Timber Decay Timber Decay Sporophores of the dry rot fungus; Serpula lacrymans affecting floor joists Building materials are decayed by the effects of adverse environmental conditions and the extent of damage depends on both the materials and the conditions. Among the most vulnerable materials are timber, paint, textiles and paper. Timber remains one of the most useful in a world of diminishing resources and is a major component in most historic buildings. It has many positive structural and aesthetic properties as well as being an energy-efficient and renewable resource. However, timber provides specialised ecological niches and many organisms have evolved to use it as a food. The most common and destructive to timber are dry rot, wet rot, common furniture beetle, and death watch beetle. Orthodox remedial treatments often entail the loss of irreplaceable decorative finishes, floors and ceilings. Furthermore, treatment of the infestations with insecticidal fungicidal chemicals is not only expensive, inconvenient, hazardous to the operatives and occupants but also environmentally unacceptable and usually unnecessary. Environmental control and preventative maintenance provide an alternative, less destructive solution, and remain the most widely used methods for preventing biological decay.

BIOLOGICAL DECAY MECHANISMS Biodeterioration of materials was defined by Hueck in 1968 as 'any undesirable change in the properties of material of economic importance brought about by the activities of living organisms'. A wide range of materials are subject to microbiological deterioration, which are caused by a broad spectrum of micro-organisms. Beetles responsible for the decay of timber principally include woodworm (Anobium punctatum), death watch beetle (Xestobium rufovillosum), powder post beetle (Lyctus spp), and house longhorn beetle (Hylotrapes bajulus). It is their larvae which cause most damage as they bore through the wood, feeding off it and causing damage to the structure and strength of the timber. Decay fungi are capable of enzymatically degrading complex cellulosic materials, such as wood, into simple digestible products. The decay of wood cells by these fungi results in the loss of weight and strength of the wood. There are two main types of wood-rotting fungi found in buildings; wet rot and dry rot (see Table 2). The principal environmental factors favouring the biodeterioration of building materials are temperature, humidity and a lack of ventilation.

Moisture may be contributed by penetrating or rising damp; condensation; building defects and disasters such as leaks; and from construction moisture introduced in mortar, concrete and plaster for example. ENVIRONMENTAL CONTROL - THE GREENER APPROACH Environmental control relies on controlling the cause of the problem by controlling the environment. It is designed to ensure the future health of the building and its occupants by avoiding the unnecessary use of potentially hazardous and environmentally damaging chemical pesticides where possible and their consequential legal and management complications. Eradication of dry rot spores or insect pests in an historic building and its contents is in practice, impossible. The volumes of chemicals necessary and the toxicity required would be damaging both for the buildings and all its occupants. Where chemical treatment cannot be avoided materials and techniques should be used which have minimum adverse environmental effect. By reducing the need to expose and cut out infected material, environmental control also reduces damage to the fabric and the finishes of a building. Where an historic building is concerned, this is particularly important, and the specification should ensure maximum conservation of existing materials to maintain the historic integrity of the fabric, as well as to avoid unnecessary expenditure. Its success depends on a thorough investigation of cause and effect.

Through a methodical approach such as this, it is possible to decrease the cost of remedial timber works significantly or in some cases eliminate it altogether. First the building should be thoroughly inspected using non-destructive techniques to locate and identify all the significant decay organisms within it. In cases of actual or suspected problems of woodrot or wood boring insects in buildings, investigation should be by an independent specialist consultant, architect or surveyor to establish the cause and extent of the damp and timber decay, including the potential risk to the health of occupants before specification or remedial work. Correct identification of the fungi and insect material is important as not all fungi are equally destructive. Some rots are present in timber when it is cut or are acquired in storage. Fungal material may also be dead or dormant, the product of conditions now past. Having identified the nature of decay, the environmental conditions which are required to support it should be considered (see Table 1). Only then will it be possible to devise a scheme to deal with the problem. The aim of remedial building works is to control the timber decay, to prevent further decay and to correct any significant building defects resulting in conditions of high moisture content or poor ventilation of timber.

