This weekend when we installed the microwave we had to cut into the wall to install the exhaust vent. And there was the brick. Large clay bricks. It was pretty cool. They were all different sizes, and have marks on them from when they were formed. And some still have some dried plants on them (like grass) which is most likely from the bottom of the pond/lake where the clay came from.
As cool as this is, R and I (in all of our old house research and schooling) have never heard of this. Brick has no insulating value... the house is post and beam, so the brick isn't structural. What's it there for? My guess is as a fire block.. to keep fire contained either inside the house, or keep it from getting inside and spreading. R thinks it's to keep out stray arrows and bullets. Not sure how serious he was with his guess.
So I did some research. Turns out I was right. But that wasn't the only reason it was used. According to www.inspectapedia.com, bricks in pre-1900's homes were used mainly as an air-infiltration or wind barrier, kind of like an early insulation (even thought brick has basically no r-value). Brick also helped cut down on sound and contain fire, especially if the house was balloon framed (which ours is not, thank God). This explains a lot. Our house is very good at keeping cool in the summer (not as cool as an air conditioned house, but cool enough to be more comfortable than it is outside), and retains heat pretty well. Despite there being no insulation in the first floor walls, I never feel any drafts at exterior walls (the front door yes, but that's another story), nor do they feel cool to the touch. Houses built today have plywood sheathing underneath the clapboards, as well as an air-infiltration barrier. Our house has the clapboards nailed directly to the posts/studs.
This was called "nogging". The bricks were never meant to be seen, hence the rough, irregular shaped bricks we found. According to the site, brick nogging is most common in houses built between 1810 and 1900. Our house pre-dates that by almost 40 years. The brick in the walls could also be the reason that we have almost no electrical outlets on exterior walls.
Another interesting characteristic of homes with brick lined walls is sill damage due to the extra weight (estimated at 400 lbs PER framing cavity (roughly 16")!!). Our sill damage is due mainly to past insect damage, but perhaps it got so bad because the insects started eating away the beam, and then the wall became too heavy for the damaged sill, and it quickened it's demise.
The weird thing is that all of the pictures I'm seeing of nogging show significant mortar joints. Granted that these bricks were put in quickly and without much care, but we don't even have any mortar! At least not that we can see. All of the bricks we found just seemed to be piled on top of each other, with nothing holding them together other than gravity!
This picture (from rasala 1234 on flickr) is the closest I can find to what our walls look like.. Just bricks. Pretty cool though!