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 rUNGUS AND TERMITE DAMAGE IN DDIEDINGS 
 
 June 1931 
 
 rtiAtft ^\ 
 
 
 
 
 No. E1C90 
 
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 mm cf aodh 
 
 UNITED STATES DEPARTMENT OF AGRICULTURE 
 FOREST SERVICE 
 FOREST PRODUCTS LABORATORY 
 Madison, Wisconsin 
 
 In Cooperation with the University of Wisconsin 
 
(Reprint from. The Octagon, a Journal of the A. I. A., June 1931) 
 
 FUNGUS AND TERMITE DAMAGE IN BUILDINGS 
 
 By CARL HARTLEY and WILLIS tf. WAGENER 
 of the U. S. Bureau of Plant Industry 
 
 Editor's ITote: — The paper on "Termite and Fungus Damage in Buildings," by 
 Mellen C. Greeley, A.I. A., published in the March number of The Octagon, was 
 submitted to the authors of the paper which follows. In turn, both articles 
 were submitted to Mr. George M. Hunt, in charge of the Section of Wood Pres- 
 ervation, of the Forest Products Laboratory, Department of Agriculture, 
 Madison, Wis. His observations will be found at the conclusion of this 
 section. 
 
 The Institute takes this opportunity to thank Mellen C. Greeley, A.I.A. , 
 Dr. Hartley, Mr. Wagener, and Mr. Hunt for their valuable contributions to 
 a subject which, apparently, is of great interest to the architectural pro- 
 fession in a large number of states. Requests for more than a thousand re- 
 prints of Mr. Greeley's article have been filled. In anticipation of like 
 interest in the papers appearing in this number, reprints have been ordered 
 which will be available on request, and without charge except in large quan- 
 tities. 
 
 The writers have been given the opporUxnity to supplement the excel- 
 lent article on the above subject by Mr. Greeley in the March number of The 
 Octagon. 
 
 The rots, due to fungi, are emphasized in the present paper, not be- 
 cause of any failure to appreciate the importance of termites, but because 
 the writers are engaged in the study of fungi. Only a termite expert would 
 presume to add materially to Mr. Greeley's treatment of the termite phase of 
 the subject. 
 
 The technical facts so far as they are known are better presented 
 in bulletins already existing than they can be here. Well-illustrated pub- 
 lications are available on building rots in general,— on decay in mill 
 
 ^Humphrey, C. J. Timber Storage Conditions in the Eastern and Southern 
 States with Reference to Decay Problems. U. S. Dep't. Agr. Bui. 510. 
 May 17, 1917. 
 Humphrey, C. J. and L. E, Miles. Dry-rot in Buildings and Stored Materials 
 and How to Combat It. The Alabama Polytechnic Institute, Extension 
 Service, Cir. 78. Feb. 1925. 
 Hubert, E. E. The Cause and Control of Decay in Buildings. Univ. of Idaho 
 Bui, 24, "Jo. 2. Jan. 1929. 
 
 Mimeo. .To. R1090 -1- 
 
construction,— and on termite injury.^* The termite shields mentioned by Mr. 
 Greeley are described in detail in publications by Dr. Snyder of the U, S. 
 Bureau of Entomology. 3 - The best contribution that can be made here will be 
 to pre rent a general picture of the situation with respect to the organic 
 enemies of wood in construction, and discuss briefly some of the fundamental 
 factors affecting the fungi. 
 
 The ordinary mould fungi, although some of them grow luxuriantly in 
 sapwood and discolor it, so far as we now know have little or no effect on 
 the cell walls of wood and need not be considered here. On the other hand, 
 the wood destroying fungi, of which there are some dozens of fairly common 
 species, grow not only in sapwood but also to a considerable extent in heart- 
 wood of all but the most extremely durable species. They corrode the cell 
 walls or dissolve some of their essential constituents thus affecting the 
 mechanical properties of the wood. Wood that has been recently infected may 
 still be normal in all the easily determined characteristics, such as color 
 and density, and may be scarcely reduced in resistance to compression paral- 
 lel to the grain, but in certain other qualities may be measurably injured. 
 Infected wood may become brash and lose most of its resistance to impact 
 bending before it shows any signs of infection that superficial examination 
 would detect. The decay fungi in their early development rarely produce 
 fruiting bodies and cause no such mechanical signs of their presence as do 
 the wood- tunneling insects, with the result that incipient decay often goes 
 unrecognized. 
 