In particular, it is important to reduce sub-surface moisture content of all timber to below 16-18 per cent. Timber should be isolated from damp masonry by air space or damp proof membrane, and free air movement should be allowed around timber in walls, roofs and suspended floors. All other sources of water should also be eliminated, such as overflowing gutters, leaking plumbing, condensation and rising or penetrating damp. Humidity in voids should not exceed an average relative humidity of 65 per cent. In addition, all active fungal material should be removed together with all rotten wood, and the structural strength of the remaining timber and fabric construction should be assessed to determine whether reinforcement or renewal is required. In the case of insect infestation, measures should also be introduced to avoid recontamination. Dirt, dust and builders' rubbish provide a haven for insects and fungi. Voids and cavities should be cleared and the areas cleaned with a vacuum cleaner to remove dust. A programme of building maintenance and monitoring may then be instigated to prevent any future problems.

Plaster fungi: Coprinus spp; Peziza spp; Pyronema spp Stain fungi: Cladosporium spp; Aureobasidium spp MONITORING SYSTEMS Remote monitoring systems can be very useful in increasing the efficiency and decreasing the cost of maintenance programmes. They can be especially useful for checking the moisture content of inaccessible timbers in roof spaces, behind decorative finishes and in walls. Sensors can be placed at all critical points after the investigation or after remedial building works. Areas can then be closed up and finishes reapplied; for example sensors may be placed in lintels, joist ends, valley gutter soles or in damp walls to monitor drying. It is important to use enough sensors and to place them with an understanding of the moisture distribution processes, because conditions can vary even in a small area. It is these local variations in conditions that produce the environmental niches which decay organisms exploit. If more than 30 sensors are deployed, taking the readings can become onerous and this may result in human error or negligence. In these situations automatic monitoring systems become desirable and a number of specialised systems have been developed. With larger systems the wiring of sensors can also become a problem.

For systems requiring 100 or more sensors, a computerised unit is used, working via a single four-core mains cable connecting up any number of nodes, each supporting four sensors. This system can be programmed to record and log data at regular intervals with alarm limits for each sensor. The data is then transmitted to a remote computer via a modem connected to a telephone line. Data from the system can then be analysed using CAD and programs for statistical interpretation. TIMBER MOISTURE MONITORING SENSORS The water content of building materials can be determined through a range of direct and indirect methods. Direct methods involve removal of a sample of the material to be tested which is weighed and then dried to determine its water content. This has the disadvantage of being destructive and it cannot be used for remote monitoring. Indirect methods are based on measurement of characteristics related to the moisture level in the testing material. These involve thermal conductance, electrical capacitance and resistivity. Measurement of a surrogate material in equilibrium with the first material is another method. The use of electrical resistance moisture meters provides a quick and relatively accurate method of determining the moisture content of wood if a knowledge of their limitations is taken into account.

Moisture meters measure the changes in resistance, due to changes in moisture content, between two electrodes placed in the timber. Increasing moisture content results in a reduction in electrical resistance. Miniature sensors are fabricated from hygroscopic material which has been calibrated to match the moisture content changes in timber. They are encased in a protective shell. The sensor is then inserted into a previously drilled hole to the required depth and the hole sealed. In most instances the sensor cable seals the hole to the outside. The sensor will fairly rapidly come into equilibrium with the atmosphere within the hole. Due to their small size the sensors can be inserted into the centre or ends of large dimension timbers allowing the best chance of detecting defects early. MASONRY MOISTURE MONITORING SYSTEMS Systems for use with masonry can be based on the direct measurement of the material's moisture content or by the use of a surrogate material which changes in moisture content in a similar way to the host material. This material may be of any hygroscopic type which, providing it has been calibrated correctly, can be used as the basis of a remote sensing system. The sensors are placed in the material to be tested at the required depth, or in an array and the hole sealed to the external atmosphere.

