Tallowwood has a relatively high tannin content but is an excellent choice for outdoors. If possible, lay the flooring parallel to the external wall rather than by the usual method, which is at right-angles. Then it is only the outer boards that will be subject to weather exposure, rather than the ends of all the boards. Also it's important not to cramp the boards too tightly together so there is an allowance for a little expansion if they get wet. Regarding removal of tannin, we suggest you use one of the products described as 'tannin and oil remover' - you will find such products on the net. We don't endorse any particular brand since we haven't tested any, but we assume they perform as claimed by the manufacturers. Each product will have directions for use. We doubt the boards will cup from wetting during the cleaning process - tallowwood is quite a dense timber which only takes up moisture after prolonged wetting. Timber doesn't spontaneously release tannin, but only when water (eg rain) strikes a bare surface and washes the tannin out. So if you think rain will reach the underside it might be best to treat both sides of the boards.To dry the timber after treatment, stack it flat with spacer sticks between each layer so air can circulate through the stack. Avoid putting it in the sun while drying. Regarding a finish, we suggest decking oil once the timber has thoroughly dried.Tannin removal
Answered on 13-04-2021
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