They don't build 'em like they used to...

In the process of installing the bathroom ventilation fan we cut a hole in the house (this is not the interesting part).  Much to our surprise we discovered that the house is sheathed in ~ 1 1/2" solid oak boards:

Cross section of the oak sheathing

We already knew that the back hall portion of the house had solid wood construction.  During installation of our new backdoor the carpenter cut out some very impressive 2" oak boards.   At the time we assumed that this had at one time been perhaps a passage to a barn or woodshed.  Little did we expect to find this type of construction throughout the house!