Just another brick in the wall...

[crfriend]

... with apologies to Pink Floyd.

I could just as easily entitled this one "Frost Heaves" as this is what actually caused the problem that I stupidly blew my back on the other day whilst fixing same.

A couple of years ago, Sapphire thought that some small retaining walls around the planting-beds below our higher terrace area would look nice -- and I agreed. It gave me a chance to teach myself a bit of "Masonry 101", and the results, to be honest, looked pretty darned good. Of course, then a couple of New England winters intervened and shoved the thing up into a peak where a smooth line once ran:

before.jpg

Well, the only way to deal with this was to disassemble the wall (which went underground about six inches), re-grade the substrate, and put everything else back together. Had I done this right the first time 'round I likely would not have had to do it again, but I'm actually not willing to bet on that.

So, out came all the dry-laid pavers to be laid out on the lawn in position so I know what goes where when it came time to put it all back together.

during.jpg

With the wall disassembled over the frost heave, it was then a matter of using a small trenching-shovel to shave down the irregularity and, over a sequence of trial and (mostly) error (Why does it always have to be that way?) get the substrate level again. Once things were nice and smooth, I laid the stones back into their places and got the end result:

after.jpg

Interestingly, this is what blew my back -- and it happened during disassembly. Moving a couple of cubic yards of mulch didn't hurt anywhere as much as picking up a 6-pound paver did.

I hate getting old. However, there is satisfaction in a nice-looking job, and I'm happy with this one. I just need to remember that the next time I have to do this I should use extra support for my frame rather than relying on my back alone.

To answer the question that the curious will likely have asked, yes, that is a gazing-ball atop a sink trap that we have in the flower-bed. The trap and drain-line got cut out of our kitchen plumbing several years ago when we had a sink replaced and one of us (I forget who) shoved one of the reflective spheres atop it to keep birds from drinking from it. It's lived in our garden(s) ever since. I rather like it.

[skirtingtoday]

(Structural Engineers hat on)
I don't know what the regulations/guidelines are in the US but in the UK, the underside of all foundations (houses/walls, column bases - everything) should be 450mm (18") below ground level. This is to get below the frost heave zone which affects the surface layers of soil in winter. This criterion applies even in fairly low walls such as yours.

The wall you have rebuilt seems to be set within this frost heave zone so I would expect further problems in the future particularly after prolonged cold spells when the warmer weather returns.

If I may suggest something else and that is that the bearing strata should not be topsoil. This has organic fragments within it and it will degrade causing it to settle into itself. Foundations should be taken at least below this and filled back up with stone generally 2-4" down in size with enough fines in it to get a good bearing foundation.
(Structural Engineers hat off)

Wall looks really good and you have done a great job with it - I just hope that the good work doesn't fall apart in the future.

(Structural Engineers hat back on)
Those stones look pretty heavy to shift about. In the UK there is a limit on how much a person can lift for Health & Safety reasons. This limit is 20kg (44lb). A concrete block 450mm long x140mm wide x 215mm high weighs almost 25kg (55lb). Such blocks are avoided unless it isn't possible. Any stone/block/item heavier than the limit needs a 2-man lift or special lifting equipment to work with it. May sound wimpish to some muscly builder bruisers, but that is the reason to prevent backs being pulled out.
(Structural Engineers hat back off again)

Sorry to hear about your back. Not a nice thing to happen and I hope that you do take it easier. As you say, we are all getting older and thinks we took for granted in years gone past, now become much more of a chore and a strain.

[crfriend]

I don't know what the regulations/guidelines are in the US but in the UK, the underside of all foundations (houses/walls, column bases - everything) should be 450mm (18") below ground level. This is to get below the frost heave zone which affects the surface layers of soil in winter. This criterion applies even in fairly low walls such as yours.

Had I the time, and extra cash on hand, to "do it right" I certainly would have dug farther down and used sand as a buffer between the soil and the blocks. I'm actually pleased that it lasted as long as it did without peaking. As far as getting below the freeze line here in New England goes, I know that the recommendation for things like water pipes is about four feet down to keep them from freezing in the winter. An 18" deep trench would have required some pretty heavy mechanical assistance; I did the wall using a shovel, a level, and in some places water.

Wall looks really good and you have done a great job with it - I just hope that the good work doesn't fall apart in the future.

Thanks. I do expect some problems with it, but it's an aesthetic element not a strcutural one, so I'm not all that worried about having to patch it every couple of years.

Those stones look pretty heavy to shift about. In the UK there is a limit on how much a person can lift for Health & Safety reasons. This limit is 20kg (44lb).

They don't seem all that heavy, but the only way to be sure is to get a scale, pluck a brick out of the wall, and weigh it. These are light enough that I can easily pick one up with one hand; I put my back out because I was being stupid and not minding my posture properly while working on the project.

Thanks, by the way, for the "Structural Engineer hat" tips. Good stuff.

[Kirbstone]

Nice pictures, Carl, and a comprehensive explanation of the problem & solution. Nice work. My thanks to ST for all the structural engineering comments, which have saved me a lot of typing.

