five sided ridge beams

HI Everyone;

Does anyone know the origin of the five sided ridge beam? I have seen several here in Mid-Coast Maine, both in rafter-purlin and common rafter roof systems. I know they are common in the Connecticut River Valley.

Are they always hewn? When did they go out of style?

Thanks;
Jim

Well what is it? Is it a ridge where the rafters connect perpindicular to their pitch? Does it look like a pentagon where it is pulled at the midsection down? I definitely don't know the origin but I am interested in it nevertheless.

Wait a minute all ridges have five sides.

Hi MO;

I am sure I need to provide a drawing or photo to fully explain a five sided ridge, but I do not have time to post one right now.

I am talking about frames which have a ridge beam, not a ridge board, into which the tops of the rafters are tenoned and pegged. The essential timber framer's joinery reference book Historic American Timber Joinery gives a discription on page 38.

There certainly are an amazing number of variations of how historic timber frames were built!

Jim

Not all ridge beams have five sides, a four sided beam will work, two roof planes and two rafter joint faces....
I've cut five sided ridge beams on my sawmill before...

We have cut pentagonal ridge beams where one plane followed level, two planes were plumb and the remaining two planes followed the slope of the roof. Unfortunately I don't have a decent picture with detail that I can post.

And I have seen drawings where two faces of the beam were perpendicular to the rafter slopes rather than plumb. To my thinking this would be preferred ... cut square whenever possible.

Hi

Here are a picture of a four sided (diamond) ridge beam in a house in Warren, Maine and a five sided ridge beam in a barn in the neighboring town of Waldoboro. Both buildings were built in the 1790s.





Notice how the diamond ridge ends but the building keeps going. This is an unusual roof system in an L shaped house. The only reason I can imagine to mix the roof framing was to handle the hip and valley framing with the ridge beam and frame the rest the easier way, with rafters which meet at the top with a lap joint.

The ridge beam in the barn has some wind braces between the ridge and rafters.

I have only seen about six or seven old frames with ridge beams and they have always been hewn.

I think frames with ridge beams are more difficult to raise (and disassemble) which is why I want to know more about them...Anything harder than it had to be had a reason.

Jim

Hi

Here are two photos of ridge beams. The first is a diamond shaped, four sided ridge in a house in Warren, Maine. The tops of the rafters are cut at an angle to match the ridge and the tenons angle upward slightly to be perpindicular to the edge of the ridge.

Note the ridge beam stops but the building keeps going. This is an unusual example of mixed styles of roof framing within the same frame. There are three common rafters which join with a pegged half lap at the peak. I think they used the ridge beam in the middle of this L shaped house to handle the hip and valley framing.



The second photo is a barn in the neighboring town of Waldoboro. There were twin 30 x 30 barns and the house were all framed with five sided ridges and common rafters. Note the wind bracing from the ridge to the rafters. I think this is the only advantage of having a ridge beam... to have bracing in the roof.

All of these buildings date from the 1790s.



I have seen rafter/purlin roof systems with five sided ridge beams too.

Jim

Maybe the five sided ridge was this way so there was not a compound angle to find between the brace and ridge. If the sides of the ridge were plumb then that the angle of wind brace to ridge would be a little bit trickier to find. Also, it seems that if the pitch is anything but 12:12 the five sided would have to be used in place of the four sided. Thanks for the pictures.

mo

By the way, how the hell did they raise this frame? The one with the five sided ridge.

Hi Mo;

I imagine they assembled one side of the roof, tipped it up and then inserted the rafters and braces for the other side. This is one of the reasons I am curious about the origin and motivation behind the five sided ridge beams...our forefathers had to be motivated to use these ridge beams.

There does not seem to be much written about them.

Jim

housewright --

I can see 2 reasons to frame this way.

1- To allow the use of wind bracing when there is no purlin to brace to.

2- More importantly, the use of a ridge beam facilitates scribing the roof planes as 2 separate units and keeps you from having to scribe each rafter pair seperately -- it's a time saver in a scribed frame. There may even be a way to tumble all the commons -- that would really save time.

As for the 5 sided ridge it allows the tenons of the rafters to be more or less sqaure -- much easier to scribe than if the ridge had plumb sides.


Gabel

hi anonymous and all on this thread:

I am familiar with one structure at UCV (Upper Canada Village) here in Ontarion Canada, that has this type of roof framing used, and it was in a general store type building. It dates to about 1784--1820--it also has the wind bracing framed in nicely with good workmanship.

I got to say right here that I am not certain that this is wind framing, but might rather be bracing that would hold the unit square during its subsequent raising. If wind framing was necessary why is it not used in other\more structures of this period?
As you think about it it appears to me that this type of roof framing required some baces to stabilize it before the roof boarding was applied --what comments are out there?

I have pondered over such questions as how the roof framing was raised also, as well as other types of structures such as the plank and frame buildings of which there are a few around here, and which needed a special type of technique for the raising

In both of your examples I believe that one side of the roof was assembled and raised with the help of a group of men using pike poles and arm power. when the one side was up to its proper height it was braced off and secured.

At this point the individual rafters on the opposite side were put in their respective mortises and secured working from the one end of the roof to the other, inserting the (wind bracing?) as they went.
I really see this as not being a real complicated raising but just in its proper order, and under good leadership.

The diamond shape of the ridge in the first example I believe from what I can see is as follows, on the one side the ridge is square to the ends of the rafters, this would leave the upper surface of the ridge in the right plane with the top of the rafters.
The other side of the ridge appears to me to be shaped similar but the ends of the rafters are set into the ridge on an angle, and the top of the ridge has been adzed off to the the same plane as the top of those rafters, this all to accomodate the pitch of the roof.

Normally the early roofs were a 1\2 pitch and the rafters would have intersected the ridge at a 90deg. angle. In the first example the pitch of the roof seems to be less than a 1\2 pitch and created a problem with the rafter seatings at the upper ends

It is this type of detail that is very interesting and to recreate even more interesting, and I must say, using my dear friends the Lovely Rough Hewn timbers.

great topic
NH

To reply to my own post, I talked to Randy Nash about five sided ridges and he said no one knows the origin. This is an opportunity for all of you barn investigators to travel to England(?) and track down the existance of anything similar to a five sided ridge.

Since starting this thread I have seen another ridge beam in an 1810 cape. it is in a rafter/purlin roof and the braces are long enough they interupt the purlin: the purlins are nailed to the braces. There is an endless number of variations of traditional timber framing!

Take care;
Jim