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Harriette Purchas gravatar image

On the fronds I suggest as soon as reaching maturity and that they can be dried and "woven" like a cadjan you could use. I have found no specs but will look in the next days (in fact i am in Manila next week). A caution is that for example in Sri lanka cadjan (basically coconut frond) is not supposed to be used in municipal areas due to vector / malarial risk (there is a relevant bylaw but I do not remember it) ... just a caution .

On the timber I can assist a bit more with an "edited" extract from a report I wrote for donor last year in Sri Lanka that may give some guidance. This however was for more permanent construction than emergency construction so could be relaxed accordingly.

"............................ Alternative Species, Grading and Materials for Timber Applications Alternative species are being sought but even these options are limited and expensive. There are restrictions on the milling of coconut as plantation crop, however, after 60 years it is considered to have reached the end of its useful economic life and can be milled for timber - though only generally the bottom one third to one half of the stem is usable structurally. Substantial quantities of coconut timbers were used structurally after the tsunami, though it is not preferred by the beneficiaries.

The FAO refers to the traditional use of coconut in Sri Lanka: “………In countries where processing of coconut wood was traditional (Sri Lanka, India, Zanzibar), coconut wood has been used as rafters and beams for roofs of buildings, window and door frames, and boat building. In Sri Lanka, coconut wood rafters …. ridge plates (ridge rafters) … are also made when old, large-diameter coconut palms are cut down……. The price of coconut wood rafters is about 30% of the price of conventional wood used for roof structures. There are many houses and buildings in Sri Lanka with roof structures built of coconut wood that are still in use after 100 years. These are special cases where the bottom one third of the stem of very old trees have been used without any treatment. In most cases, particularly when the middle third of the stem is used for roof structure, a preservative such as ‘solignum’ is applied. In some cases, used engine oil is used as a preservative to reduce cost……..”

In local studies in 1997, anticipating the need for alternative timbers it was suggested that alternative species might include Coconut (Cocos Nucifera); Cypress (Cupressus Macrocarpa); Eucalyptus species (Eucaluptus Grandis, Eucalyptus Pilularis, Eucalyptus Robusta, Eucalyptus Microcorys, Eucalyptus Citradora, Eucalyptus Globulus); Ginisapu (Michelia Champaca) and others. A number of these are considered in the earlier paragraphs above.

The State Timber Corporation (STC) of Sri Lanka currently propose Saligna (Eucalyptus Saligna) as an alternative to Jak, Palu, Eta Thimbiri, Dun. for structural application timbers (beams, rafters, ridge plates, wall plates and purlins / reepers) and Microcoris Grandis as an alternative to Jak, Teak, Milla, Keta Kela, Path Kela, Koon for window and door frames.

It should be noted that a number of commentators (as above 1997 and the STC), and increasingly common practice is in the use of eucalyptus species. Eucalyptus has positive attributes including as an efficient biomass producer, it can produce more biomass than many other tree species. It also consumes less water per unit biomass produced than many other species of trees. However, it has reported environmental cautions.....................................

......................... A further element in using alternative timbers such as coconut, is that they may need antifungal and pesticide treatment to maintain durability. The treatments utilised should be very carefully selected. Compounds such as CCA and CCB have been restricted in a number of countries and while their advocates indicate they are inert for humans after treatment, considerable investigation of treating softwood substitutes for local hardwoods in the Aceh tsunami response indicated that these and similar compounds should be treated with caution, and particularly offcut lumber should not be burned due to the potentially toxic fumes.

Additionally where lower grades of timbers are used, the design of the house should be appropriately modified - for example rafters may need to be a larger cross section, or more closely spaced, or even braced. Recognising that their strength and deflection will vary from the traditional timbers, with appropriate compensation in the designs, lower grade timbers may be utilised. It would be important to disseminate this clearly to beneficiaries so that they are more willing to consider the alternatives as a “cost trade off” and to ensure the appropriate design modifications are effected. ......................................

Additionally where beneficiaries are undertaking to cut and / or mill their own timber it should be borne in mind that uncured timber typically suffers quite a high degree of creep and deflection when loaded and additionally displays significant incidence of formation defects (twists, warps, splits, cupping, shakes, etc.). Poor curing especially when improperly stacked can increase the timber wastage. It is felt the approx. two to four weeks from cutting and milling local timbers is wholly inadequate for effective curing. It was also reported in the ** programme that one of their recurrent defects was sagging roofs due to the use of uncured timbers. As result it would be ideal if the programme advocated and facilitated that as soon as a beneficiary is formally accepted into the programme they should without delay secure their timber - either as a timber permit and arrange cutting and milling, or ensuring that merchant supplied timber will be cured. By actioning immediately on beneficiary approval, timber should at least have several months to cure before being incorporated into the roof. This may not entirely cure the timber but will assist and may minimise defects in the timber, and /or in the completed house roof. .................................." Regards, Tom