Hi everyone on this most interesting topic

The only thing that I can add here is that we tend to forget about water turbines many of which were about 45 horse power and could be driven with an 8 foot head of water. The horsepower increased with the head of water depth, but generally speaking the 8 foot head was a good rule of thumb, and was easily obtainable in this area, on side creeks entering the St Lawrence river water shed. These turbines started to appear about 1850 in this area and improvements were rapidly put in place.

They were pretty well located as a stationary power plant, not portable so to speak as a steam engine was

There was ample power here to drive a circular saw of say 5 to 6 foot diameter at a decent cutting speed. this speed of course was dependant on the size of the log being cut.

In my book it was hard to beat the steady power of water or steam, water being the cheapest of the two when available.

In mills the speed was steadied by the use of large flywheels that stored and delivered power as needed, acting like a governor so to speak.

Thanks Ken for helping this subject along.

NH

Don -

Connecting Girt framing did begin here in New England, Northern NE at that. And as I alluded to upthread, such framing seems to have been pretty much limited to Maine & NH, though I can not say for certain how common it might be represented on the west bank of the Conneticutt. I do know that the southern extent of the regional dominance it holds, stops almost dead on, the Mass/NH line. (I came up in a Merrimack Valley border town) Paradoxically, this seems to be the same range of geographic dominance in which, can be found, common purlins.

Neither stytem of framing seems to historically have spread beyond this regional range. I have long tried to research first, what influence/s drove to dominance common pulin roof systems (assuming some regional variation in Olde England played in - this seems not to be the case) And then, what might have influenced a region wide "paridigm" shift in framing. The change was abrupt, like the flipping of a switch, and I know of no other like it (I have been in but one building I would call transitional - having both jowled posts and CG's - and at the same time having seen numerous iterations of "transitional" stick buildings) The only other such related and rapid shift, I know of, was the one abandoning scribe and accepting Square Rule, though in its case the shift was not region bound, but continental in scope, but every bit as rapid. I know of no other area where the plate system was abandoned.

To answer your followup - Almost ironically, Yes, current framers work with these systems today. This largly due to authors from and influenced by this home region, having penned well read books which went on to heavily influence the timber framing revival.

And to speak to the sawmill side of this thread - Frames with the amount of hewing I describe above, are in my expierience, something of a rarity, NE seemingly blessed with good water (Horsepower producing head) saw the building of mills from early on, at least match, or (with intent) better the rate of the spread of settlement - The well heeled and connected granted the best mill sites -

This book/link suggests just how early -

http://books.google.com/books?id=MxILAAAAIAAJ&pg=PA6&lpg=PA6&dq

From a carpenters point of view, this variation of square rule, with connecting girts and common purlins, seems to further simplify the prefabrication process, which appears to be one of the primary criteria of square rule as opposed to scribe rule. (I am assuming that the common purlins are tenoned into the principal rafters of the trusses, and are flush with the top surface of the rafters.)
The design of the structure is now a series of regularly spaced bents. All the connecting girts and purlins are a common length.
This simplifies the cutting list and the actual cutting. There are now no long timbers to procure, or scarf joints to cut,just a large stack of equal length girts and purlins with tenons at both ends.
When it comes to rearing, it is simply start at one end and stop at the other, temporarily propping the first and second bents and then fitting the connecting girts and purlins. The next bent is simply repition of this procedure.
This variation can be viewed as reducing the design to a simpler modular format, that is still in use today in, using steelwork or reinforced concrete sections rather than timber.
It is fascinating and illuminating that this secondary leap of conciousness took place within a decade or two of square rule first emerging as a "new" framing system. It could be interpreted that once the scribe rulebook had been torn up that all elements of design were under re-evaluation.
These original designers/carpenters should be celebrated for their contribution to the evolution to the craft.

Sussexoak, I would assume the purlins would be drop-in or by by-pass purlins. Where the wall girts would of been tenoned. As a builder I cringe at the thought of having that many tenons to line up with the next bent coming on. You guys with these CG buildings in your area, what about the purlins? Tim

Thank you Will for the information. It has cleared up a lot. And that link to the history of lumber book is a great find!

And neat to hear contemporary builders are using this system today.

This "CG" (connected girt) system may be a northern New England practice as you say, but funny that TIMBEAL, who lives in Maine has not seen it before. I think Tim is in Washington County, right Tim?? (far eastern Maine). This helps illustrate how Maine is not the homogeneous state many believe it to be. The state differs greatly north and south of Bangor (you wont find the "Maine accent" north of here)... and I think that's largely true as far purlin systems go too. Can you comment Tim?

As many know, the north of the state is French-Canadian, the south is English in terms of settlment patterns. Bangor is a good dividing line.

Tim, as far as the purlin systems in these CG barns I've visited, the purlins are flush w/ the top of the rafters. In fact, the latest one, which is supposedly dated to 1880, has a sawed frame, yet the purlins (and only the purlins) are hand hewn...

