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Proposed method for out-of-ground contact trials of exterior joinery protection systems
1981 - IRG/WP 2157
Methods for testing the efficacy of preservative treatments for exterior joinery are described using the format of a European Standard. Commercially used treatments applied to jointed test units (L-joints) which are then protected by conventional finishes are exposed to normal outdoor hazards out of ground contact. Assessment is made a) by determining eventual failure through decay and b) by destructive examination of replicate treated and untreated units, after increasing time intervals, rating comparative performance in terms of wood permeability increase and the progress of microbial colonisation.
J K Carey, D F Purslow, J G Savory


Exterior wood stains
1980 - IRG/WP 3135
Experience has shown that conventional paints cannot now be relied upon to provide a complete seal against water entry, that in practice water can often circumvent the film and that the paint, far from serving to keep water out will seal it in. Moreover present-day paints are often subject to localised and premature failure out of doors and consequently entail high maintenance costs. Problems of wood decay and premature paint failure reached a high level during the 1960s, and led to the acceptance of the need for the preservative treatment of softwood joinery and cladding. The question remains however, whether, in the light of changes in the quality of timber and how it is used, the traditional approach of attempting to seal the outer surface of the wood is still valid, or should be abandoned in favour of using different types of finish which are more permeable to moisture and prevent it accumulating in the timber. One of the reasons for the remarkable success of semi-transparent exterior wood stains is that they met the demand for finishes of increased water vapour permeability for timber which was susceptible to decay. They also possessed two other important attractions: they provided natural finishes for exterior timber which were without the technical problems of clear varnish; and their mode of breakdown by erosion reduced the preparation work in maintenance and hence the overall maintenance costs. These are valid commendations for stains and remain important factors encouraging their use. Stains offer the architect additional design freedom and, used effectively, can make a pleasing contribution to the appearance of modern buildings. They do reduce average moisture levels in the timber and are simple to maintain, though these advantages may be offset to some extent if more frequent maintenance is necessary and if the higher permeability creates problems from dimensional movement.
E R Miller


Impact of wood species on the performance of exterior wood coatings
2010 - IRG/WP 10-40519
To prolong the service life of a wooden construction the protective function of a coating is of utmost importance. The chemical composition as well as the wood-coating interface affects the performance of this protective layer and obviously wood species have an impact too. This paper discusses the influence of wood species on the overall coating performance. Therefore, a range of opaque waterborne acrylic coatings applied on industrially finished window frames made of frequently used commercial hardwood and softwood species were tested. Both, artificial and natural weathering, were considered for the durability assessment. Complementary studies on moisture dynamics and fungal growth were included as well. Coatings applied on dense tropical hardwood with large vessels perform fairly well in regard to water related failure, but erosion or weathering phenomena occur early. The opposite is true when examining small or medium porous hardwoods. Coatings applied on softwood substrates performed the worst. Yet, in contrast to hardwood, the performance of softwood based systems under laboratory test conditions is less correlated with outdoor performance.
I De Windt, J Van den Bulcke, J Van Acker


Finishes for outdoor timbers
1975 - IRG/WP 378
Anonymous


Wood preservatives: Field tests out of ground contact. Brief survey of principles and methodology
1976 - IRG/WP 269
This paper contains the following spots: 1.: The general need for field tests. 2.: Interests and limits of field tests in ground contact. 3.: Various methods in use for out-of-ground contact field tests. 4.: Fungal cellar tests are they an alternative to above-ground decay exposure tests? 5.: Conclusions.
M Fougerousse


