be lost. Toxic mould can grow. The inspector cannot determine whether the risk is real or serious by visual or scanning or thermal images cameras.

For example take the uncertainties with this portion of this home. The roof flashings may be recent so damage could already have occurred, or there may be no saddle flashing so it leaks inside. The window head flashing is embedded into the plaster so could be leaking down the wall. The side windows are stepped so the sill flashing may be leaking. The sill flashing may not have upturns so allowing water in. The pagoda penetrates the cladding in multiple locations which could be allowing water in. The plaster is embedded into the ground and water may be wicking up and wetting the framing. The framing may not be treated against decay so damaged and rotten. No-one cal tell for certain until we install Mdu Probes or remove the cladding. That is your choice.


Moisture detection specialises in invasive testing using the Mdu probes which are designed to take accurate moisture content readings of framing hidden behind walls. By plugging a Mdu Probe adapter into a standard industry meter set on resistance mode you get the exact moisture content of the framing. Just touch the adaptor against the two pins located in the Mdu cap.

The Mdu Probe is permanent and stays in the wall so future readings can be taken during the buildings life. This way owners get ongoing evidence without opening walls every time they want to know what is going on inside. If the moisture readings change owners know they have a leak so maintenance can be done.

The Mdu Probe system does not involve damaging the claddings or internal linings. The invasive test is done through the skirting board (normally). The only thing visible is the small cap the size of a shirt button.

Owners must give permission for this test.
Invasive Test:
Weathertightness test of a building to determine if the roof, gutters, claddings, windows, flashings, decks and ground lines are effective in preventing rain water from entering the home or its structure.
Normally conducted by a professional with weathertightness expertise.
Normally to a prescribed procedure so as to not damage the building.
Normally recommended during a building inspection

Reason for Invasive Testing: Building inspectors raise flags when they identify weathertightness detailing which have a history of failure. Their concern is visual inspections do not involve cutting or drilling to find out if the building could be suffering from rainwater entry affecting the home or its structure. In some cases, damage is obvious; carpets may be wet, ceilings with stains and walls get cold and spongy.  Sometimes mould may be found. These are the visual surface consequences. But the inspector is raising an alert because they are worried that behind the surface the insulation, wall framing and support mechanisms may be wet, or have been wet. The consequence could be decayed framing or rust. Insulation values may be lost. Toxic mould can grow. It could be serious.

The warnings by a building inspector may be the first you hear about this. They carry equipment like surface scanners and Thermal Image cameras. These are designed to find differences in density which could mean wet walls. Worse still the framing could be decayed and the structure is in trouble and expensive to repair. The recommendation to Invasive Test is to find out whether there 'could be a consequence' caused by the weathertightness detailing laying hidden between the walls.
 
The prime information gathered during Invasive Tests are the condition of the framing, the treatment level and the moisture contents.


Invasive Test: Outcomes
Normally conducted by a person with Weathertightness experience.
Bad results are decayed framing.
Good results are framing in good condition.
Interpreting in between results needs expertise.

Invasive Testing is the reverse engineering of surface inspections. The objective is to get sufficient samples of the underlying structure hidden behind the building walls to draw conclusions about the damage, cause of damage and likely outcomes for owners.
 
A good starting point is the condition of the samples extracted during Invasive Tests equals the sum total of all the rainwater exposures the timber framing has had since it was milled from the Forrest, erected as framing and subject to inservice conditions since enclosed during construction.
 
Obviously decayed framing means defects have allowed water in, over time, to cause damage. It could also mean the framing was not adequately treated to be used in that wall.  
 
Results may be:
  • Timber in good condition and dry. Nothing to worry about.
  • Timber in good condition but wet. Means current leaks need repairs but structure unaffected. Could be because the framing has been treated to a level to prevent decay. It could mean a previous owner has already discovered the leak and had it repaired and replaced decayed framing, but the leak repair has failed or the wrong detail was deemed responsible. Further investigation required.
  • Timber is decayed but dry. It could be a summer test so currently dry. It could mean an owner has discovered the leak and had it fixed but left behind decayed framing. The structure could be compromised. You could be left with the legacy of damage.
  • Timber is decayed and wet. This means the leak is ongoing and the framing has become damaged. The framing was inadequately treated against decay, or not treated at all. Substantial repairs are required to both the framing and the claddings. It is advisable to extend the Invasive Testing to more similar locations around the house in case this is systemic.

There is a lot of scope between decayed framing and good condition framing. Framing may show evidence of early decay. Moisture contents may be marginal for decay. Framing may be treated to resist decay but for short periods. This is where a person with weathertightness experience is important. Owners may have many options.
 
Invasive Test: Causes of wetting
Wetting is the physical change when absorbent materials absorb liquid.  
There are three main wetting mechanisms
  •  Liquid form: Water enters a crack or gap and enters the building fabric in liquid form and runs down the walls under gravity slowly becoming absorbed into anything it contacts with that is porous. This is called the ‘leak pathway’ and is generally given the from of a Christmas Tree shape, broader at the base and conical at the top where the leak is. This wets mainly the framing at the leak entry point, horizontal obstructions like bottom plates and boundary joists, absorbent claddings like Harditex and Stucco, the insulation and Chip Board flooring.
  • Wicking mechanisms: Wicking is the transport mechanism moving water from one porous material to another. Water wicks through and along porous materials like Harditex, Stucco, Chip Board flooring, GIB boards and framing until it becomes saturated. Does not need a gap to occur. An example is putting the tip of paper into a glass of water.
  • Vapour and Humidity: Wet materials inside walls will remain in an active state of trying to dry out. This process of evaporation is where water absorbed in materials evaporates into the air within the walls increasing its humidity which then redistributes the suspended water to surrounding drier materials until moisture contents reach equilibrium. This causes all materials to gain moisture. This often creates a vapour pressure which drives humidity beyond the ‘leak pathway’.

Invasive Tests are needed to determine which or all of the principals are operating and what options are available to reduce them to stop wetting and damage.