Sensors will come to equilibrium with the relative humidity within the cavity or drilled hole and hence with the surrounding material. Single sensors can be placed at varying depths but must be sealed within the area to be measured. A series of sensors individually sealed within the drilled hole can provide a profile of readings across the material. These can either be wired up and resistance measured remotely or can be removed, weighed and oven dried to calculate their water contents. Changes in the water content of masonry can be rapid when wetted so that it could provide an early warning of building defects leading to water penetration. However, drying down can take many weeks or years. The Building Conservation Directory, 1996 (where it appeared as 'Environmental Monitoring and Control') Author JAGJIT SINGH BSc MSc PhD CBiol MIBiol AIWSc FIRTS is currently Associate Director with Oscar Faber Consulting Engineers (St Albans) and is the head of Oscar Faber Heritage Conservation. He has over 15 years' experience in both academic research and industry.

He specialises in the study of the biodeterioration of building materials and associated environmental health problems Dryrot | Article about Dryrot by The Free Dictionary Dryrot | Article about Dryrot by The Free Dictionary Also found in: Dictionary , Thesaurus , Medical , Wikipedia . dry rot, fungus disease that attacks both softwood and hardwood timber. Destruction of the cellulose causes discoloration and eventual crumbling of the wood. This frequently results in the collapse of wooden structures such as house flooring, mine shafts, and ship hulls. Because the fungi require moisture for growth, dry rot occurs most often in places where the ventilation is poor or humidity is high or when the wood has been improperly seasoned. In the United States it is most frequently caused by a pore fungus (Poria incrassata) and by the dry-rot, or house, fungus (Merulis lacrymans). It may be prevented by application of creosote or other preservatives. Dry rot sometimes attacks standing conifers. The name is also used for other fungus diseases that attack the roots or stems of plants (see diseases of plants diseases of plants. Most plant diseases are caused by fungi, bacteria, and viruses.

Although the term disease is usually used only for the destruction of live plants, the action of dry rot and the rotting of harvested crops in storage or transport is similar to the rots ..... Click the link for more information. ). Dry rot A fungi that feeds on, and destroys, damp rather than wet timber. Most often found in damp, poorly ventilated under-floor spaces and roof areas. Causes timber to lose strength, develop cracks, and finally become so dry and powdery that it is easily crumbled. dry rot Diseases Of Timber Diseases Of Timber Description This section is from the book " Manual Instruction: Woodwork. The English Sloyd ", by S. Barter. Also available from Amazon: Manual Instruction: Woodwork . Diseases Of Timber The diseases to which living trees are liable do not properly concern us here, but inasmuch as wood may be, and not infrequently is, brought into the market in a more or less damaged condition from diseases which affected it previous to felling , it is perhaps worth while to say a little about two or three of the diseases of living trees.

The most common and destructive disease, in northern climates at any rate, and one which attacks the most widely-used timbers in this country, those of the conifers , is wet rot. This disease has been traced to various fungi by the brilliant and invaluable researches of Professor Hartig of Munich, who, with other distinguished German botanists, has done so much to enlarge our knowledge of timber trees and their proper management. I am immediately indebted for the notes given here, however, to the writings of Professor Marshall Ward, who has brought this subject in its true aspect before the English public. Wet rot is caused most frequently by a fungus which germinates in moist ground round the roots of a tree, and entering them, sends out a large number of long white filaments, which attack and feed first on the cambium cylinder, and next on the starch and other food materials in the cells of the medullary rays, ultimately sending a complete network of arms through every part of the heart-wood, and reducing it, by delignifying the walls of the tracheides, to a soft, moist, spongy mass, with no traces of the original properties of the wood.

Of course this attack, commencing as it does from the base of the tree, rapidly kills it. Timber which has been partially destroyed by this parasite can be distinguished by its reddish or purple tint in places, or if the disease be very advanced, by dull, yellow, soft patches with clear white spots, having a small black speck in the middle of each. It is rarely seen, however, as advanced as this. Another fungus which is somewhat similar in its action, inasmuch as it attacks the roots of trees, is the Agaricus Melleus. Its distinctive features are, that it is able, by long sinuous branches, to spread indefinitely to the roots of neighbouring trees not actually in contact. This fungus is very common in this country, and may be detected by its fructification on and near the roots of trees, in the autumn. These fructifications appear as toadstools of a yellowish colour, with rings round their necks. The visible effect of this disease is to give timber a bright yellow colour in places, in the midst of which are visible white patches. Beech is particularly affected by this disease.

