Roof Within the Roof

Our house with lowered roof line to match original pitch.

I think the configuration of our house looked like this(ish) in 1860 when it was  moved. The back part of the house was probably a kitchen ell and the roof was very low pitched. I'm guessing that the new, higher pitched, common rafter roof was added around the time it was moved. The new roof line was much higher pitched than this.

I have moved (badly, I know) the roof down using Photoshop to the pitch of the underlying roof frame to get a feel for what it might have looked like before the new roof was added. I have also taken out the addition that was added sometime in the first half of the 20th century above the ell.

Sometime in the first half of the 20th century an addition was added above the kitchen ell. The addition was built as an apartment for the then-owner's mother.

Peeling the Onion

Here is a look at the outside of the inside roof. Follow me? Within the above addition above the ell there is still the back of the older (circa 1860) roof. It is frozen in time. The wooden shingles are still on it and the two chimneys, one on each side, are still there inside the addition.  

It gets better. This is the turducken of roofs. When you go into the above hole in the old roof, you see this:

It wasn't until recently that we came to realize that what we were looking at here was another roof. Looking at it now it seems so obvious, but because the pitch is so so low, it seemed much more like some sort of structural support for the common rafter roof, above it. 

The low-pitched frame has purlins which are horizontal beams that run along the length of the roof, notched into the main (common) rafters. You can see them overlapping in a cut made in the major rafters. The "new" common rafter roof is braced right on top of the old roof. Because roof framing is often a good way to figure out some features of the original layout of a house, this roof gave me a good opportunity to try to figure out where the fireplace(s) were. 

 

I used to think that our house was originally built as a "twin rear-wall chimney" house, meaning chimneys on the back walls (to be distinguished from gable end chimney houses of the more southern and mid-western hall and parlor plan) since that's where the stove chimneys are now.

 From Sightseeking: Clues To The Landscape History Of New England, By Christopher J. Lenney

Then we found a boarded up window peeking out from behind the left chimney on the second floor and evidence of a door behind the first floor chimney on the same side. I realized that a center chimney may have been more likely until I looked at the attic floor and found that there is accordion lath there too so there was not likely to have been a central chimney. 

First floor stove chimney built in front of original back door.

I can not tell you how happy I am that whoever replaced the roof didn't remove the old one. I am endlessly fascinated by this thing. The more I learn about timber frame construction the more it reveals to me.

According to Hugh Morrison's, Early American Architecture from the First Colonial Settlements to the National Period, there is an important distinction regarding direction of the sheathing boards and the number of rafters present. Although the sheathing boards are missing, the purlins and rafters reveal something about the date range of the roof:

 

I had wondered why our old roof frame had so few rafters (the vertical beams)- it seemed like too large of a gap between them based on other roof frames I have seen. So the explanation for this is that our roof was designed for horizontal, not vertical, sheathing boards and shingles and not based on the thatch-roof design. There are still mostly just mysteries to this frame, though. One of the mysteries is this missing purlin.

If you look closely at the area that is circled you can see where there is a missing purlin. The photo below shows it closer up although it's a terrible picture. The missing purlin could be evidence that the wood for this frame was reused or that the house was at one point attached to another building (possibly part of the ell of Rev. Sherburne Blake's house?)

And, am I crazy or does the top pitch look like it's meant to house another rafter? This "step" is only on this side, not the other. Reused wood? I have no idea.

Our house was at least partially built using what is referred to as scribe rule framing. I know this because of the "marriage marks" on the roof frame below. Here is an explanation:

 In scribe-rule framing, the joints in one timber are custom cut to fit the joints in a second timber. The carpenter uses specialized transfer tools to transfer the dimensions, along with any irregularities in the first timber, to the second timber. These marks, known as “marriage marks,” ensure a tight joint. Even though timbers may perform the same function, they aren’t interchangeable when this method of framing is used, because the connection between each pair of timbers is unique. Scribe-rule framing is useful when joining hand-hewn timbers that aren’t uniform in size.- Colonial Wall-Framing Methods

Marriage marks I found on the girts in the basement.

Written by Kerry Baldridge