Channel Blocks Up

This photo is just before we broke for lunch. Will and Ben are cleaning up the mortar mixer. Here you can see the channel block all in place except the last block which must be cut to fit (see below), the vertical rebar reaching up towards the sky and if you look closely, or click on the photo to get the big picture, you’ll be able to see the partition block laid in rough approximation of the rooms. Everyone had a lot of fun walking around the tiny cottage this morning, visiting the various rooms and talking about what will be where. Seeing the position of the walls brought up a lot of ideas.

One bag of Portland cement weighs 94 lbs. Mixed (2.5 half gallon scoops = about 15 lbs) with sand (5 shovel fulls – real precise – about 3.5 gallons), water (0.6 gal), PVA fiber (a handful), accelerant (~2 oz) and soap (dash) it makes about 4 gallons of concrete. No, those numbers don’t add up. I’ll leave it to you, the reader, to figure out why. Consider it a mystery question, leave your answer in the comments and we’ll discuss this in a future class. :)

The soap makes the concrete more fluid without adding additional water – thus it flows better into the cores and has a higher slump. In fact, it is almost self leveling. Cut the water a little to about 0.45 gallons, drop the dish soap, add lime and it ends up a nice stiff mortar mix.

With just one mortar mixer Ben or Will produces a 4 gallon batch in a five gallon pail about every 7 minutes. One person could probably keep two mortar mixers going at full production doubling production. The mixer person can do that all day long without wearing out. Using the kick the bucket method as we did last year on a pig hut is a lot slower and more tiring. If you need more than that and you would want to consider bigger equipment or a ready-mix delivery by truck like we did for the slab.

That 4 gallons of concrete fills about two cores in a three block high wall (thus six cores plus stretcher end gaps) if you add a few small rocks to the mix after you plunge the mix. Our technique is pour the concrete into the cores (hold the bucket a bit high so the stream folds), plunge it with a stick to force concrete in all the seams and joints, add rocks to raise the level as desired, plunger a little more and add metal (rebar, steel) if desired. Theoretically the fiber is replacing the need for steel but I like both, just to be sure. Over kill is an amateur’s best friend.

After I’m done I clean up the edges where any concrete has protruded. This made me feel more confident with the dry stacking since it is now all bonded together and there is the vertical pillar of concrete and rebar inside the cores. Effectively the blocks are acting as forms. Later I’ll parge and plaster the surfaces. Alternatively I have read about not filling and just parging the surface with a fiber cement. By filling the cores I’m also increasing the thermal mass of the house – a good thing.

I’ve experimented with cutting blocks down in a number of ways. Hammer and chisel works great for splitting end blocks to half blocks as well as several other splits. It is relatively safe, low on dust and quick. Hammer drill with a chisel point works too – it’s noisy and even faster – easier to make mistakes. A diamond blade on a skill-saw as I’m using here is the fastest way for taking a little off the top, and the most dangerous and dusty method. I could barely see through the dust and fogging of my safety glasses. Even with water the dust is a problem. But it does the trick quite neatly. In this case I was shortening a channel block by half an inch – bad planning.

A little experiment. I wanted to be able to pour cement down a set of cores but not have it go below a certain block to leave an open core below for utilities. I placed blocks on top of some pink-board, poured a little high slump concrete into the cores and let it harden. Simple and effective.

Here my youngest assistant takes a break from the hard labors of toting and hauling cement blocks. Breaks and reasonable work limits are key to being able to keep going on the job. We pace ourselves, stop for tea and an apple, stop at noon for lunch, break work at about 3:30 pm this time of year to start cleanup – if we wait any longer it gets dark and hard to see what you’re doing. That’s when mistakes happen – best avoided. You might suggest setting up lights to work into the evening but that would just mean we’d be wasted the next day. It is better to just keep up the pace day by day rather than wracking our bodies. Then with the occasional rainy day like yesterday we get a day off as well.