Effect of protective additives on leachability and efficacy of borate treated wood
2002 - IRG/WP 02-30290
Borate preservatives have been used extensively in many countries as an effective means for protecting wood against fungal and insect attack especially in interior environments. Under exterior conditions, borate compounds have a main disadvantage as they can be leached from treated wood as a result of their water solubility. In this study, we compared the potential of different additives for reducing the leachability of boron preservatives from treated wood. Scots pine sapwood (Pinus sylvestris) and poplar (Populus trichocarpa x deltoides) test samples were vacuum treated with 1 % BAE (Boric Acid Equivalent) disodium octaborate tetrahydrate (DOT) solutions containing various additives e.g. glycerol/glyoxal, polyvinylpyrrolidone (PVPY), a commercial resin compound and a commercial water repellent. The European Standard EN 84 was used as a leaching test for both coated and uncoated specimens. The results of chemical analysis of leachates taken at different periods showed that the use of protective additives reduces the boron leachability. The glycerol/glyoxal additive applied to treated pine sapwood showed the best performance. The percent of boron retained in uncoated pine sapwood was 26% while coated samples still retained 45% after 14 days of intense leaching. Similar tests on poplar revealed 19% and 34% for uncoated and coated samples, respectively.This represents a gain of 20 to 25% compared to pure DOT treated specimens of both wood species. Preliminary biological tests were carried out on malt agar using a miniblock technique for uncoated pine sapwood and beech, with Poria placenta and Coriolus versicolor, respectively. After six weeks of exposure to fungal attack all boron protective systems tested proved their effectiveness, as none of the test samples exhibited a mass loss exceeding 4%. The reference 1% BAE without protective additives showed an average mass loss of 15%. Finally, test data are reported of standard EN 113 testing in view of a further evaluation of the biological efficacy of combined DOT-additive treatments.
A Mohareb, J Van Acker, M Stevens


Local preservation with difluoride pills: Life-time of preservative
1998 - IRG/WP 98-40127
A brief history of the situation in the Netherlands with respect to the preservation of joinery is given. Already in the eighties in the Netherlands many spruce window frames were treated with difluoride pills. One of the possible disadvantages of this kind of diffusing preservatives is the high leaching rate found in laboratory situations. The leaching rate in practice is influenced by many factors of which the condition of the paint systems and the condition of the glue in the joint are the most important. In this research the difluoride content in wood was analysed in samples which were taken from several buildings. An estimation of the remaining difluoride content leached is given. Related to these figures the remaining life of the protecting agent can be calculated. The results show that even in situations with open joints of paint damage the remaining amount of difluoride is still very high after 10 years. This suggests that in practice the leaching of difluorides is of minor importance.
W J Homan, C Blom, B W Holleboom


The long-term performance of boron treated joinery in service - A case study
2000 - IRG/WP 00-20208
Joinery treated with borates 23 years ago and in service in residential flats was surveyed and analysed for boron content. The levels of boron still present were sufficient to prevent decay. None of the windows surveyed showed any decay despite the fact that moisture and sapwood contents were conducive to decay.
D J Dickinson, R J Murphy


Detoxification of preservatives: Tri-n-butyltin oxide as a biocide
1982 - IRG/WP 1156
T E Dudley-Brendell, D J Dickinson


Decay in external joinery in the United Kingdom
1978 - IRG/WP 3116
no abstract available
J G Savory, J K Carey


An approach to testing the preventive effectiveness of preservative treatments for wooden joinery
1981 - IRG/WP 2156
The ecological sequence established in field trial samples exposed out of ground contact has shown the need for outdoor exposure in testing potential joinery preservative pretreatments. A system of exposure of L-joint units is proposed. Data obtained by examining samples destructively show promise as the basis for predicting service life after relatively short exposure periods (within 2 years).
J K Carey, A F Bravery, J G Savory