The familiar clinging, felt-like substance, of a yellow to deep brown colour, frequently seen on oak and other trees is a very destructive form of fungus, which, from this felt-like mass, sends out feeding shoots into the wood, and destroys it somewhat in the same manner as the other parasites described. Fortunately this fungus is only able to penetrate the tree where it has been previously wounded by some other agency. This disease is readily detected by the white filaments running in all directions in the timber, or, if only slight, by the brown patches which will appear, making the wood quite powdery to the touch. Of course many other parasites attack trees, and rot is occasioned by old age in addition; but if, in selecting timber, care be taken to reject such as may have any of the faults referred to, good wood will generally be obtained. Foreign timber is not often seen in a very advanced state of decay, as it is usually not shipped by the timber merchants when found affected. After timber is felled it is still very liable to diseases, of an equally serious character to those of living trees.

One of the fungi which attacks cut timber is very liable to commence its ravages in any crack which the surface of the log may offer, even when yet in the forest, its effects being apparent, perhaps, only after months of storage in a timber yard. Streaks of brown or red colour, of moist, spongy nature, probably with patches of the white fungus itself, sometimes appear in boards, and are the result of this disease. Timber with this defect should never be accepted, as the fungus will spread and entirely spoil the whole of the wood, or any other sound timber with which it comes in contact. The exclusion by the woodman and the buyer of diseased living timber makes the defects already alluded to less frequently seen than would otherwise be the case. But a disease with which everyone is familiar, and to which even the soundest timber is liable, is the dry rot. This disease is due also to the ravages of a fungus which eats into and decomposes the wood. It can be readily discovered by the fine web of filaments running all over the surface of the wood, and, in cases of advanced disease, by felt-like patches on the surface of the timber.

The great preventive and cure of dry rot is a free circulation of air. A damp, still atmosphere, such as is found in cupboards and cellars, is very liable to produce rot. Even in these situations, if timber be thoroughly seasoned and quite dry before being used, and be kept dry, it is impervious to dry rot. The difficulty of keeping timber dry in spite of the exhalations from the earth in cellars and similar places is, however, usually found to be insuperable unless free ventilation is resorted to. Timber built into walls, like the ends of beams, is very liable to dry rot (really a very inappropriate name) because of the want of ventilation; and if the end of a beam projects through the wall, the moisture which is so necessary for the propagation of the disease is rapidly absorbed. One of the chief reasons for the dislike to sapwood evinced by tradesmen is its great liability to attack from dry rot, probably because its tissues contain more starch and other substances for the fungi to feed upon. Wood Rot | Old House Web Tweet William F. Lyon Many homeowners are familiar with wood damage caused by rot.

They see it in structural lumber, log homes, eaves, garage doors, exterior door trim, window casings and other wood used in construction. Current estimates show that replacement materials, needed to repair damage caused by rot alone, account for nearly 10 percent of U.S. annual wood production. Blame for this destruction is sometimes incorrectly placed on termites or other wood-destroying insects. However, there are no mud tunnels or mines in the wood such as seen with termite and other wood-destroying insects, nor is there any sawdust, which would be evident in the case of carpenter ant damage. The key to preventing rot is to control the wood's exposure to moisture and to employ an effective prevention and treatment program. Most wood decay fungi grow only on wood with a high moisture content, usually 20 percent or above. Green (unseasoned) lumber is a prime target for decay fungi. Identification There are two main classes of wood rot. In one type, the decayed area has a brown discoloration and a crumbly appearance.

