A good many years ago I had professionals paint the wood trim on the first floor of my house, which is fieldstone, and put "water repellant /stain" on the shake shingles which are on the 2nd floor. The paint didn't last more than 5 years and began to peel (Sherwin Williams), so I repainted the trim myself using Valspar, which has lasted close to 10 years already.
My question is what kind of "water repellant / stain" do I use on the shake shingles? Oil base? Water base? The home is 90+ years and they are in good shape and Id like to keep them that way. They have not been painted and I don't want to paint them. What would be the best application for the water repellant / stain? Would Thompsons water seal work? Someone told me to use a "marine" grade water repellant. If that's what I need, where would I find it?