I like alternative and traditional building systems. You may not have gotten that impression from my enclosure topic. But it's true.

That said, I have been doing a lot of research on clay systems.

I am working on designing and hopefully soon building a traditionally built Swiss style frame for some extra shop space, and I want to use a traditional method to enclose the frame as well.

That said, right now I am looking at a system employing a clay infill covered with vertical boarding on the outside and lime plaster on the inside (or maybe boarding on the inside as well)

For the clay infill, I am considering pre-making the infill in the form of largish clay bricks which will already be dry by the time of raising (which right now the goal for raising is fall of 2011) and will be stacked between posts spaced at about 6 to 8 feet, with a brüstungsriegel (don't know exactly what to call this in English) spanning between the posts at the wall's midpoint, or perhaps two of them between every post for added support of both the infill and the siding.

I have a few questions about this, though.

1: How exactly should the clay slip be made? And what consistency should be used if I will be making bricks and not filling large cavities all at once.

2: What is a good way to cement the bricks together? Would just fresh clay do the job? Is there a preferred method? I don't want to just dry stack them, as this would leave gaps that could (and therefore would) create drafts

3: Would it be a good idea to coat the insides of the timbers with a thick slip so that the infill gets 'stuck' to the timbers a little more, or is this not worth the added effort since the expansion and contraction of the timbers will negate this anyway.

Efficiency isn't really too great a concern on this particular building. It will be heated with wood and at least initially not cooled at all (we'll see how long that lasts come summer time!)

However, the discussion of efficiency is certainly welcome. Part of the reason for using this system instead of strictly traditional infill of straw-clay or fired brick is to test the feasibility and performance, and to see how well it works in this climate, and also to see how it works labor wise.

A possible variation to this for efficiency purposes would be to have two layers of woodchip-clay brick with a cavity between them which is then filled with cellulose, a method I have heard of already so it is not my own I know. One layer of bricks could be set on the outside of the frame so that it covers the timbers, and have 2x4 nailers embedded in it somehow if siding is to be applied. I know of an old house that burned down a few years back that was structural brick, 12" thick solid brick walls, with a 2x4 framework added to the exterior so siding could be applied (it was an Amish house originally, that's why the brick was covered with siding)

DL, are you using 100% clay for the bricks? Or lighten them up with sand, straw or wood chips?

1: I have used a mixer on the end of a 1/2" drill, same as used in the drywall business for mixing compound in the 5 gallon buckets. On a small scale use 5 gallon buckets larger scale use garbage cans or an old bath tub. Raw clay, not dried and pounded to a power, it is nice if it can sit in a pile for a year for frost action to break it up a little. Place the clay in the tub and let it sit for a while, overnight if possible and go at it with the beater. Wipe it into a cake like batter or even a little more thinner like paint. For light clay and straw you should be able to stick your finger in the clay slip and just make out your finger print. You can always add more water or clay to gain the right mixture. Screen the slip before you use it, to filter out the unwanted grit, just pour the slip through the 1/4" screen into a fresh container.

2: Having no experience in clay brick and clay mortar, my guess would be a sand and clay mixed mortar. I would also be curious how a lime mortar would function?

One of the functions of lime mortar is it is the weak link with the older bricks the mortar will fail before the brick, for it is softer, allowing things to move a bit, then reheal. Where if you use a modern mortar which is harder in combination with the older brick the brick will fail which is not so good. If using lime as the mortar for you clay brick would the brick fail as they could be softer than the lime mortar? I take it that your brick will be unfired.

3: I have seen, at Fox Maple, where they used a rabbit cut into the face of the post to form a key for the clay infilled walls, in hopes to stop the draft. I would use such a technique to try to stop or slow the air movement at the post. I'm not sure of the size of the key, 1"x1" perhaps and maybe with a chain saw.

One of the draw backs to clay is it has to fit into a time line to allow the clay to dry before frost can harm the undry wall. Brick made in the spare time allow the wall to be built with a wider window. Probably not in mid winter.

I like this stuff too.

Tim

I've always thought clay / wood chip / hemp / whatever bricks would be a good use for melding 'alternative' methods into contemporary timelines. One could make the bricks on of offsite - maybe under a temporary greenhouse roof set up with cross draft fans or sealed with heat, let them cure, then stack and add to the frame. Would the bricks be easy to cut / trim to gables / eaves / door / window sizes?


If you are planning wood siding... why not frame up a 2x4 or 2x6 wall that is the module of your brick? Stack the bricks inside the stud bays... then somehow be sure you stuff any cracks, maybe a skim coat? Or a 2x2 framing inside that is filled with cellulose?

Sorry I should have clarified, my question about the slip was not how to mix it, but more about composition, such as do you just use clay and water, or would it be good to mix some kind of reinforcing or anti shrinking agent like sand or lime in as well? And about thickness.

And yes, the intent is to make the bricks with a mix of slip and woodchips, using as high a ratio of woodchips as I can manage to make the whole assembly both lighter and better insulating. As you may imagine, I produce lots and lots of woodchips! And furthermore, I don't throw anything away that I think may be useful. So I have lots of woodchips. The original intention was to build myself a furnace that could effectively use my waste products for heating, but I like the idea of using them for building better. Especially those chips produced by hand hewing timbers.