By the end of the day we had all the channel block mortared, rebar in place both vertically and horizontally and the front wall of channel block filled and level with the vertical poured wall of foundation along the front. Why you might ask did I do forms half way across and block half way across??? To experiment. I wanted to experience joining the two together. What better place than on a tiny cottage.

Did I get it right? Well, not entirely…

I forgot to leave a piece of protruding horizontal rebar from the poured vertical wall to join with the channel block of the masonry wall. I fixed that with a hammer drill and epoxy. I did not make this mistake again. Lesson learned.

I calculated my vertical wall based on mortar joints and then did dry-stacking for three joints. Oops. We fixed that as shown in the photo above by using wire to tie some pink board on either side of the masonry wall thus creating a form. Then I poured cement in there to raise it up to the height of the poured wall next to it and floated off the top. That worked slickly. A mistakge but I got to work with both dry stacking, mortared joints and a leveling top pour. As a result of this error I made a new technique for quick forms in the process and probably won’t make that mistake again. The new technique may come in handy for something later.

I also forgot to put in two anchor bolts. Oh, well. Something the hammer drill will fix later.

Other than those errors it went well. Now we’ll have a perfectly flat and perfectly level surface a
ll around for the upper walls.

Next come window spaces. The number of blocks per course will drop dramatically since most of the upper wall is windows so we’ll go much faster. Being more experienced will help too. On the flip side, we’ll be working higher up. See those tall pieces of rebar, I must lift each block up over them and set it down. Who needs a gym!

Every job site needs a security guard!

58째F/48째F Mostly Sunny

About Walter Jeffries

Tinker, Tailor...
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9 Responses to Channel Blocks Up

  1. PV says:

    Walter!!!! Whenm I gonna see yor best selling book BUILD YOR OWN HOME IN 30 DAYS!???????

  2. jessie says:

    There is nothing like practical work experience as a teacher, for you and your kids. Very impressive.

    (My husband is a builder who has little patience for many architects. Sometimes they seem to have had M.C. Escher as a college professor and can’t understand that just because you can draw something doesn’t mean you can build it. It takes actual building experience to help them overcome that.)

  3. bruce says:

    I’m a bit of an iconoclast. Why masonry block and not wood frame? the existing wood frame house has lasted for 200 years — and it’s much easier and faster to frame and get weathertight. A 20×20 building built on a slab as you’ve done with your block walls would be up in 2-3 days, and in keeping with your ethos of staying local, the wood could have come from your woodlands.
    I haven’t seen mention of building permits or inspections — if it’s not being inspected, you don’t need to have graded lumber. So local stuff would do just fine.

    I’ve done both masonry and wood framed buildings. The last masonry I had to have inspections every 4 vertical feet, save test cores from each load of concrete poured (for compression tests) and use a vibrator & 12″ slump. I’m omitting the rebar & I-beams required over window and door openings.

    Contrast that to my wood frame — frame the entire building and then go for a framing inspection, sheath it, sheathing inspection (for nail patterns and so on) and then cover with siding.

  4. Wood works and as you say I have my own. I’ve built with wood many times. It isn’t quite as simple as having it growing as trees though. One must select, cut, skid, mill, dry, etc the wood.

    This house will be earth sheltered in the end and wood is not appropriate. The concrete block is the first layer. On the interior there will be stone and plaster and on the exterior there will be insulation and stone.

    The house is designed to use virtually no additional input of energy beyond passive solar to keep it comfortable. A small wood cook stove, using a cord or less of wood from our land which we can grow and harvest, will provide more than enough heat to keep even Holly warm through the coldest, darkest Vermont winter. In the long term that will save energy.

    That saves money, saves energy, cuts pollution and in the long term is a better choice. Even the best built wood framed house won’t match that in part because the thermal mass of the house is a key component of the system as a whole.