Gloeophyllum trabeum and Gloeophyllum abietinum, the most frequent brown rot fungi in fir wood joinery
1999 - IRG/WP 99-10319
In Croatia the primary raw material for joinery production is silver fir wood (Abies alba Mill). L-joints made of home-grown fir sapwood and prepared according to EN 330: 1993 were used to establish the infection and colonisation of micro-organisms, particularly wood decay fungi, to compare the performance of untreated and 1% TnBTO treated L-joints. The L-joints were coated with two types of coat, and 36 months exposed in Zagreb. The first type of coat was alkyd paint and the second was a stain, in three different colours: white, brown, and black. The influence of the preservative, and the type of coat were most important factors which affected the rate of colonisation. The influence of coat colours was significant at the the beginning of exposure. The fastest and the strongest colonisation occurred in untreated L-joints coated with alkyd paint and the lowest colonisation occurred in treated L-joints coated with stain. It was due to the well known vaporous diffusivity of the stains and the low natural permeability of fir sapwood. The most frequently isolated fungi were Gloeophyllum trabeum (Pers.: Fr.) Murr. and Gloeophyllum abietinum (Bull.: Fr.) Karst.
R Despot, M Glavas


Exterior weathering trials on radiata pine roofing shingles
1985 - IRG/WP 3240
A series of test roofs clad with radiata pine (Pinus radiata D. Don) shingles that had been pressure-treated with various water-borne preservative formulations were installed at a Forest Research Institute test site in Rotorua in 1977. A further series of test roofs installed in 1978 included radiata pine shingles pressure-treated with a commercial light organic solvent preservative (LOSP). Evaluation of selected radiata pine shingle test roofs in early 1984 showed that, although preservative leaching had occurred from shingles treated with an alkyl ammonium compound (AAC), a copper-chrome-arsenic (CCA) preservative, and an LOSP, the shingles appeared sound when examined microscopically. Slight lichen growth was evident on some shingles. In contrast, untreated radiata pine shingles displayed marked fungal infection, early stages of decay, and plentiful mould and lichen growth. Western red cedar (Thuja plicata D. Don) shingles, which were used as a reference point from which to judge radiata pine shingles, showed lichen and mould growth after seven years' exposure. Checking and cupping of western red cedar shingles were attributable in part to the inclusion of some flat-sawn material.
D V Plackett, C M Chittenden, A F Preston


The rate of redistribution and loss of leachable preservatives under service conditions
1993 - IRG/WP 93-30026
This paper describes experiments carried out to determine patterns of preservative redistribution and any associated losses which occur when wood containing unfixed water-soluble wood preservatives is exposed to service conditions where leaching is possible. Scots pine sapwood treated with disodium octaborate was used as a model system. Results are recorded and discussed for trials representing painted joinery out of ground contact and unpainted stakes half buried in the ground. The results indicate that in the painted samples out of ground contact the water-soluble compound was redistributed longitudinally and away from the joint zone during the first months of exposure, although little redistribution occurred laterally. No difference in redistribution patterns could be associated with paint type. Ground contact stakes showed a loss in the water-soluble compound of about 40% in the first six months exposure. Most of this appeared to occur from the surface zones of the stake exposed to the weather, particularly from the extreme top. In addition, the compound appeared to migrate upwards from the below-ground portion of the stake to the above-ground portion. These results provide new information on the extent of movement of water-soluble preservatives in painted, jointed timber out of ground contact and in unpainted timber in ground contact. It is concluded that the long-term significance of the observed redistribution effects for painted joinery should be evaluated to confirm that there is no likelihood of shortcomings in performance in practice. For the ground contact situation, results confirm that rates of redistribution and loss are high enough to indicate inappropriateness of such materials for practical use without associated technologies to reduce mobilities.
R J Orsler, G E Holland


The use of bifluorides-diffusion in remedial treatments
1983 - IRG/WP 3256
A description is given about the experience to date of a 14 years' development to bring bifluorides-diffusion from laboratory evaluation to commercial service application. The described treatment is an adjunct to good design and not a replacement for it. The process is also used with an injection method for the remedial treatment of premature decayed external joinery.
H F M Nijman