 As Mr. Greeley has indicated, the moisture content of wood is the most 
 important of the easily controlled factors that govern decay liability. Ho 
 decay is believed to take place in wood that does not have at least 20 percent 
 of moisture (oven dry weight basis). Many fungi can persist in air-dry wood 
 in a dormant state for _onths or years ready to start growth when supplied 
 with moisture, but it is probable that for most of the fungi from 21 to 25 
 percent is a uinimum for actual growth. It is only at high humidities or low 
 temperatures that wood in equilibrium with air will contain more than 20 per- 
 cent of moisture. If wood is thoroughly air-seasoned to start with and pro- 
 tected from water or excessive humidity, it is permanently safe from attack 
 by most fungi. The only exception to this occurs in the so-called dry rots. 
 This term is technically limited to the work of two notorious fungi, Merulius 
 lachrymans and Poria incrassata , which can bring water with them from some 
 source of moisture. This water-conducting ability makes them the most dan- 
 gerous of the structural fungi. Strictly speaking there is no such thing as 
 a dry rot in wood. On the contrary when the causal fungi are at the height 
 of their activity, such decays are very moist and it is only after fungus 
 action has nearly ceased and the contained moisture has had a chance to evapo- 
 rate that the decay assumes the dry, rectangularly checked form from which its 
 common name is derived. 
 
 — Hoxie, F. J. (Inspection Department, Associated Factory Mutual Eire 
 Insurance Companies.) Decay of Wood in Industrial Buildings, 1930. 
 
 •^Snyder, T. E. Preventing Damage by Termites or White Ants. U. S. Dept. 
 Agr. Farm. 3ul. 1472. 1926. 
 
 Snyder, T. E, Termites in Buildings, U. S. Dept. Agr, Leaflet 31, 1929. 
 Light, S. F. , Merle Bandall, and F. G. White, Termites and Termite Damage. 
 Berkeley, Calif., Agr. Exp. Stat. Circ. 318. 1930. 
 
 Mimeo. 2To. KL090 -2- 
 
Whereas most fungi can attack only wood that has retained its moisture 
 after it has "been put into the building green or has absorbed water from 
 leaks, stagnant damp air, moist soil, or cold surfaces on which it has con- 
 densed, the water-conducting fungi, starting at a source of moisture, can ex- 
 tend rapidly into comparatively dry wood. Dry rot has been known to reach 
 the third floor of a building in regular occupancy. The moisture that ap- 
 pears in wood infected by these two fungi may be in part absorbed from the 
 air as Mr. Greeley suggests, but is probably supplied in the main by trans- 
 portation through the strands of fungus threads extending from the water sup- 
 ply at the point of origin or from wood in which they are already working 
 actively. Water is formed in the decay process through the oxidation of the 
 wood substance by the fungus, and there is evidence to indicate that once 
 these fungi are actively established in a closed situation where the evapora- 
 tion loss will not be great, conduction of water from the original source may 
 be cut off and the fungi will still be capable of progressing for a time by 
 means of the metabolic water resulting from the breaking down of the v:ood. 
 This is one reason for the recommendation that in treating an active case of 
 dry rot in a building all wood to well beyond the limits of the decay should 
 be removed. However, a source of moisture must be available before these 
 fungi can get an active start in the first place. Because of their water- 
 conducting ability, it is necessary for the safety of the entire wooden 
 structure that no part of it be in direct contact with the soil or with moist 
 concrete -unless it is heartwood of a highly durable timber species or has had 
 pressure treatment with an efficient wood preservative. 
 
 The increase in the menace from fungi and termites mentioned by Mr. 
 Greeley is traceable to a number of different causes, some of them connected 
 with changes which have taken place in the character, distribution, and use 
 of our lumber supply. For example, with the passing of the virgin forests 
 over large parts of the country an increasing proportion of the lumber used 
 is sapwood. It is well known that even in timber species with extremely 
 durable heartwood the sapwood is not strongly resistant to either termites 
 or decay and it is therefore not surprising that the greater use of sapwood 
 should be accompanied by some increase in damage. 
 
 Changes in architectural styles have tended to provide another source 
 of increased hazard, particularly from decay. Whatever the architectural or 
 other shortcomings of the nineteenth century American wooden house, in most 
 parts of the country it was built well off the ground and was provided with 
 plenty of underneath ventilation. The trend in recent years toward Old World 
 exterior design based on types built directly on the ground with stone, tile, 
 or earthen floors has resulted in a general lowering of first floor levels so 
 as to bring them as close to grade as possible. With this has come the sub- 
 stitution, for the piers that formerly served as foundations in the Southern 
 States, of solid foundation walls which interfere with ventilation under the 
 lower floor. 
 
