Wednesday, July 31, 2013

Kingsmere Walling Workshop - Part 1

I returned last weekend to teach another workshop just outside Ottawa at the historic Kingsmere Farm, original residence of Prime Minister Mackenzie King.

I was asked to repair this section of wall (?) that you see here.

The stones looked very round and awkward to work with and completely uncooperative.

Nevertheless despite extreme heat humidity and rain we completed the task of building a beautiful wall. Stay tuned to see how seven enthusiastic students and their instructor tackled the project. 

Monday, July 29, 2013

Bridge Number 13

I figured I'd play it safe and have bridge number thirteen be a much smaller bridge than Crown Bridge and the previous eleven dry stone bridges. 

So I built this one for Ray and Barbara at their house in Alton, Ontario after the 2013 Canadian dry stone wall festival.

Friday, July 26, 2013

Building a dry stone bridge- Part 16

Here is a photo Trevor Spik took of Crown Bridge about an hour after the form was pulled out.

The total length of the bridge is about 32 feet. It has a nine and a half foot span and it is 5 foot 6 inches wide. The height from the stream to the bottom side of the vault is about four and a half feet.

 It was a great pleasure to build this bridge for a long time client of mine who happens to be a dentist. Normally it's the dentist who tells you that you need a bridge, not the other way around. So anyway being my dentist friends bridge is also why we decided to call it Crown Bridge.

Lots more pics to show you of this bridge tomorrow.

Thursday, July 25, 2013

Building a dry stone bridge- Part 15

We could almost hear the gasp of relief from the form as it is released of the duty of supporting over ten tons of stone for the last two weeks. 

The form was lowered several inches by chain sawing and then knocking out a few of the cedar logs in the crib that was supporting it. Two of us were then able to slide the form out.

Wednesday, July 24, 2013

Building a dry stone bridge- Part 14

 After the gravel has been applied landscape fabric is rolled over the footpath.

Then a covering of clay soil is added...

Then a layer of top soil...

Then rolls of sod.

We still haven't taken out the form yet.

Waiting until tomorrow for the client.

Tuesday, July 23, 2013

Building a dry stone bridge - Part 13

In some of my photos of the building process, it appears that the two springing points of Crown Bridge are the same height. In this photo of the side of the bridge having all the copes now completed, you can see that the right side of the arch starts much higher than the left.

The voussoirs stick up in a jagged pattern above the line of the arch. These protruding rows are thoroughly pinned with thin shims to tighten the whole network of radiating stones in the vault. 

A covering of medium sized stones are then laid in place above the mesh of voussoirs and shims.

Then a  3 inch layer of 3/4 clear stone is put over the entire walking area between the copes and smoothed to create the base for the path.

Monday, July 22, 2013

Building a dry stone bridge - Part 12

My good friend Norman Haddow dropped by for two days to lend a hand on Crown Bridge after flying in from Scotland to attend the 2013 Canadian Dry Stone Festival .

He and I worked on the first section of square upright coping.  Vertical coping is Norman's specialty. It is straight and level. Even a quarter of an inch difference in height of individual copes can create annoying jogs in the profile of the bridge, so we had to take care that each cope was shaped properly and fitted in the right sequence along the top of the stepped side walls. 

Norman has helped with three of the 12 bridges I have worked on here in Canada.

Sunday, July 21, 2013

Building a dry stone bridge - Part 11

The shaping and fitting of the builder stones in the skewback to the springers and voussoirs of the extrados of the stone bridge are very important to have looking right. The horizontal stones have to meet the radiating stones nicely for the bridge to look appealing. This is a sketch on a stone I did for Trevor illustrating the point.

This is the north side of Crown bridge before we started adding parapet coping.

Saturday, July 20, 2013

Building a dry stone bridge-Part 10

Tapering of individual stones? - It's interesting to see how few tapered stones there are, and how minimally the ones that are tapered are.

Friday, July 19, 2013

Building a dry stone bridge -Part 9

Pre-shaped outer voussoir stones ( essentially, corner stones ) and inner voussoirs (any good parallel-planed, flat faced 'builder stones') are fit carefully together  laying them in courses over the wooden form. Each row of stones is supported by 2 x4s suspended over the ribs of the form. The 2 x4s are placed loose on the form as the courses are added making it easier to stand inside the form until the last few courses are set in place. These 2x4s will be easy to remove when the form is lowered slightly, making the centering much lighter to carry out from under the bridge.