The window joinery test hut
1975 - IRG/WP 257
D F Purslow


Protecting wooden structures
1980 - IRG/WP 392
Chromium-containing chemicals that effectively retard weathering of wood improve performance of subsequently applied finishes. Current work is focusing on the performance of wood-derived products (plywood, hardboard, fiberboard, particle board) after surface treatment with inorganic chemicals. The overall objective of the continuing research is to investigate new environmentally safe procedures to stabilize wood surfaces and to improve performance of applied finishes.
W C Feist


The use of zirconium as an inert fixative for borates in preservation
2001 - IRG/WP 01-30256
Stand-alone borates have been used in internal protected situations as wood preservatives for about 60 years. They have not been deemed acceptable for external situations because of their leaching characteristics. Work carried out to reduce the leachability of borates has been reviewed briefly here, and a specific fixation agent based on zirconium has been tested in standard leaching and decay tests. It was found that the performance of zirconium could be optimized for fixation at specific drying temperatures and at higher formulation pH. Using sufficient quantities of ammoniacal zirconium carbonate and potassium zirconium carbonate such formulations are then able to pass both Standard European and American Wood-Preservers' Association methods designed for testing exterior wood preservatives. Formulations based on borate with a zirconium additive are probably suitable for use in exterior above ground and possibly ground contact situations. As only initial indicative tests have been carried out so far, further testing with a range of wood destroying organisms and field tests should be carried out to evaluate this system further.
J D Lloyd, J L Fogel, A Vizel


TBTO absorption and penetration in pine joinery treated by various processes
1989 - IRG/WP 3523
Matched sections of several White pine (Pinus strobus) and Ponderosa pine (Pinus ponderosa) mouldings were treated with TBTO by Double vacuum, modified empty-cell, 15 second dip and several preheating treatments followed by a 15 s dip treatments. As expected the double vacuum and empty-cell (batch) treatments resulted in much greater retentions and penetrations than the dip treatments. The absorptions by the 15 s dip treatments could be improved significantly by preheating the wood to 60-90CĀ° by microwave, radio-frequency or infra-red techniques. Since this approach is amenable to a continuous treatment process, it is being evaluated for potential commercial application.
P A Cooper, Y T Ung


Preservative requirements for exterior particleboard as predicted from accelerated laboratory evaluations
1976 - IRG/WP 265
Arguments for and against preservative treatment of exterior particleboard were considered; it was concluded that preservative treatment is desirable. Laboratory decay tests were conducted to determine levels of sodium pentachlorophenoxide required to protect exterior particleboard from decay fungi. The decay resistance of treated board was compared with that of timber (both naturally durable and preservative-treated) currently used in situations for which exterior particleboard is designed. A retention of 0.35% sodium pentachlorophenoxide per oven-dry board weight was considered to offer adequate protection to the board.
M E Hedley


Remedial treatment of joinery. Comparison of distribution of organic solvent preservative and ammonium bifluoride
1978 - IRG/WP 3115
It is some years since it was recognised in the United Kingdom that there was a problem of premature decay in untreated external joinery. Consequently, recommendations for preservative treatment were made by the Building Research Establishment, Princes Risborough Laboratory. In addition, the National House-Building Council has also included the preservative treatment of external joinery in its requirements. Thus, a large proportion of external joinery manufactured in the U.K. is now preservative treated, mainly in double vacuum impregnation plants. There still remain, however, relatively new buildings where preservative treatment has not been specified and where fungal decay is a problem. Decay occurs most frequently in the lower horizontal members such as cills, and the lower rails of opening lights. The damage is often most severe at the joints, where entry of water is facilitated by exposure of end grain. In some circumstances such as in Local Authority buildings where some of the more exposed joinery has already decayed, it has been considered economic to treat the remaining sound or near-sound joinery in situ in order to prevent future attack and to arrest any slight decay that may already be present. This treatment is normally applied by injecting organic solvent preservative under pressure in the region of the joints and where considered necessary along the lower horizontal member. As an alternative method of treatment, we have investigated the possible use of ammonium bifluoride, since diffusion of gaseous hydrogen fluoride may be expected to penetrate more extensively into wet timber than organic solvent preservative. The work described below was carried out in order to assess the comparative penetration of fluoride and organic solvent preservative in redwood (Pinus sylvestris).
J M Taylor