It usually breaks up into variously-sized cubes, giving rise to the name "brown cubical rot." Another type of rot results in a white or yellow discoloration, with the decayed wood being "stringy" or "spongy." Although many decay fungi may grow for long periods without producing any external evidence of their presence, others produce "fruiting bodies" on the surface of decaying wood. Fruiting bodies are usually "crusts" or shelflike "brackets" which are a few inches or so in diameter. The fruiting body of Serpula lacrimans, e.g., is a rust-brown, crust-like structure on the wood surface. It has a waxy appearance, with shallow, net-like folds or "wrinkles." The fruiting body of Poria incrassata is also crust-like. It is white to light buff when initially formed, but becomes brown as it ages and dries out. Small pores can be seen in the crust when it is examined with a hand lens. Gleophyllum trabeum forms bracket-like fruiting bodies. The upper surface of the fruiting body is dull gray-brown and smooth.

The lower surface has elongate openings (pores) or split-like openings (gills). These fruiting bodies produce millions of tiny spores which may, in some cases, serve to spread the decay fungus to other areas. Also, surface molds, "mildews," and stain fungi are often found growing on the surface of damp wood and can be confused with decay fungi. Although these organisms may discolor the wood, they do not break down wood fibers and thus do not weaken its structure. However, these organisms indicate that moisture is present and that decay will likely proceed if a wood-rotting fungus becomes established in the wood. Life Cycle & Habits Decay fungi are living organisms which send minute threads called "hyphae" through damp wood, taking their food from the wood as they grow. Gradually, the wood is decomposed and its strength is lost. Such damage is often inconspicuous until its final stages, and in a few instances homeowners have suddenly found floors breaking through or doors falling from their hinges due to wood rot. When previously dry wood is placed in contact with moist soil, or in a location where it is subject to condensation (such as unventilated crawl space), it is likely that wood decay problems will occur.

Rain leaks, faulty plumbing and leaky downspouts also are common sources of moisture. In some instances, water can be transported to the site of decay through strands or "rhizomorphs" of the decay fungi. Water-transporting strands may extend for thirty or more feet across brick, concrete or similar materials. The wood decay fungus, Serpula lacrimans, has been known to transport water up three stories to an area where decay is occurring. Poria incrassata is also capable of transporting water long distances. However, these fungi are exceptions to the rule. Most wood-rotting fungi must have a direct supply of water at the site of decay. Thus the term "dry-rot," sometimes applied to decay in wood structures, is erroneous. Control Measures Prevention If the decay hazard is high, select the heartwood of decay-resistant species or use wood properly treated with a good preservative. Conifers from which decay-resistant lumber is produced include Pacific yew, juniper, redwood, baldcypress, and western red cedar. Durable hardwood species include osage orange, black locust, red mulberry, catalpa and black walnut. Build on a well-drained site.

Use proper grading to prevent water from seeping under the house. Install effective drain tile, roof overhang, gutters, and downspouts. Place no untreated wood within 18 inches of the ground. Provide adequate cross ventilation beneath buildings to eliminate dead air pockets. Install two square feet of opening for 25 linear feet of wall. Dense bushes or other plants should not be placed in front of these ventilators. Install a vapor barrier on the soil surface to cause soil moisture to condense on the barrier and return to the soil rather than condensing on the floor and above joists. Satisfactory barriers can be made by covering the soil with asphalt roofing paper or polyethylene sheets. Repair of Decayed Buildings First determine the source of moisture and remove it. If adequate ventilation and soil drainage are provided and all contacts of untreated wood with the soil or moist concrete or masonry are broken, decayed wood will dry out and further decay will be stopped. When making replacements, cut out at least one foot beyond the rotten area. Avoid placing new lumber in contact with old, decayed wood. Replacement lumber should be treated before installation. Remodel to provide more ventilation and better design rather than simply replacing decayed lumber.

Chemical Treatment Disodium octaborate tetrahydrate or sodium borate with brand names of Bora-Care(r), Guardian(r), Jecta(r), Shell-Guard(r), Tim-bor(r) and Impel(r) rods are labelled for protection and treatment of wood and wood-foam composite structural components against decay fungi and wood destroying insects. For example, remedial control of organisms attacking wood, apply a 15 percent or two applications of 10 percent aqueous solution of Tim-bor(r) 98 percent (1-lb/gallon solution) or Bora-Care(r) diluted 1:1 or 2:1 with water. The solution may be applied by brush or spray until the surface is thoroughly wetted (approximately five gallons per 1,000 square foot). An application may also be made by drilling, and then injecting the solution directly into the infested area. Inject a sufficient amount of solution to cause runoff from exit holes drilled into the infested wood.