 Coupled with the later trends in house design lias been the extensive 
 use of stucco and waterproofed building papers in sections of the country 
 where wooden exteriors were formerly the rule. If building paper was used at 
 all in the older construction it was likely to be of the familiar gray felt, 
 nonwaterproof type, employed solely to reduce air leakage. Perhaps because 
 the newer type of construction allows less ventilation of the wooden members 
 
 Miraeo. Ho. 21090 -3- 
 
of the wall, there seems to have been more trouble in stucco houses than 
 where siding is used. Moreover the use of large or conspicuous ventilators 
 at the ground floor level is not in harmony with good stucco design from the 
 standpoint of appearance and in consequence the tendency, is to cut such ven- 
 tilators to a minimum or to place them where they will be inconspicuous with 
 their ventilating efficiency left as a secondary consideration. The effec- 
 tiveness of such ventilators as are present is often reduced by stucco dash 
 splattered over the screens, or by the close planting of shrubbery in front 
 of them. 
 
 liven within the house chances for evaporation of excess moisture are 
 being reduced through the wide adoption of cemented linoleums and similar 
 waterproof floor coverings. Cases are known in which buildings have been 
 used for years without any trouble from decay as long as the floors were not 
 covered, but in which rot developed rapidly as soon as cemented linoleums 
 were laid. This is an argument not against linoleum, but for attention to 
 subsurface moisture conditions when linoleum is to be used. 
 
 The reduction in opportunity for evaporation from walls and floors has 
 assumed an added significance in those sections of the country where the use 
 of unseasoned or partly seasoned lumber for framing, subfloors, and sheathing 
 has become common practice. Under this development, green lumber can be laid 
 down on the job cheaper than the seasoned product. There is also a tendency 
 to leave dry lumber exposed to rain after delivery, or to use subflooring 
 for concrete forms before it goes into the building, practices which proba- 
 bly result in considerable moisture pick-up in some cases. In using wood 
 that it not air-dry, the builder is gambling that sufficient drying vail 
 occur during handling and in the course of erection to render it safe from 
 decay. The fact that he does not always win adds just another source for the 
 increase in decay liability. 
 
 Hot the least of the losses from the organic enemies of wood are 
 traceable to the increase in speculative building. Too often the builder is 
 more interested in cost cutting than in the permanence of his structures and 
 oversteps sound building practice in the attempt to get a few more dollars of 
 profit. It is the hidden details which offer the best chance for slighting 
 and short cuts and it is these same hidden spots which are most likely to be 
 the site of fungus attack. 
 
 Looking at the matter from another angle we can say that the diffi- 
 culties are chargeable in some degree to a lack of knowledge on the part of 
 architects, builders, and the general public of the chance of injury to wood 
 and to other building materials of organio composition from the activity of 
 fungi and insects. It might improve the situation if the courses in biology 
 at colleges that feature architecture or engineering were to include wood- 
 tunneling insects and wood-rotting fungi among the organisms U6ed as illus- 
 trative material. No animals could be more interesting than the termites 
 with their social organization and complex symbiotic relationships. These 
 practically important organisms might prove quite as valuable for general 
 educative purposes as lichens, diatoms, or starfish. In default of such as- 
 sistance from biology, the architect's professional training might conceiva- 
 bly include a little special instruction as to how wood is decayed and how 
 termites and powder-post beetles live and work. 
 
 Mimeo. No. R1090 ~4~ 
 
A good builder is rarely guilty of putting in direct contact with soil 
 untreated wood of any "but the most extremely durable species, but many are 
 content to leave it separated from soil only by a layer of stucco, or actu- 
 ally to imbed floor stringers in concrete that is in contact with soil. 
 
 An altogether inexcusable fault is the leaving of piles of wood trash 
 under the building in contact with the joists, and wooden concrete forms 
 still in place where they can serve as a convenient route through which fungi 
 and termites can get up from the soil into the building. No wood trash 
 should be left under the building. 
 
