Monday, November 26, 2007

A Rising Wall

The hardest part was getting started, but a bit like a bag of potato chips once you get going, it is hard to stop. One more bucket full. One more big rock. Ok one more.

There was a major change in the plan for building this wall. I decided to dry stack the stones instead of setting them in mortar.

As fate would have it, I met a very nice stone mason at my new clients last week while I was working in the garden. We chatted for some time and I mentioned I was about to build a stone wall. He mentioned that he had written two books on the subject that I might find useful. When I said I would be mortaring the wall because it was a retaining wall he said a dry stacked wall was just as durable and might be better.

A few days later when I was back there planting 392 Tulip bulbs with an electric drill and bulb auger, my client loaned me his office copy of one of the stone mason's books, "The Art and Craft of Stonework."

Is the universe trying to tell me something? Like read the book before you build the wall.

So I did. It seems I can build a perfectly stable three and a half foot tall dry stacked retaining wall that is better drained, less expensive, easier to build and hopefully more attractive than a mortared wall.

Now in the book there were mostly fancy, very rectangular, straight edged, store bought stacking stones being used to build these walls. Well the rocks on site that I am using to build this wall could best be described as a rockpodge. They are a lot like the stones on Maui, very irregular, but a bit smoother. Also the stones here appear to be of several different types and colors. On Maui there was a more uniform type of lava rock in a given location.

So I am following the directions in the book. The landscape fabric is to keep the soil from moving into the wall and the gravel back fill with rain and freeze thaw cycles and then causing future freeze movement in the wall. The gravel helps fill the empty spaces in between my irregular rocks and adds more stability. I am also doing a double thickness dry stack as opposed to a single stack of stones. This should also give the wall more heft and stability.

I have stacked a fair amount of irregular stones in my time. Never to hold back a slope though. These were free standing objects and they have stood for a long time. Still I do have a certain trepidation about not using mortar. It just seems like cement is more permanent and less subject to movement. The wall will have a batter (lean into the slope) like it should and dry stack retaining walls have been done for a long time. It should be fine. If not, well than I'll do it over.

As the wall rises, the soil behind it will be moved and packed in behind it. Stack some stones. Fill with gravel. Lift fabric and fill with soil. Stack some stones. Fill with gravel. Shovel and pack some soil.

If only the stones were as light and airy as these Milkweed seeds, particularly the stones at the bottom of my grassy hillside. That's were most of the really big rocks went during the lot clearing and road building. I have big plans for them, closer to where they currently rest.


The County Clerk said...

Good plan. I especially enjoyed your description of DRESSED masonry as "fancy."

Do not underestimate the role of the gravel. If done correctly, it is the packed gravel that will hold most of the load. Angular gravel. It compacts and locks. This is why we gravel beneath roads and foundations. I'd go crazy with the gravel and use LOTS. The gravel will, to my thinking (if it is angular "base" gravel (or "gravel base")), become a self interlocked wall of substantial weight/mass/volume. Because it is gravel, water will not collect in it (or should not be allowed to) like water can do in sand and soil. No water, no freeze expansion, no thaw collapse. So, the gravel is key. Lock it down. Compact it.

Thing is, gravel is easily subject to mechanical weathering by wind, water runoff, animal burrows, etc. Mechanical weathering. So, you can't just build monumentally in gravel.

To my way of thinking the wall stones will protect the gravel from getting "unpacked."

The gravel will hold most of the load. The wall will hold the gravel. So yes, the wall is holding the load... but it is really holding the thing that is holding the load.

So... if you MORTAR the wall then you MUST MUST MUST allow for a GREAT DEAL of drainage THROUGH THE WALL. Even a small amount of trapped water will expand with enough force to dislodge things. A dry stacked wall (if carefully laid and interlocked) should be better for drainage.

You want water flowing through this thing. Out out!

That's my 2 cents.

Christopher C. NC said...

The book did say to be sure and get the gravel packed in there well. I'll try to be good about that. This wall will drain with ease and I will probably add a catchment and drainage system on the patio floor when when I get to that phase.

Now back to the wall. Brrr. It's cold out there today.

lisa said...

This is exciting! I think it looks awesome so far...the activity should keep you warmer, at least!

Queentileafa said... do have a way with words.

I was schlepping 4x4x8's and 2x4x12's and quikrete yesterday....between that and my new yoga regimen I can barely lift my arms to brush my teeth.

I admire your perseverance...

bev said...

I think a dry stacked wall sounds like a wonderful idea and will look more natural too! From what I have read these walls, if built correctly (which you no doubt will do with help of the book) will actually outlast mortar because they won't crack, etc.
I have only built a very tiny wall in my front yard but it is almost a Zen like experience fitting the stones. It will give you something to concentrate on besides freezing to death. (:

Pam said...

Wow - the wall looks great. I'm in the land devoid of rocks - on my (now frequent) trips to Virginia, I keep bringing a few rocks back with me. Maybe in about ten years, I'll have enough for a small wall. Yours really look beautiful, and I enjoyed the 'how' of it that you shared.

Annie in Austin said...

Thanks for the progress reports, Christopher.

This is so cool to read about and to see the wall in progress. The only thing I know about gravel is that the decomposed granite which is available here has sharp edges and it does pack together amazingly well for walkways and such.

Annie at the Transplantable Rose

Christopher C. NC said...

Schlepping? Queen Tileafa. I do believe that was the word you used way back when that exposed your mainland roots. Is there a new fence in your future?

I hope I build this wall right by following the directions. I'll be putting in tie stones (rocks that project past the wall into the hill) that help anchor the wall into the hill and the final cap stones are important to hold it all together. I just need 35 feet of 24 inch wide good capstones.

chuck b. said...

I own that book he loaned you and found it very inspiring... and I especially appreciated the section on "how to shop at a stone yard", me not being a contractor or landscape professional or anything.

speedyima said...

I'm originally from NC, and really enjoy your blog. Sounds like you're doing a great job with the wall. We build dry-laid walls almost exclusively, because they are so much better at resisting freeze-thaw here in New England, and yes, if you're doing a 4":1' batter on the back and 1" on the front, you should be in business, esp w/ the tie-backs. And I want to ditto the *angular* gravel statement -- none of the rounded stuff that would work so well for drywells, etc.