Fluoride woodpill
1987 - IRG/WP 3431
Decay problems of spruce joinery in the Netherlands in the 1960's and 1970's led to the introduction of preservative treatment. Because of the known penetration difficulties with Spruce, the results of the treatments were not always successful. The fact that the decay was found only in the joints led to development of the philosophy of "local preservation" of the joints in remedial and preventative treatments, like preservative injections or use of rods and capsules containing preservatives. However the diffusion of the preservatives used in most of these systems is often poor in spruce. Because Spruce joinery dip-treated with bifluorides showed good penetration and protection, a pill consisting of a hydrophylic polymer and bifluorides was developed by TNO. Various laboratory tests carried out with this pill have confirmed good penetration of the bifluorides in the wood and activity against decay fungi.
J W P T Van der Drift, K J M Bonsen


Blue stain resistance of exterior wood coatings as a function of their typology
1998 - IRG/WP 98-20145
Paints and wood stains were evaluated on their blue stain resistance using both EN 152 method and the reverse method. The typology of these exterior coatings was varied including standard and high solid solvent-borne coatings as well as different types of waterborne coatings. For the water-borne acrylic, alkyd based and hybrid coatings both applied as opaque primer paints and as decorative wood stains a range of synthetic resins were used. Though some components like dryers or bactericides are present in a number of formulations examined, a clear tendency of dependence of blue stain resistance on the typology of the coating seems obvious when evaluating blue stain development in an early stage. Longer exposures to test fungi fade away the effect of resin and indicate the role of a chemical protection of the coating.
J Van Acker, M Stevens, C Brauwers, V Rijckaert, E Mol


Natural durability of European wood species for exterior use above ground
2003 - IRG/WP 03-10499
The main interest in using more timber for exterior constructions is to protect the environment, where wood is considered an environmentally friendly material. However, chemicals for wood protection are getting more and more restricted, consequently, the focus on the natural durability of wood is increased. Good, well-documented data on the durability of wood species in ground contact exist, which form the basis of the standard EN 350-2:1995. Yet, we have, however, no useful documentation for the natural durability of wood, when used outdoors above ground. The study is large-scale field trials, including more than 30 species, where the objective is to define and document the natural durability of European wood species when used outdoors above ground. The idea of the test set-up is to simulate different application situations of wood to recommend individual wood species for specific purposes ā€“ fit to purpose. Two basically different test set-ups are used: 1. Panels in close-to-practice applications: Horizontally oriented with and without covering. Vertically north turning and vertically south turning oriented with and without covering as well as 45 degrees south turning oriented without covering. 2. Lap-joints in standardised field exposures: The set-up is according to the CEN-standard ENV 12037: Wood Preservative ā€“ Field Test Method for determining the relative protective effectiveness of a wood preservative exposed out of ground contact ā€“ Horizontal lap-joint method. The paper presents the results of the appearance, the moisture fluctuation, mould growth and wood decay after 3 years field trial.
B Lindegaard, N Morsing


Xenon simulation of natural weathering of external joinery preserving - Finishing systems
1992 - IRG/WP 92-2412
Semitransparent wood stains ('lazures') for external joinery have developed by means of product combination towards complete wood finishing systems that are easy to applicate, have a good weathering resistance and low maintenance cost. The search for enhanced formulations and the possibilities to standardize these products or treatment systems are always facing long periods of weathering tests. Extensive research was conducted to compare natural weathering with artificial ageing, using a scheme based on two cycle units commonly used for artificial weathering and intermediate low temperature exposures. Statistical analysis of test results showed good similarity between both natural weathering and Xenon ageing
J Van Acker, M Stevens, M Nys


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