One of my indulgences is taking time to look at a detail in an old house and trying to get into the head of the craftsman who made it. I can’t say that every try is successful, but when I do figure it out there have been some great “Aha!” moments. More than a few times it’s taken years and some other discoveries to see what was going on.
Sometimes it’s a structural choice; how were two pieces of wood joined, why was that support here and not there. It could be material choice or why did that window go into THAT corner. Sometimes there’s a really good, smart reason, other times it’s tough to figure and there are some clear mistakes. These are lessons that are sitting right there waiting to be learned and many of them are still applicable today.
One important thing about successful (surviving) old buildings is that they could dry out if they got wet. Quickly too. And that’s the important part, if wood stays wet it rots. If it dries quickly it’s fairly forgiving of some periodic wetting. If you let it get too wet too often your building won’t survive for future generations to see how stupid you were.
How did they dry and are there lessons about that for today? They dried because of lots of air and energy flow and materials that don’t trap moisture. No insulation and free air movement in wall cavities are a recipe for drying. Interior horsehair plaster dries very rapidly which also helped keep the walls dry. Of course in the 18th & 19th centuries showers and hot tubs were in short supply and indoor swimming pools were even rarer. So buildings had lower moisture loads to deal with and had good drying potential. That’s a good way to make a building that will last.
We have become more regular in our hygiene, and with higher energy costs we want insulation in our walls and ceilings. This puts us in a bit of a bind because we just messed up our building longevity strategy. What to do? Let’s go back to our original building and see what else we need to change. Well, if the walls won’t dry, maybe we should keep them from getting wet. Some of those old details will still work for us and some won’t. If we are expecting better thermal performance we need to give the walls (and other building parts) better water management so they can make it to the next generation and beyond.
With future posts I’ll explore the details, but new construction will have different solutions than rehab, probably. With rehab or retrofit you have to think more carefully about what the strengths and weaknesses of the building are, what the extent of the planned work will be and what can realistically be done within those constraints. The reason I love working with older buildings is that I can use all those lessons I mentioned earlier and, with luck, get some more.
Oh, one more thing. When you do undertake a rehab on an old building remember to leave a penny dated the year you completed the work where someone will find it when they get around to their own project in the future. They’ll know that you were thinking about them and maybe take the time to learn a few lessons of their own.