Stevenson's harbour wall building technique

[dylanwinter]

I am reading a book about the Stevensons who built nearly all the lighthouses and many of the harbours on the East Coast where I am currently sailing

this is a snap I took of Anstruther Harbour wall

why have they laid the blocks that way?


www.keepturningleft.co.uk/wp-content/uploads/S1500018.jpg


Dylan

 

[JSYmartini]

The breakwater at Elizabeth Castle, protecting the entrance to St. Helier harbour is of a similar design. Built in the 19th century I think, must be a reason for it I guess!

 

[Twister_Ken]

why have they laid the blocks that way?



Dylan

Makes for more interesting reflections when there's a snapper about?

 

[oldbilbo]

I guess it'll be double ( or triple ) diagonal, just like many tough ply/epoxy hulls, and how some of the Royal Navy's hulls were constructed. That aside, the 'angled layering' projects weight of the blocks to the adjacent side, which helps in preventing the seams opening up under heavy wave action, as those seams would tend to close up under gravity.

 

[cliff]

Easier to handle (place) the blocks in that position and less tendency for the wall to bulge when the core is placed and compacted not to mention the inherent stability of the cross pattern. - those Victorian engineers really knew a thing or two - lost on the modern computer aided feckwit.

 

[penfold]

And no doubt all placed with the aid of nowt except shearlegs and the armstrong method.

 

[dylanwinter]

I do know that they used oak pegs to tie the blocks together

no idea what happens when the pegs rot

D

 

[claymore]

Well - once you have managed to tear yourself away and made it over to Gods Country, you must spend time around David Balfour's Bay where you can study the Stevenson methods at first hand.
Would it be Bathurst's book you are reading?

 

[dylanwinter]

Well - once you have managed to tear yourself away and made it over to Gods Country, you must spend time around David Balfour's Bay where you can study the Stevenson methods at first hand.
Would it be Bathurst's book you are reading?

well, Anstruther was built by the Stevensoons and I saw the harbour wall at first hand

so will I am looking forward to seeing the Stevensons there myself - theodolytes on shoulders


as for the Bathhurst book.....

I read about half and then slowed up

not sure if I will finish it

too much in it about family disputes and exhausted right hands and not enough about engineering for me

D

 

[John the kiwi]

Having laid a few blocks and bricks as an amateur i offer this surmise. With blocks laid flat you have to "batter" the vertical end with mortar and then apply enough horizontal force to squeeze the mortar.
Now all us amateurs know how hard it is to a) get the mortar to stay on the vertical end and b) tap the Block sideways into position without the block sinking and squeezing out the mortar underneath.
(Professional blocklayers have probably forgotten these things cos they do it so effortlessly.)
However with stones the size of your wall, easy peasy to apply mortar to the angled faces where it wont fall off before you lower the block into place and then when you do the weight of the block will self bed it into both the bottom and end mortar beds..

Clever those chaps!

 

[AntarcticPilot]

A rather different suggestion. I am given to understand that masons prefer to lay stone in the same attitude as it came from the quarry; apparently it weathers less quickly if you do that. Fine if your quarry has nice horizontal bedding planes, so you get blocks that lie flat. Most English quarries are like that. But in Scotland, it is entirely possible that bedding planes don't lie flat in the quarry, and of course, it is much easier to cut rectangular blocks parallel to the bedding (or cleavage or joint) planes. So perhaps the construction is a pragmatic response to the source of the stone?

However, I am quite prepared to be wrong - other suggestions sound at least as plausible as this one, and it may be that there is no single reason why Stephenson chose to do this. I am sure that, being a great engineer, he would have had good reasons!

 

[sarabande]

Having laid a few blocks and bricks as an amateur i offer this surmise. With blocks laid flat you have to "batter" the vertical end with mortar and then apply enough horizontal force to squeeze the mortar.
Now all us amateurs know how hard it is to a) get the mortar to stay on the vertical end and b) tap the Block sideways into position without the block sinking and squeezing out the mortar underneath.
(Professional blocklayers have probably forgotten these things cos they do it so effortlessly.)
However with stones the size of your wall, easy peasy to apply mortar to the angled faces where it wont fall off before you lower the block into place and then when you do the weight of the block will self bed it into both the bottom and end mortar beds..

Clever those chaps!

especially true if the blocks are properly dressed, (ashlar is the name).

 

[DanTribe]

Perhaps he was just that way inclined?

 

[CreakyDecks]

Might it not just be easier to slide the blocks down the previous sloping layer than to have to lower them down vertically?

 

[Twister_Ken]

Do the blocks follow the line of any rocks they abut at the landward end? Thus saving time truing-up that bit of Scotland.

 

[MM5AHO]

I've spent quite a bit of time exploring lighthouses on the west coast. Most of them Stevensons. Think I;ve only seen one pier made that way, so I don't think its a "Steveson trademark" type thing.
Here's a shot of the shore station for Dubh Artach...

Here's part of the pier at shore station for Skerryvore (near Tiree)

Here's a bit of the walkway to the lighthouse off the north tip of Mull (forget its name)

If I remember right, these all Stevensons, but various generations.

I found several errors in the Bathurst book on the Stevensons, especially to do with the weights, numbers of stones etc.

 

[LittleSister]

I had a book as a nipper, something like 'Great Engineers of the World', which included chapters on Eiffel, Stevenson, Smeaton, etc. I recall that one of them (Smeaton?) was responsible for building a breakwater (Plymouth?) and had specified it should have a face slope of, IIRC, 1 in 5, but this was overuled on cost grounds, and it was built as 1 in 3. It later failed and collapsed, settling at about 1 in 5!

 

[reeac]

If you think about big waves pounding high up on that breakwater then you can imagine the bending forces which would tend to open up horizontal joints in a conventional wall. In the case of the wall shown those bending forces will be resisted mainly by the long blocks themselves and furthermore the long slanting joints will be in shear rather than tension i.e. a much better situation for them. I can't tell from the pic. but maybe the direction of slope was chosen to take into account prevailing wind/wave direction - again to keep the joints in compression or shear.

 

[dylanwinter]

If you think about big waves pounding high up on that breakwater then you can imagine the bending forces which would tend to open up horizontal joints in a conventional wall. In the case of the wall shown those bending forces will be resisted mainly by the long blocks themselves and furthermore the long slanting joints will be in shear rather than tension i.e. a much better situation for them. I can't tell from the pic. but maybe the direction of slope was chosen to take into account prevailing wind/wave direction - again to keep the joints in compression or shear.

it is on the north coast of Forth

so it is south facing

the worst waves come from the East - the direction the camera was pointing

I was wondering if it was an experiment#

if it is cheaper than the "normal" way of laying blocks for harbour walls

D

 

[marklucas]

But also you can lay the lowest stones at low water and let the tide take you up as you build up each layer of the wall.