    Stone is something that I also have plenty of. I would have liked to build the walls with just stone, no concrete block core. That was my original plan but I realized that I would not get it done if I did that. Doing just stone also would make it harder to use steel and fiber reinforcing. We don’t get many earthquakes but it just takes one.

    Lastly, wood does rot as demonstrated in the many houses I have worked on fixing. Even in the best of conditions wood decays. Wooden structures, and most conventional design, require a lot of maintenance. I want to build a house that requires little to no maintenance and will last a thousand years. Ambitious. :)

  5. homemakerang says:

    Holly is such a trooper too in all of this! You definately have a gem :)

  6. Aye, that she is! Holly’s the best, no offense to other models but I got a very good deal and wouldn’t do a wife swap! I thank her every day!

  7. Cheryl says:

    Am I the only one that can’t see all the pics? I can only see the first and last one. :(

    Earth sheltered, that will be cozy when it’s done, Walter! My sister in KY has one, and she really loves it.


  8. Anonymous says:

    Walter and Holly,

    I have found you site from the NONAIS website and have been reading your posts over the past months and I thought I would chime in on your new house.

    Why do you not want to restore your c. 1777 home??? I know you state that homes built of wood are prone to decay but solve the “water” problem and keep the house dry and you can resolve most of your wood related issues. I know because we just recently moved from a wonderful c. 1820 1200 sqf house in the Blue Ridge mountains of Virginia to our dream c. 1800 farm on the coast of Maine. Our current house boasts 2500 sqf of living space with another 500 sqf potential. England has many oak timbered houses still standing from the 14th to 16th centuries.

    We have quit the rat race of Northern Virginia and now raise poultry and Icelandic sheep on a Salatin model of pasture rotation with 20 good coastal Maine acres. 10 have been somewhat cleared but the other 10 are now being harvested for timber for our c. 1800 barn restoration. Hopefully, these acres will be good pastures soon. A local man is helping us. He has a skidder, limber and trucks our wood to either the mill or the market – we are paying no costs (actually we are getting paid a small amount out of the total stumpage) and our lumber is going back into our farm projects. No “Canadian Lumber” here. It has really been no big deal and the lumber quality has been exceptional.

    We thought that we would try the “minimalist” route with our last home six years ago. After two years we found it was really not practical. We realized we would have to add on to our Virginia home to resolve our “space” issues. I cook alot and most of our friends and family converge on our house during the holidays. The kitchen had to be big and ours was actually the size of your house!!!!! I cook very much according to the Weston Price model and to do so – I need a great deal of space to move around (and at 100 pounds by no means am I big!!!). We also needed space for family and friends who would frequently visit.

    Block homes although very rugged tend to be damp and musty (I know from experience – my best childhood friend lived in one and I could not stand the smell of her house!!!). A good air circulation is wonderful for health (most people call these small drafts). I would think two very good efficient wood stoves in your early 1777 home and good caulking/glazing/sealing of windows and cracks would give you a beneficial air exchange and good heat retention – you would be looking for a balance.

    I hope you don’t take this the wrong way Walter, but as we have found – early homes are jems that should be candidates for restoration. Our c. 1800 cape is the perfect home for us – nice space, good light (in northern Maine this is important), well built to sustain over 100 mph wind gusts (actually we have had winds close to this but since our house is built like a ship – we never hear them), Unaltered floor plan, important architectural details, and a good foundation.

    I would be interested in hearing more about why your early home is just not good enough (besides being so drafty???).

  9. Anonymous,

    Some people like to restore old houses. I don’t have that desire. I would spend more money restoring our antique house than I would ever spend building a house of my own design. The continuing maintenance on the antique house will also be far higher than it will be for a house of my design.

    I won’t argue with the desire to restore old houses. They are beautiful. One of my brothers and my parents have both restored old houses. I’ve done it. But I want to build something better.

    So, the old house will be available for someone like you who truly appreciates it. Come and get it! :) The only catch is it must be moved to a new location. I want that spot for a hay barn or something else. If you really are interested go see the house’s web site.



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