I saw the pine tar pit at Turkansari Outdoor Museum near Oulu in Finland and was taken aback by the diameter of pine tar burn pit. They make pine tar sweets from this gunk which are apparently good for sore or stripped throats. This pine tar was imported into England and used to coat wooden ships plus I have also seen it used on the lower parts of timber framed buildings (brick & sills). Part of the front door of our granary is coated with this tar with later planks simply being covered in creosote.
The Danes and Vikings occupied large parts of England (Danelaw) long before the Normans came calling and so its quite possible that a significant transfer of carpentry know how arrived in England from this source.