I get asked this question a lot, short answer … Yes. But there’s a reason so few contractors use overpressure (or pt) treated redwoods for mud thresholds and bottom plates.

First, let me tell you that I have remodeled homes in areas of San Francisco and Marin that are over 100 years old, built entirely from redwood, and are still structurally sound. This is because redwood is naturally rich in acids, which prevents rot and prevents insects from eating it, since those are the two worst enemies of houses, redwood makes sense. Until you look at the price tag. The fact is that many areas of redwoods were overexploited and those that were not are now protected. As a result, the price of redwood is very high compared to other truss products and they are now using younger growing trees, which equates to more knots, twists and tails.

So, to cut costs, pressure-treated lumber was introduced as a lumber that could mimic the attributes of redwood, but at half the cost. Pressure-treated lumber is typically Douglas fir or sometimes hem fir and is injected with many toxic chemicals (copper or zinc napatan are the most powerful). These chemicals are what prevent rot and pest infestations, but they are also known to cause cancer by contaminating groundwater when disposed of in landfills. In California, pieces of waste pt must be disposed of in a biohazard disposal facility. Recently, toxin levels have been reduced by approx. fifty%.

It is also worth noting that it is never acceptable to place untreated Douglas fir lumber in direct contact with concrete. There are several ways to treat Douglas fir yourself and make it resistant to pests and rot. The form n. 1 to do this is to apply copper napatan in a spray can or in a regular liquid for brushing. You can find this at just about any neighborhood hardware store, but be careful doing it! It will stink bad for a day or two, so don’t apply it directly to living spaces. Be sure to read each and every factory instructions regarding the application of any sealant or product to prevent rot.

So to answer the question, yes … absolutely, redwood is a great product for mud thresholds. But if you are going to use redwood save yourself some money and get ‘rough cut’ lumber, this will be a bit larger so you will have to cut it widthwise but the price difference is worth the extra work.