Down on our 52nd parallel we go in for dry stone walls in gardens and boundaries a lot. These tend to waive the weight lifting regulations and consist of unmortared uncut natural stones selected from a pile and laid on a base usually well over 2 foot thick so the thing will support itself up to a max. of about 4 foot high. To prevent loss of stones the top layer only are frequently mortared.
Mind you, frosts down there aren't what you get in New England!

T.

[crfriend]

Nice pictures, Carl, and a comprehensive explanation of the problem & solution. Nice work.

Thanks!

Down on our 52nd parallel we go in for dry stone walls in gardens and boundaries a lot.

New England is rife with stone walls, mainly because New England is chock-full of rocks. It seems we grow them here; one can clear a garden of rocks one year and then have to do it all again the next as they've come up from below! So, it's not at all unusual to see two- to three- foot high stone walls traverssing the landscape here; in fact we have a three-plus footer that separates us from the golf-course. These are almost always unmortared, and usually marked the boundaries between fields, properties, and pastures. There is some heated debate about whether the use of stone for these walls was a deliberate one, a crafty use of handy material, or essentially "linear landfills" where the rocks that were gathered from the fields (back when we were still in subsistence-agriculture mode). I rather suspect the latter.

[Since1982]

You said: "I hate getting old".

Um, somehow, I don't think you're alone in that! WHAT, is a Frost Heave????? Us Floorididians don't know what "frost" is, much less frost heaves. Wait a minute. I do seem to remember back in 1980 when my Mom and I were looking all over the state for a place to move to, we visited the edge of Alabama and SAW some frost about a quarter inch thick. We ended up in Stuart Florida for 3 years before moving back to the keys. The "frost" WE saw looked like dirty ice cubes that had been walked on wayyy to much. I asked a walker what THAT WAS and were told it was "frost".

[henri]

Frost heave and volume change are problems that you find in climates where there are more extremes of temperature and the soil and sub-strata contains water. London's clay soils are a problem.
Clay retains water, so when very cold, the water freezes and it expands, and may 'heave up' a building where the foundations are inadequate. Volume change happens during a very dry season and the water drains away, redcing the volume of the clay.
Nothing to do with skirts or other related attire, but for your general edification.

Cheers R

[crfriend]

Frost heave and volume change are problems that you find in climates where there are more extremes of temperature and the soil and sub-strata contains water.

We have both problems in New England. This is particularly a problem for roads and highways where subsurface expansion causes damage to pavement which then fails when it gets warm again; this is the genesis of the chuckhole (or pothole, depending where one is from).

The chage in the horizontal line of my little wall is a beautiful example of the phenomenon. Water freezes as it expands, and this pushes anything around it aside; this is also the primary cause of rock erosion in higher latitudes -- water gets into cracks and crevices then freezes forcing the sides of the crevice apart. After enough freeze/thaw cycles the rock structure fails and the rock falls apart at the crack. This is what brought down New Hampshire's "Old Man of the Mountain" a few years ago. We have a rock in the same flowerbed that shows this brilliantly; I'll get pictures when I return home.

[r.m.anderson]

cr - - -
You crack me up in more ways than one !
Was one of those cracks what caused your back problem ?

Good thing kilts & skirts are not all they are cracked up to be !
Imagine coming apart at the seams due to frost.
The clothing police would have a tough time stitching Humpty Kilted Dumpty back in one piece.
At least this type of crack is preferred to another unmentionable one.

Enough-Enough-All Right-All Right !
I am done !

rma

[crfriend]

As threatened promised, here's a textbook case of what happens to stone in regions that repeatedly freeze and thaw. This example is one of the separators between our "upper terrace" in the rear flower-garden and the "lower"; the rock is about 24 inches tall, 36 inches wide, and maybe 14 inches deep at the widest. There's a six-inch ruler for scale on the closeup.

Oh, Mr. DeMille, I'm ready for my closeup:

cracking1.jpg

Here we have the top front surface of what's likely an 8 or 9 hundred pound rock. It was put where it was with mechanical and hydraulic assistance. I am nowhere near stupid enough to try moving it -- no matter what Archimedes had to say -- so it's been undisturbed in this spot for better than a decade, so what you're seeing is what Mother Nature (who has no pity, recall) has done to the poor thing. Multiple fractures are visible, and these are getting wider by the year; in fact, there is a single long crack that divides the entire thing and goes completely to the ground. If this was on the side of a hill and didn't have support it would have fallen by now.

Here's the front of the rock:

cracking2.jpg

This shows the long crack as well as some of the lichens (amazing things, those!) that have taken up residence on it and that we try very hard not to disturb; they're slow-growing. I do not know how deep that crack is, but based on what's visible on the top of the rock I rather suspect it goes all the way through.

We're not going to get an avalanche any time soon as everything is already in nice safe contact with the ground, but I rather suspect we'll start to see some organic growth taking up residence in the cracks in the next couple of years -- and that's the second biggest contributor to tearing down the mountains. It's not as spectacular as tri-nitro toluene, but it's just as certain; one only needs to be patient.

[sapphire]

cr... Remember the Old Man of the Mountain?

For those of you not familiar with the state of New Hampshire, there was a stone outcropping that resembled the profile of an old man. One day, the whole thing just came crashing down. Made everyone sad.

[skirted_in_SF]

A durable image of the Old Man of the Mountain is on the New Hampshire quarter ca 2000.