Thursday, July 18, 2013

Building a dry stone bridge -Part 8

Springers are shaped and wrestled into position.
Their bottoms are level. Their tops angle to the centre point of the circle about two feet below the form.

Yes a couple were 'sawn' but a lot of them were 'hand-dressed' from springer-like shapes found in the tons of stone we brought down to the site.

Oh, did I mention the poison ivy everywhere ?

Wednesday, July 17, 2013

Building a dry stone bridge - Part 7

 Most bridges span from piers that are the same height. The creek banks here had a height difference that required the segmented arch form to be supported at an angle of about 15 degrees.

I have wondered about this before but never tried it until Crown Bridge (bridge number twelve) - that is, if tilting the circular centering to accommodate a change in height makes much of a difference

Will the slight rotation compromise the structure of the vault ? You tell me.

Tuesday, July 16, 2013

Building a dry stone bridge -Part 6

The five foot deep foundation holes are built up with large material to make peers below grade. Side planks make temporary bridges to transport building material over the creek

Each layer of carefully fitted foundation stones is hearted with stone chips and gravel around the joints, being careful not to have stones wedging gravel between of the stones above and below. That would make the gravel susceptible to acting like marbles and causing the stones to roll sideways.

A crib of cedar posts is made in the creek to support the form

It looks like a mess, but it's a very controlled mess.

Monday, July 15, 2013

Building a dry stone bridge - Part 5

The holes for the bridge foundations have to be dug more then four feet deep and five feet square.

First we have to dig through a network of tenacious roots, then stony soil( that resists every thrust of the shovel) and then we hit hard clay . After a few more feet water begins seeping in and it starts to get pretty muddy down there

The next day we need a step ladder to get down into the hole in the morning to bale it out so we can continue to dig deeper.

After two days of digging in ridiculously hot humid weather we're ready to start laying stone.

Sunday, July 14, 2013

Building a dry stone bridge. Part 4 The Solitude of Stone

Consider the solitary attribute of stone.

Unlike other more fluid, cohesive elements like fire water and air, the basic quality of stones is their detachment. 

Stones keep their individual shapes and sizes ferociously. They keep their distance too, even when they are collectively compressed together tightly by their own great weight.

It is this dispassionate 'disconnectivity' which makes them very useful for building with. The very thing that keeps a dry stone bridge or arch together is the the solitary resistance of stones to becoming 'attached'. 

Stones don't merge . While a slurry of Portland cement, aggregate and water will eventually harden to become a single stiff lump of concrete matter, stones properly fitted together dry create a structural network that not only has dynamic strength but the capacity to yield. 

Bridges of steel and wood are physically fastened together. The various materials 'tug' on each other and as long as they continue to stay 'bonded' the structure stays together . 

By contrast, it could be argued that the stones in an dry laid arch stay up by repelling each other.

Friday, July 12, 2013

Building a bridge. Part 3 - The solitude of idea.

An arch is an amazing thing. I've built a number of dry stone bridges and vaulted structures and I still find the whole arch building thing quite magical. Every arch starts as an idea. Every arch is unique. Up until the moment it is completed (and the form is taken away) an arch exists as a concept in the solitude of the mind. 

This arch stands in the remoteness of an Alaskan mountainside. It was built by Akira Inman recently while participating in a two week climbing course. The arch is now more than an idea. It is more tangible - it is a real thing. As it is probably very close to what Akira had in mind, it becomes a kind of creative bridge allowing us to get nearer to what he imagined. This creative 'closeness' is the accessible counterpart to the original solitude of the idea. 

Wednesday, July 10, 2013

Building a dry stone bridge. Part 2 - The solitude of place

What property having a stream or small creek on it can't be improved by a dry stone bridge ?

This wooded valley behind the clients house is no exception. The site is a perfect setting for a small footbridge to enable the new owner to get to a previously neglected apple orchard in the open area beyond the woods that he wants to tend and prune.

However there are a few problems to overcome building a stone bridge in such a secluded spot. The solitude of the site requires bringing in most of the stone by wheel barrow and large tree dolly. 

Another issue to consider is that the spot where we are to build the bridge is approximately 30 inches higher on one bank than the other

Big machinery will not be able to get down the foot path to the bridge site, so digging the foundations makes it a labour intensive project from the get go. Trevor and Colin are better than a big old excavator any day.

Tuesday, July 9, 2013

Building a bridge Part 1,

A dry stone bridge is the merging of three solitudes

The solitude of place

The solitude of idea

And the solitude of stone.