 Incipient decay present in the lumber when it is delivered on the job 
 and originating in the logs or from improper seasoning or yard storage condi- 
 tions of the lumber has undoubtedly played a part in subsequent fungus de- 
 velopment in erected buildings. Although there has been a decided betterment 
 in lumber yard storage practice during recent years, some room for improvement 
 still remains. Studies are now under way in cooperation with the American 
 Pitch Pine Export Company on the surface treatment of logs and freshly sawed 
 lumber to prevent sap stain, and as an important byproduct of the studies it 
 is expected that the treatment will also reduce the chances for the estab- 
 lishment of incipient decay infections during the period of seasoning and 
 storage. Not all traces of early stages of decay which may be found in 
 lumber are necessarily dangerous. The true "sound red heart" of pine and 
 other softwoods is an example. This is due to the incipient attack of a 
 specific fungus, Trametes pini , that works in the living tree, b\;t does not 
 ordinarily continue to develop after the lumber has been properly seasoned. 
 Such lumber, while reduced somewhat in strength, is perfectly suitable for 
 certain purposes. The ordinary sap stain, due to fungi very different from 
 those that cause decay, is believed to have little if any weakening effect. 
 The failure to differentiate between different kinds of fungus defects has 
 sometimes caused the needless rejection of lumber; but lumber suspected of 
 fungus infection should be accepted only after inspection by someone familiar 
 with the different types. 
 
 Treated lumber suitable for small house construction is not yet ob- 
 tainable in all parts of the country. The National Committee on Wood Utili- 
 zation, The American Wood-Preservers' Association, and cooperating agencies 
 are making an effort to improve this situation by prevailing on distributors 
 to stock lumber treated with standard preservatives, and have already met 
 with some success in Ohio. 
 
 On most of these points the remedy is obvious and the chief need is 
 a campaign of education. There are, however, a number of respects in which 
 present knowledge is not an adequate basis for setting up positive recom- 
 mendations. Decay has been little studied from the standpoint of the small 
 house or building and there is a danger that we may go too far in setting up 
 safeguards and thus jeopardize their chances for being put into general 
 practice. Prevention practices must be both inexpensive and simple. On a 
 number of points the basic facts are not yet sufficiently determined to per- 
 mit recommendations that meet this requirement. 
 
 As examples of subjects on which further information is needed the 
 following may be mentioned: 
 
 Mimeo. No. RIO 90 -5- 
 
(l) '/fhat indications of fungus infection are proper causes for re- 
 jection of lumber? 
 
 (3) Minimum requirements for safe ventilation of basements and under 
 houses in different types of situations. A ventilation ratio which proves to 
 be entirely satisfactory for one region or set of conditions may be very in- 
 adequate in others and no authoritative data exist on which to set down rules. 
 
 (3) The effect of chemical disinfection of underlying soil or concrete 
 on the incidence of decay in wood above. It is entirely probable that 
 trouble v/ith floors laid on concrete can be easily and cheaply prevented by a 
 proper antiseptic in the concrete. 
 
 (4) She relations between the soil-nesting termites and decay fungi. 
 There sometimes appears to be a connection between the activities of the two. 
 
 (5) Better information on the origin of decay infections. There is 
 still some question as to how the majority of infections are brought about, 
 whether oy wind-borne spores of the fungus, by vegetative spread in wood or 
 soil, by direct contact of sound v/ith infected wood, or by other means. 
 
 (6) Determination of representative moisture contents actually present 
 in the wood of different parts of a building and closer definition of the 
 maximum safe moisture content of wood from the decay standpoint. Preliminary 
 studies of this sort are nov; under way by the Forest Service and Bureau of 
 Plant Industry. 
 
 (7) There is still some question as to what preservatives can be used 
 safely end effectively in dwellings, and an effective technic is needed for 
 orotecting ends of treated timbers that are cut on the job so that untreated 
 cores are exposed. 
 
 (8) Further experimental study on the control of decay infections by 
 heat or by the in-place application of toxic substances. Dry heat has been 
 used successfully against Merulius lachrymans infections, while steam has 
 been employed with striking results in killing infections in the roofs of oil 
 storage tanks. 
 
 The elimination of infections that have already gained a foothold in 
 buildings is also in need of attention. There are too many cases on record 
 of householders and even professional builders who have made repeated at- 
 tempts to exterminate either termites or the dry-rot fungi, only to have the 
 attack promptly renewed and extended and the whole process in need of repe- 
 tition. As an extreme example, a hardwood floor replaced after attack '^j a 
 dry-rot fungus in a new brick school building in Texas was ruined in six 
 months. The residence mentioned in Mr. Greeley's first paragraph is a par- 
 ticularly interesting case. There is need of field follow-up studies to 
 determine the cause of these failures. Our -ore sent knowledge leads us to 
 believe that any infection can be definitely stopued at the first attempt 
 if the right methods are followed. The principles are known, but the de- 
 tails evidently require further attention. 
 