I agree that lining up that many tenons for the next bent must be alot to handle. Makes me think the purlins have just a haunch set in a pocket of the rafter and not a true mortise and tenon like the girts in the walls.

I'll have to go back and look at some of these.

may the education continue...

Don

Hi Don, North or South or maybe I am East of Bangor, the weather man never knows. I have never thought of coastal down east Maine as being French Canadian but have thought that of northern Maine "The County". There is a 3rd part of Maine, the Eastern part, which is often over looked. My home town of Jonesport/Beals has a thick accent and if you trave 20 or so miles toward Canada it completely changes. Sort of like frame details.

I have not seen any CG bent typologies here. That doesn't mean they are not here just not discovered yet. I am looking. Are there any pegs at the purlin/rafter joint? Tim

Tim,
yes, eastern maine is a bit of an anomaly. And not FrenchCanadian. I have read that purlin frames are typically not found in the northern part of our state... Roughly above Bangor. Can you confirm?

Of the 4 "CG" frames I've seen here in southern Maine. One clearly shows pegged purlins. The others aren't as obvious. One that was restored had new purlins put in and they were spiked on. I'd have to go back and check on the others. And I will some day in the near future...

By the way, dovetailing the purlins into the rafters would be a neat method.

thanks--

Don

My assumption of tenoned purlins, was based on contemporary English carpentry, so it will be interesting to find out if this detail was retained in the "new improved square rule" or if the purlins were all housed. Presumably there must be some fixings between at least one of the purlins and the rafters to prevent the other purlins falling out of their housings.
How closely spaced are these common purlins? about 4 foot apart or closer?

I was putting off replieing in hopes that someone else from common purlin land might pipe in...

It would be kinda cool if the forum could be used almost as a research tool, and some greater sense of the extent of the range of dominance and varitions of historical example might be posted.

But I'm thinking there are too few regular posters or even lurkers from the area for any patterns to emerge...

There are three common variations I see most frequently, I'll start with what is probably the least common of the three, because it has a tenoned member, while tenons are used infrequently in CP systems. I've seen the term Major Purlin / Minor Purlin bantied about in print, to describe (if memory serves) this version, (though I've never used it in conversation) I think sussex Oak might know it as a Butt Purlin (on the road at the moment so I connot consult my library) I know the main tenoned purlin as a Principal Purlin (but that may be confusing to some in that this term is often used interchangebly with Purlin Plate)

In this variation a heavier (Say 6 X 9 on the flat) tenoned purlin is found at midpoint of the Principal Rafter - This almost always found with up & down wind bracing - Sometimes they are staggered up & down (to allow for greater tenon relish) - I have seen the occasional in-line example where two hi/lo bypassing tenons shared the same mortise.

Perhaps the most common variation has regularly spaced (40" - 42" - Memories not serving - I should know, but this is only an educated guess) purlins - These at first glance, appear to be individual pieces, (This is noticed most easily when round poles hewn on the top and adzed to square at the Principal Rafters are used as CP's) but often span multiple bays (two most commonly) and the breaks are staggered with intent - a technique which survived the transition to CG framing (and indeed became more important and necessary) - These purlins like the ones above and below the Principal in the above example, lap unbroken through a two inch deep dap in the top surface of the Principal Rafter.

There are examples from both sides of the transition which are broken at every bay. Like the ends of multiple bay purlins, two opposing laps share a dap. In both cases the rest/bottom of the purlin sits in a housing.

The last common variation, is found most commonly in earlier scribed buildings, and has staggered purlins sharing a common dap, with a short section (10 to 18 inches) for relish dropping down to full depth in the bay beyond. These also span multiple bays.

Don -- I have never seen a historical CP which was dovetailed, (Though they do drop in) but it was a common way of joining them early in the current revival.

Are the pegs you are seeing a single peg in the center of the rafter ? Or are there groups ?

Hi Will,

What's a dap ?

I agree whole heartedly that this forum could be put to much greater use and what better if "the archive" were opened to let us see some of the recorded frames and thus help illustrate the points that you make above. With posts such as yours maybe the peepers could be turned into contributors. Don has done a great job in encouraging us to examine and discuss this very interesting subject.

The outcome of this topic goes a long way to explaining (to me) why Ted Benson (NH) made use of the interrupted wall plate CG framing style illustrated in his first book. I never could quite understand why he did this when Jack Sobon's (western Mass.) books clearly exhibit a definite preference for continous wall plates. It now seems from your discourse above that this style of framing would appear to be both limited in range and date - just like our experience with some specific framing styles here in England.

By the way, SussexOak is none other than Joe Thompson - the Weald & Downland Open Air Museum lead Carpenter. Joe teaches the "timber framing from scratch" courses held at the museum and also lectures on the Bournemouth University Masters in Timber Building Conservation course also held at the museum under course Director - Richard Harris.

Regards

Ken Hume