FAQ’s – RotStop and Moisture Detection Probes

Here are the most common questions that we are asked about Moisture Detection Probes and RotStop timber treatment. Please contact us if you have any further questions.

RotStop – Kills Rot and Makes Untreated Timber Decay Resistant

Q. What is RotStop?

RotStop is a unique timber preservative based mainly on boron salts – which have been used to protect timber in NZ homes for over 70 years.  Boron isn’t enough on its own to kill off all existing decay so we add extra fungicides and moldicides to control anything that might be in your house.  To help the treatment foam up and penetrate deep into your timber, we add special surfactants.

Q: How does RotStop kill rot fungi?

A: RotStop taints the water and food sources used by the rot fungi. As the fungi consumes this food source, the boron (basically a salt) destroys the fungi digestion system.

Q: Is RotStop safe for Humans?

A: Yes. In its liquid form during injection it can cause irritation if splashed into your eyes. RotStop should not be consumed. When the walls dry the active Boron represents approximately 1.5% by weight of the timber – where it is safe from humans.

Q: Why do rot fungi grow in the timber framing in walls?

A: Because when wet timber is left wet it rots. Rot growth is dependent on whether the framing is untreated or undertreated (eg H1). Even treated timber can rot if wet long enough. Fungi require 5 things to enable growth:

Spores:- Spores must be present for germination to occur and growth to begin.
Water:- Water must be inside the timber framing (as moisture content – mc). Liquid water is required for germination to take place then as long as the relative humidity remains above 80% the wood stays wet and rot keeps growing.
Food:- Wood contains cellulose – it’s a building block. In some instances lignin is consumed as well.
Air:- Fungi are nitrogen fixers so need air – 80% of which is nitrogen.
Warmth:- Fungi like temperatures between 10 – 40 deg C. Rot growth can totally destroy juvenile untreated pine timber framing in a matter of a few months at 30% moisture content, 30 deg C.

Q: How is RotStop injected into the house?

A: RotStop is injected, as a foam, into the wall cavities between the studs and the nogs.  Multiple injections are carried out to saturate the timber fibres and follow any leak paths to where there may be existing decay.  A reservoir of concentrated boron is left in the timber to protect against future leaks.

Q: What if our home leaks again in the future. Will RotStop still work?

A: Yes. RotStop is held within the trachea deep inside the timber and will keep working forever. RotStop is water soluble so whenever the wood framing becomes wetted it will again dissolve tainting both the food and water sources essential for fungi to germinate and grow.

If a new leak goes undetected for too long (this is why moisture monitoring is important) RotStop can leach out, lowering its potency against killing rot fungi. RotStop can be re-injected if RotStop concentrations fall – provided the leak is stopped no damage should be possible.

Q: How long does RotStop last?

A: Forever as long as it is not washed out by serious leaks – which is almost impossible throughout the cross section of wood.

Q: If RotStop injection is not 100% complete does it matter and will it mean parts of the timber are unprotected?

A: No it does not matter. The object of RotStop is to protect (what we term) the leak pathways. Leaks allow unwanted water to enter behind the cladding and into the timber framing. When a leak happens, water can get behind the cladding and be transported via gravity and absorbency pathways to much larger areas. This also occurs with RotStop during injection.

What is important is that if a leak occurs in the future, water will pass the RotStop injection points and dissolve some of the boron thus tainting the water as it spreads, killing all rot fungi in the process. We target and deposit concentrated RotStop in the leak pathways where it will be useful as the dwelling ages.

Q: Can RotStop fix already decayed timber?

A: No. Before RotStopping a house, we measure the moisture content, and decay level of your timber. In some instances timber may be so decayed and if it is at structural locations we recommend replacement. We will advise this in the normal process.

Q: What areas of the building benefit most from RotStop?

A: All areas found to be affected by Rot Fungi and historical positions known for leaks and product failures.  The entire house benefit from RotStop but typically the complete bottom plate, beneath windows, decks, known leaks or other vulnerable architectural features are recommended.

Q: How long does RotStop Injection take?

A: Normally 3 days for selected small areas. Larger houses could take 5 – 7 days depending on what parts are being treated.

Q: Do I get a RotStop treatment warranty?

A: Yes.

Q: Can we stay in the house while RotStop is being injected?

A: Yes. RotStop is normally injected through small holes in the exterior cladding with minimal disruption to the occupant. We will need access inside your house for power etc and in some circumstances, certain injections through the interior gib board may be necessary. Some owners have found RotStop during injection has a sweet smell – but none have suggested it is unacceptable to live with. Once injected the smell disappears.

Q: What happens to the RotStop holes?

A: We will plaster over these once the job is complete. We can quote to touch up paint or you can arrange to do this yourself.

Q: How does RotStop treatment compare to Building Standards treatment requirements?