 Mimeo. "0. £1090 -6- 
 
* r c know that the cases of trouble that are reported are usually from 
 buildings where certain precautions have been neglected; but v;e know also 
 that there are great numbers of houses in which some of those same precau- 
 tions have been ignored, and which nevertheless have given decades of cred- 
 itable service without any termite or fungus injur;/. The cases of acute 
 injury from dry-rot fungi are particularly difficult to trace to specific 
 malpractices, since the hazard from these fungi is somewhat like fire hazard; 
 there are many houses whose construction would seem to lay them open to such 
 attack, but the damage is concentrated in a few. What is needed is a survey, 
 in which both termite and fungus investigators take part, in consultation 
 with architects, engineers, and builders, and supported by supplementary lab- 
 oratory studies. These should be extensive enough to enable us to say for 
 each of the several important regions of the country what malpractices are 
 really dangerous enough to deserve stress. For a successful campaign of 
 education, or for improvement of municipal building codes, we must know what 
 precautions are unnecessary and can be omitted, as well as what to emphasize. 
 Building rots are not now being studied anywhere in the United States. The 
 termite problem is being investigated comprehensively only as it affects 
 California, on funds from California sources; termite study on a comparable 
 scale is badly needed in other parts of the country. 
 
 The writers wish to join Mr. Greeley in avoiding the appearance of 
 pessimism. Wood is the natural building material for many purposes, and par- 
 ticularly in small dwellings and farm structures, generally it is expected to 
 remain so. In millions of buildings in the United States it has given thor- 
 oughly good service for long periods of time. The cases of real trouble, 
 while numerous enough in the aggregate to require attention, are relatively 
 infrequent when the whole number of structures is considered. There is every 
 evidence that wooden construction can be made safe without any undue expense 
 or sacrifice of aesthetic values. Investigation in the direction of simpli- 
 fying safeguards, and followed by an educational campaign, should reduce the 
 insect and fungus hazard to negligible proportions. 
 
 Comments on Preceding Papers 
 
 By George M. Hunt 
 Forest Products Laboratory 
 
 After having read Mr. Greeley's article which you enclosed and the 
 manuscript of the article by Dr. Hartley and Mr. Wagener, it seems to me that 
 there is very little I could add to the discussion of decay and termite dam- 
 age and their prevention that would be of interest to your readers, lit*. 
 Greeley points out the necessity for sanitation, care in selection and con- 
 struction, and the provision of safeguards that are necessary for the protec- 
 tion of buildings in termite infested territory. If his recommendations, 
 which are substantially those of the U. S. Bureau of Entomology, are followed 
 with care, I think there is little likelihood of serious damage by termites. 
 
 Mimeo. No. H1090 -7- 
 
Similarly. Dr. Hartley and Mr. Wagener show how decay may be avoided. Fortu- 
 nately the methods that are effective against one are for the most part ef- 
 fective against the other. 
 
 Suitable preservative treatment will undoubtedly protect wood in 
 buildings from termite destruction and decay, but throughout most of the 
 United States it is at the present time not very practicable for a man to 
 secure properly treated wood in the sizes and small quantities needed for 
 residence construction. It is a simple matter for large consumers like rail- 
 roads, other public utilities, and the like that use large quantities to 
 secure treated timber especially suited to their needs, either from their 
 own treating plants or from commercial treating plants. It is not easy, how- 
 ever, for the small consumer to secure the kind and quantity of treated ma- 
 terial he needs for there is as yet, except in very few cases, no provision 
 for the retail distribution of well treated lumber. In a few cities in Ohio 
 the National Committee on Wood Utilization with the cooperation of wood pre- 
 serving companies and lumber dealers has made treated lumber available in 
 retail lumber yards. I believe treated lumber can also be obtained at a few 
 retail yards in St. Louis, in southern California, and Florida, and perhaps 
 a few other places, but thus far this opportunity is very limited. Until 
 adequately treated lumber becomes more generally available to the house- 
 builder he cannot make much use of it. 
 
 Lumber can, of course, be dipped or brushed with preservative by the 
 contractor as the building is constructed, but treatments of this kind are 
 very superficial in character and cannot be counted upon for much protection 
 even when conscientiously made. In some cases, no doubt, the treatments 
 would not even be conscientiously made. For these reasons, therefore, it 
 seems to me that the principal hope for both termite and decay prevention in 
 small buildings at the present time lies in observing the precautions discus- 
 sed by Dr. Hartley and Mr. Greeley rather than in relying upon preservative 
 treatment. 
 
 
 
 
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