London 020 7060 6593 & Exeter 01392 555 432

Timber Decay

Experts in timber decay & defect assessments

We investigate the condition of timber components, delivering this service with extensive practical experience and in-depth relevant academic knowledge of timber building conservation, timber science and its strength in-use.

Harper Building Diagnostics specialise in the assessment and rehabilitation of timber defects, assessing the condition of timbers, investigating the severity of any damage identified, establishing if the issues are historic or ongoing problems – as historic damage may not require any intervention, unless it is thought to be structurally significant.

Fact: ‘dry’ timbers are not at risk from fungal or insect decay

It therefore becomes essential to investigate how any decaying timbers have become damp.

Once investigations are concluded, we follow a holistic, conservation-minded approach to resolving defects identified, concentrating on correcting the causes, rather than promoting a reliance on chemical treatments and product-lead remedies. Our reports give the client an objective and informed assessment of the structural condition of the timbers, enabling informed decisions to be made.

Timber Defects

Non-destructive techniques - minimising the loss of material, disruption and cost.

We use a range of non-destructive techniques to quickly evaluate the sub-surface condition of timbers. Microdrill and ultrasonic decay detection equipment are used to help locate and measure the extent of decay beneath the surface of timber components.The microdrill is extremely adept at assessing sections of timber imbedded in walls or behind plaster finishes.

This conservation-minded approach is used to investigate the severity of damage caused by dry rot, death watch beetle and other decaying organisms.

We also utilise a range of small diameter endoscopes in order to inspect behind panelling, ceilings and floor voids , so to minimise disruption and exposure works.

Please call to discuss our range of non-destructive techniques and minimally invasive methods of investigating and quantifying the extent and severity of building defects.

Not sure what level of equipment is required for your project?

No matter what diagnostic equipment and testing we use, it is all included in our fee,

no hidden extra’s!

Microdrill Investigations

We utilise Resistograph microdrills for the assessment and detection of sub-surface decay and defects in timber, which are extremely adept at assessing decay in the ends of timbers embedded in masonry.
A 1.5 mm needle penetrates the timber at a constant speed and measures the resistance of the timber against the needle, recording the exact location and extent of any decay identified.

Surface holes are discrete, refilled automatically with the extraction of the needle, and resemble a beetle flight hole.
We operate 2 microdrill models,  a 300mm which excels at assessing timbers in tight spaces, and a 600mm model which is essential for assessing large dimensional timber components.

Ultrasonic Decay Detection

We use Ultrasonic Decay Detection (U.D.D) equipment to detect decay beneath the surface of timber. An ultrasound pulse is transmitted through the subject timber and the time it takes to cross the section is recorded. The signal travels faster through ‘sound’ timber, and therefore delays outside the expected parameters provide a strong indication of the presence of cross-sectional decay and other defects. Suspect areas identified by the UDD are quantitively assessed with microdrill instrumentation.

Large numbers of timbers can be quickly and cost-effectively assessed using this non-destructive technique.

Do you need to know the sub-surface condition of timbers on your project?

The micro-drill/probe & U.D.D are currently the most accurate, sensitive & cost-effective way of assessing sub-surface timber decay.

Measuring moisture content

It is vital to establish the moisture content of timber; moisture levels reflect localised environmental conditions, and this information assists in establishing the root cause of decay and the level of risk from bio-deterioration.

Borescope & inspection cameras

We use borescopes and video inspection cameras to look behind panelling, below suspended timber floors and into ceiling voids, allowing a thorough assessment with the minimal of disruption and loss of material.

In-situ visual strength grading of temperate hardwoods (to BS5756)

In-situ visual strength grading is a method of determining the potential load bearing capacity of an individual length of timber.

Designers and engineers need to know that new or retained structural timbers will perform as envisaged under working loads and stresses.
The performance of a structural timber component is determined by its species, its dimensions, and its natural growth characteristics etc.
It is those growth characteristics such as knot area ratio, slope of grain, fissures, insect and fungal defects, that are assessed by visual strength grading, and will determine the strength classification assigned to each piece of timber.

We grade timbers that are destined for new buildings and extensions, and for the repair of historic buildings.
Changes in how old and historic buildings are used can place greater loadings and stresses on structural timbers.
In-situ visual strength grading will help establish if existing timbers remain adequate for their projected loading, or if they will require strengthening works.

Awkward access?

All assessments can be undertaken at height using rope access and powered access solutions, call to discuss your project requirements

Environmental controls - minimising the use of chemical treatments.

Chemical treatments and other product-lead interventions have a limited ability to resolve dampness and decay over a sustained period, with these practices often detrimental to the fabric of the building and potentially harmful to your health.

Because we know moisture causes timber decay and damp problems, we are acutely aware that controlling excess moisture is fundamental to the longterm success of any repair. Our environmental approach will minimise the use of chemical preservatives.
We view buildings and structures holistically, investigating the underlying issues that have facilitated the defects. Our recommendations present a full range of options that consider the most proportionate, appropriate and cost-effective solution specific to your project.

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Covering the UK from both the Exeter and London offices

London Office:

Harper Suite 1 Crutchfield Lane, Walton-on-Thames, Surrey. KT12 2QY
Phone: 020 7060 6593

Exeter Office:

The Office, The Old Shippen, Upton, Clyst St Lawrence
Cullompton, Devon. EX15 2NP

Phone: 01392 555 432