A: Current standards have recently returned to pre 1987 treatment levels of 0.4% boron active equivalent. This means boron as a percentage by weight of timber is 0.4%. RotStop’s target is 1.5% which is approximately 4 times that level Once fungi have germinated and growth has begun boron concentrations must be above 1% to kill them. RotStop concentrations are intentionally stronger than NZS 3602 and strong enough to eradicate growing rot fungi. RotStop is an essential treatment process to protect untreated and undertreated framing that has become affected by rot or may be affected during the buildings lifetime.  All homes with low levels of boron (or none at all) have no protection against rot fungi. RotStop is therefore considered the most important step in repairing and protecting homes that are or may be leaking.

Q: If rot fungi is well established and deep into the wood can RotStop still work?

A: Yes. Because RotStop is taken deep inside the wood where fungi get their food source from. As the wood becomes tainted and toxic the fungi dies. Interestingly most buildings dry out in the summer when rainfall that cause leaks is minimal. As winter approaches, water introduced through leaks becomes contaminated with RotStop and further assists in killing the fungi.

Q: Is all my wood fully impregnated with RotStop?

A: No. It does not need to be. Provided RotStop is positioned along leak pathways in a concentrated form any water that does get in will dissolve the RotStop and distribute the boron to any wetted timber.

Q: Will RotStop also kill borer?

A: Yes. RotStop concentrations are 40 times that required to control borer.

Moisture Detection Probes and System – Prove your house does not leak and find any problems early

Q: Where do you put the probes?

A: The probes are normally installed in the skirting boards at areas where we know that any moisture from leaks might show up, e.g. under the corners of windows, door entrances, under complex gutters and roof/wall junctions.

Q: How many probes will I need?

A: That depends on the size of your house, its complexity and your requirements. For a basic pre-purchase inspection installation, there would be at least 20 probes however for a large multilevel house, where the owner wants to have total confidence that their house is safe, there could be 80 or more probes.

Q: What is included when I have probes installed?

A: The probe installation scope is comprehensive and includes:

  • Loading your house plans onto our database
  • Extracting 2 x timber samples at each probe installation
  • Inspection under a microscope and grade samples for levels of decay
  • Laboratory analysis to determine if the timber is treated, the type of treatment and the strength of the treatment.
  • Testing and reporting on the strength of the timber framing at each location
  • Installing the moisture probes
  • Initial moisture readings of the probes
  •  Initial investigation and recommendations for any leaks or timber damage found
  • All data uploaded and stored on your house page on our servers
  • All timber samples retained for future reference or comparison

Q: How much does all of that cost?

A: It does depend on how many probes you have installed, however the cost is very reasonable, starting at around $1,000 plus GST for a basic (20 probe) installation.

Q: How long does the installation take?

A: A basic installation usually takes about half a day but larger, more complex houses may take up to two days. 

Q: How do the probes get read and how often?

A: The probes are read by our technician with a special moisture meter. Every reading is uploaded to your house webpage. We recommend reading every 6 months to locate leaks before they cause damage.

Q: How can probes at floor level detect leaks higher up in the house?

A: We have done extensive research which proves that leaks travel down through the framing timber and water collects in the bottom plate, which is where we place the probes.

Q: What happens if the probes find leaks?

A: MDC can recommend steps to stop the leak, and often carry out the repair themselves (for basic repairs), or recommend a contractor. When the probes are read again, they will show if the repairs have been successful.

Q: Will the probes look obvious?

A: No, they just look like small buttons attached to the skirting boards. We even have brown coloured ones in case your skirting boards are just stained or varnished.

Q: Can I have the probes removed?

A: Yes. If you ever want to remove them, you can just pull them out and fill the holes – but why would you ever want to stop finding out how to maintain your biggest asset?

Q: Can anyone else install moisture detection probes?

A: No. The probes were invented by us and are protected by a patent. We install them to protect the investment that New Zealand homeowners have in their houses

Proven solution for stopping decay and protecting timber in monolithic clad buildings

  • Identify and treat leaks and rot without recladding
  • Safe, proven post-treatment for treated and undertreated timber
  • Low cost alternative to house recladding for most monolithic houses
  • Scientifically tested and approved
  • Protects against all known fungi, decay and borer
  • Fast, non-disruptive and discrete
  • RotStop Certificate to help sell your house
  • Suitable for all monolithic clad or leaky buildings: apartments and commercial properties

“What You Absolutely Must Know About Owning a Plaster Clad House” – the essential property owners report

” I was shocked to learn just how the leaky home crisis happened but then relieved that Moisture Detection offer a pretty easy way to get my home sorted out”

  • Moisture Detection Probes

    Installed discretely to measure and monitor the actual moisture in your walls – and find any leaks

  • Timber Testing

    Measures actual timber treatment, level of decay and remaining strength

  • Targeted Repairs to Stop Leaks

    Identify and repair problem flashings, windows etc to stop leakage

  • Rotstop Treatment

    A proprietary and proven process to treat all timber quickly and safely. This kills rot and stops further timber damage. Timber resilience to rot is increased.

  • Regular Monitoring

    Low cost regular monitoring to ensure your house stays dry

  • Pre-Inspection Proof Your House

    Your complete house condition report proves that your house does not leak, is not rotten and is fully maintained

  • Permanent On-Line Data Base

    All of your inspection and maintenance records are stored on-line