Wider use of timber has the potential to greatly reduce the embodied carbon of construction. Improved chemical treatment could help overcome some of the barriers to wider application of timber, by furthering the durability and/or mechanical properties of this natural material. Improving timber treatment by treating the whole volume of a piece of timber, or tailored sections thereof, requires sound understanding and validated modelling of the natural paths for fluid flow through wood. In this study we carry out a robust analysis of three-dimensional X-ray CT measurements on kiln-dried softwood in the presence of flow and identify small portions of early-wood which are uniquely capable of transporting fluids-herein 'efficient transport pathways'. We successfully model the effects of these pathways on the liquid uptake by timber by introducing a spatial variability in the amount of aspiration of the bordered pits following kiln drying. The model demonstrates that fluid advances along these efficient transport paths between 10 and 30 times faster than in the remainder of the timber. Identifying these efficient transport pathways offers scope to improve and extend the degree to which timber properties are enhanced at an industrial scale through processes to impregnate timber.