Also one may apply Tim-bor(r) dust to infested wood by drill and injection directly into galleries (a passage or tunnel made in wood by an insect); or dust wood surfaces and wall voids at a rate of two to three pounds per 100 square foot. Tim-bor(r) is applied by licensed pesticide applicators or pest control operators. For product information, contact U.S. Borax Corporation, 1(800)9-TIM-BOR. Shell-Guard(r) and Guardian(r) are labeled for protection and treatment against decay fungi and wood destroying insects. These two products are formulated with propylene and polyethylene glycols, making them doubly safe to use. Since these products are borate based, the protection is permanent after application.Guardian(r) is the highest concentration available in a formulated borate product. It can be directly injected into holes to provide fast penetration into problem areas. Rapid diffusion is assured by the formulated carriers. Holes can be sealed to match the original finish of the wood. Shellguard(r) is a liquid, labeled for topical application. Because of its concentration, multiple applications are unnecessary. Like Guardian(r), one application is all that is required.

Both of these products are labeled for home use, and can be easily and safely applied by the homeowner. (For further information on either Shellguard(r) or Guardian(r), contact Perma-Chink Systems at 1-(800)-548-1231 or 1-(800)-548-3554. Another formulation known as Impel rods is molded from highly concentrated water-diffusible boron into a solid tube resembling glass in appearance. These rods are internationally recognized as an effective preservative and deterrent to rot. Unlike fumigants and sprayed or brushed on preservatives, Impel Rods are inserted through small holes strategically drilled into wood where signs of rot are evident or in high-risk, rot-prone areas. The holes are sealed and may be finished to match the wood's original appearance. Rods are odorless, EPA registered, do not stain wood and are available in various sizes to fit virtually any application from heavy timbers and posts to millwork and door frames. However, where damage threatens the structure integrity of wood, the wood should be replaced.

Whenever the moisture content of wood is high enough to sustain rot, Impel Rods(r) slowly dissolve, spreading the active borate protection into the area surrounding the rod. When the wood dries, the preservative remains in the wood. As the cycle is repeated, the preservative builds up as an effective deterrent to rot. (For further information, contact Nisus Corporation, 215 Dunavant Drive, Rockford, TN 37853 Telephone: 1-(800)-264-0870, Fax: (423)-577-5825). In the past, pentachlorophenol (Penta(r)) and copper naphthenate was used as a stop gap measure. (These chemicals had offensive smells and were not environmentally safe.) Now with a growing environmental concern, various formulations of sodium borate do not pose a serious threat. A key valve is the absence of offensive smells sometimes associated with other common treatment methods. Also, existing moisture in the wood enhances chemical penetration. This publication contains pesticide recommendations that are subject to change at any time. These recommendations are provided only as a guide.

It is always the pesticide applicator's responsibility, by law, to read and follow all current label directions for the specific pesticide being used. Due to constantly changing labels and product registration, some of the recommendations given in this writing may no longer be legal by the time you read them. If any information in these recommendations disagrees with the label, the recommendation must be disregarded. No endorsement is intended for products mentioned, nor is criticism meant for products not mentioned. The author, The Ohio State University and Ohio State University Extension assume no liability resulting from the use of these recommendations. This story originally published by Ohio State University Extension. THE BEAM GUY - Know Your Wood Rotting Fungi THE BEAM GUY Know Your Wood Rotting Fungi Know your Wood Rotting Fungi: Graham Roy Coleman. Remedial Technical Services When looking at wood rotting fungi which may be found in the average domestic environment, it is first essential to understand that WATER IS REQUIRED TO INITIATE AND SUSTAIN ROT. So whilst there is some importance to be able to distingush between dry rot , Serpula lacrymans, and the rest (wet rots), they have ALL been caused by excess water in timber!

