I built a decking in May this year, no problem with the build at all. Just the knots in the decking are oozing what I think must be sap, which sets as white powder after drying. Is there a way I can stop this, or at least lesson it. Asked in B&Q, they recommend brushing with turps, but to be honest they weren't sure, oh and a comment I should have picked the deck boards without Knots..There having a laugh, I bought 45 x 4 mt boards for delivery, so no chance in that, besides I haven't seen many knot free boards. I did give the deck two coats of Screwfix clear decking oil straight after completing the deck. Any advice appreciated.