And the basic control is to eliminate the water causing the rot - dry wood doesn't rot!! The first practical observation which should be made is to determine the nature of the rot - is it a 'brown rot' or a 'white rot'? Brown and white rots: Brown rots: Brown rots cause the wood to crack in a cuboidal manner; the wood also goes slightly darker in color. The 'cubes' may vary in size depending on the wood and conditions, but they are generally very visible and distinct especially as the wood dries. There are many 'brown rots', dry rot (Serpula lacrymans) being just one. Thus, if the rot is identified as one of the brown rots then it could be dry rot. White rots: Wood attacked by a white rot looks completely different to attack by a brown rot: The wood takes on a 'fibrous appearance and tends to go slightly lighter in color ( this may not be too noticeable). There is no cuboidal cracking as in the brown rots.

Tend to be more common in hardwoods If the damage is shown to be from one of the white rots then it is certain that the rot isn't dry rot (dry rot is a brown rot) Once you have established the basic type of rot - brown or white, then one can start looking at the features which will help you identify the precise rot causing the damage. You should also note that the term 'dry rot' refers to one particular organism only - Serpula lacrymans. All other rots are colelctively refered to as 'wet rots'. Please note that the following is just a guide and will not list all the possible wood rotting fungi which may be causing a problem. Basic structures on which recognition can be made:- The wood: The basic nature of the rot will cause the wood to break into cuboidal cracks (brown rots) or take on a very coarse fibrous appearance (white rots). However, it is also useful to know whether the wood is a hardwood or a softwood as some rots will only attack one or the other. The fruiting body: This is the 'mushroom' stage of the rot, ie, the reproductive stage.

If there is a fruiting body then, in general terms, it is much easier to identify the rot. Unfortunately one can find atypical forms of fruiting bodies. The mycelium: This is the 'body' of the growth and consists of masses of very fine filaments (hyphae). It is the mycelium which secretes the enzymes, special chemicals, which break down the wood components into much simpler materials, ie, simple sugars, which the fungus can use for nutrition, growth and survival. Strands: Some rots form 'strands' which are effectively a group of thick walled hyphae. There function is to transmit 'food' (breakdown products of wood) to the growing mass. Brown rots: Dry rot (Serpula lacrymans): Almost certainly the most 'feared' of the rots, and sometimes called the 'cancer of a house'. However, like ALL wood rotting fungi, it requires water to become initiated, to grow and survive. Dry rot is restricted to damp humid conditions; this makes it sometimes very difficult to find. Dry rot has the ability to grow over and through materials from which it gains no nutritional value, eg, soil, plaster, mortar.

BUT IT CAN ONLY DO THIS EFFECTIVELY IF SUCH MATERIALS ARE DAMP - IT WILL NOT GROW OVER AND THROUGH GENUINELY DRY MATERIALS!!. Thus, if there is dry rot in, say, flooring timbers it will not grow up through the masonry of the walls and effectively rot the rest of the house if such walls are dry. So what are the points one should look for? Serpula lacrymans spores The wood: Typical cuboidal cracking of a brown rot, sometimes the cubes being quite large. Prefers softwoods to hardwoods. The fruiting body: Typically a 'pan-cake' or bracket, quite fleshy with an outer white margin. The surface within the margin is a rust red color and consists of large pores. The fruiting body or indeed an area where fruiting bodies exist may be covered with a fine rust red colored 'dust' - these are the millions of spores ejected by the fruiting body. However, nothing will happen to these spores unless they are on a suitable and damp substrate, ie, damp wood.

If they land on dry wood then nothing whatsoever will happen provided the wood stays dry - remember dry rot requires water to initiate, grow and survive; dry wood doesn't rot!!. The mycelium: This is effectively the main body of the fungus and is often present in sufficient quantity to be visible. It may take on several forms depending on the conditions. Points to look for: 1. White fluffy cotton wool-like growth; usually found under humid conditions. Under some relatively rare very damp conditions droplets of water may be seen on the growth. 2. A 'skin-like' growth, usually fairly flat. May be a 'mushroom' color of a silvery-grey skin. Both can sometimes be tinged with patches of lilac or yellow coloration. These skins peel like a mushroom head. 3. Distinct thick tubular-like growth (strands) which may be up to 3mm diameter, but often smaller. Usually gray in color and embedded in the mycelium in which they develop; can sometimes be found on their own. When dried they become brittle and distinctly crack when bent, ie, they are brittle when dry.

Strands are capable of growing over and through DAMP materials, and it is these structures that allow the rot effectively to spread from timber to timber via the damp substrate: it is the strands that make dry rot so potentially dangerous. 1. The Cellar fungus (Coniophora puteana): The most common rot found in properties (Coniophora marmorata looks the same). Frequently associated with timbers in contact with damp masonry, the masonry just being damp (capillary bound water) rather than a distinct source of water ingress as for dry rot. Hence it is very common in skirtings agaisnt a wall affected by rising damp, built-in floor joist ends and also in timbers subject to long term severe condensation. So points to look for: The wood: Typical cuboidal cracking as for all brown rots; the 'cubes', however, are usually found to be smaller than for dry rot. On interesting feature of the fungus is that the wood is often decayed internally, a very thin surface veneer of sound timber being left.

Where it occurs in timbers subject, for example, to subfloor condensation the surface may appear slighly concave due to the internal rot causing the wood to shrink. The fruiting body: Reported not to be common so it may not be found. Usually a thin tough flat olive brown plate with small lumps on the surface. May have a pinkish-white margin. The mycelium: Not always present so there may be occassions where this rot may be difficult to distinguish from dry rot. The mycelium usually develops under more humid conditions so, for example, it might be found on the back of a skirting fixed to a damp wall. In its early stages it appears white but usually when found it is olive brown to black, sometimes quite thin and other times in distinct sheets. This fungus also produces strands which can also move over VERY DAMP inert materials, but do not pose the problem like dry rot. Unlike the strands of dry rot, cellar fungus strands are usually fine with no real strength; usually brown or black in color.

Often seen emanating from infected wood The Mine fungus (Antrodia vaillantii - formerly Fibroporia vaillantii) - a wet rot Far less common than the Cellar fungus and Dry rot, which probably consititute over 90% of rots found in the domestic environment. Attacks softwoods. A wet rot causing typical cuboidal cracking, the cracks breaking the surface; it is often misidentified as dry rot. The wood: Typical brown rot damage - cuboidal cracking, the cracks readily being viewed on the surface like dry rot. If there is no mycelium then it will be very difficult to recognise The fruiting body: Usually easy to identify, it is somewhat fleshy, up to around 12mm in thickness, and is pure white but sometimes seen with a tinge of orange color. However, the most striking feature is that the surface has a 'honeycombed' appearance when viewed from above; the opening to the pores are angular and small (2 - 4 to the mm). The mycelium: Where present it takes on a 'fern-like' appearance, rather like frost fanning out on a window. Again, like the fruiting body, it is pure white.

The fungus also produces strands: these are what usually lead to a misidentification, the fungus often being confused with dry rot. However, there are 2 big differences, (1) Antrodia strands are flexible when dry (c/f. dry rot), and (2) they are usually pure white. Phellinus contiguus - a wet rot: Phellinus is probably one of the most common white rots found in buildings. Indeed, it caused significant problems in softwood window and door joinery in houses built in the 1950's and '60's. Attacks both softwood and hardwoods The wood: Typical white rot damage, the wood breaking down into very coarse fibres, slightly bleached in color. Frequently tufts of the tawny colored mycelium can be seen in the cracks of the decaying wood (see below) The fruiting body: Phellinus forms a dark brown, hard 'woody' fruiting body, often quite thin, and remains on the wood. It appears somewhat like looking at the end of rolled up very fine corrugated paper when viewed from the top, ie, it has very fine irregular shaped pores.

If a section of the fruiting body is viewed under a microscope you might see dark 'hairs' (setae) protruding into the pores. The mycelium: May form tawny colored sheets which remain on the wood. However, it is more likely that one will see tawny 'tufts' of the mycelium between the cracks in the fibrousy rotted wood (see arrow). There are no strands.

Question: What is the name for a condition of decay in timber caused by attacks of fungi?
Answer: Dry rot