The German method when using a brick infill is to cut a v-groove in the posts, and give the bricks that butt up against the post a corresponding protrusion. This anchors them in and also stops a draft. A key would work if I were putting the mix in wet, so it could slop into it, but dry brick won't do that so well.

I did find that for adobe brick, the mortar used is the same mixture used for the bricks minus the straw.

I like the idea of using bricks because it means that I don't have to let the house sit around for 2 weeks while I wait for the clay to dry. I can stack the brick in, maybe wait 2 days if that for a skim coat to dry, and go right ahead with siding and finishing. IT also means I am much less dependent on the weather, and can fit this into a practical time schedule much better and so become much more effective and profitable. For this project it means I can raise my frame and stack the bricks during the fall or early winter or spring when work is slow and I have time to spend on personal projects

My thought with using the slip as mortar was that it would re-wet the outside edges of the bricks and maybe cause the assembly to somewhat melt together. Also I thought of a method of tying two rows together after I posted this that would make the infill more stable than if it were a single layer or 2 layers stacked next to each other, especially if the bricks are tied into the timber via a groove.

I am thinking right now that it may work to stack the bricks with a little sludge between rows and between layers, and against the timbers to seal the whole mass as much as possible, then plaster over the whole panel with some more sludge to fill any cracks, prior to whatever topping off method will be used.

Bmike, I am not quite sure what you are trying to describe in you post, could you please clarify for me?

The chips from the boring machine are very nice as well. I have a few garbage bags of them waiting for the right time. I sweep the floor clean and collect them after boring. I also place a box under the timber to catch them as I knock them off the top of the timber.

The slip should be thin as paint and just a coating is needed on the woodchips or straw and lightly placed into the brick form of slip form on the wall. Depending on the climate and conditions 2 weeks will not be enough time, thickness is the major factor, the thicker the wall the more time to dry like all summer. Bricks allow more surface area and quicker drying times, too, a real advantage. I should adopt this method.

I know that when August wraps up drying time increases. I can see a greater drying time with my sundried blueberries toward the end of the month. Twice as long as in the first half of the month. Days getting shorter, cooler, we are approaching my favorite time of the year.

It is said a green house will gain you a climate zone south this would add to the drying time of bricks, maybe a late summer project.

Tim

To me, shorter drying time is not the only advantage I see to making bricks. The biggest advantage I see is that it allows you to make the bricks well before they are needed. You can produce the infill at the same time you are cutting the frames, or even well beforehand. This means it doesn't matter if the bricks take a month to dry (in the case of wood chips, faster drying time is advisable for straw, because straw tends to rot easily) because I have several months before I even need to use them. The major disadvantage I see is that you need a large area to store them and dry them out.

I really like the idea of making my infill out of my waste from cutting the frame and hewing the timbers. Right now I have a great abundance of wood chips, and I will only be making more!

I have another question or two...

What are the different properties of gypsum plaster and lime plaster? I know lime is superior, but I don't fully understand why, and my inquisitive nature forces me to seek the answer...

Also, does anyone have any experience with clay roof tiles?
As part of the traditional system, I am considering covering my roof with rectangular clay tiles, and was wondering if any of you had any experience using a clay roof. At this point though, I am considering using regular asphalt shingles instead -because they are readily available and look reasonably similar to the rectangular tiles. I know they're not ideal but they will work.

Can't help with the gypsum question. One feature of lime is it has the ability to heal small cracks. I don't know if gypsum does this?

Autogenous Healing - When hairline cracks develop in the mortar, hydrated lime reacts with carbon dioxide in the atmosphere. This reaction produces limestone which helps to seal the crack and fill voids in the mortar. This explains the increased moisture resistance noted after six months of curing in two studies.

Ratios for mixing clay and even lime can vary depending on the clay content of the soil and the type of clay, moisture content of the added binder is also a factor, dry sand, wet sand, dry chips fresh chips. It is advised to do test samples with different known ratios to find the best sand to clay mix, ranging from 1:3 to the other end of the spectrum 3:1. As stated the ratio depends on the clay content of the soil used. So mix according the material at hand. To answer your first question, it will depend on the soil "you" have. My ratio will be different. Test blocks and more test block and it will be revealed.

I find one reason for the lack of use with natural materials is they are not a ready mix, like Betty Crocker cake mix. You have to fool with them, something todays society doesn't have the time for.

Home made cement roof tiles, no nailing required. Slate?

Tim

Hi,
regarding gypsum and lime, they are both calcium carbonate or calcium magnesium carbonate based products - so limestone, dolomite, seashell, bone, even eggshell. Gypsum, also known as plaster of Paris, is calcium carbonate in powder, so pulverized dolomite lets say, form, and was developed as a faster drying and simplified version of lime for stucco work and has really no mechanical or binding uses. When the calcium carbonate is processed in ovens to around 900 - 1200 degrees C, (The process goes further but I cannot really explain in English), carbonic acid is cooked out of it and it is converted into calcium monoxide. Water is added which converts it into calcium hydroxide. Calcium hydroxide is the white, or slightly off white when it comes from seashells, powder that you would buy at the shop as lime. Once it is used, the process begins to reverse itself as it takes up carbonic acid from the environment and reverts again to calcium carbonate. So after 100 years it will be harder than it was at 1 year or 50 years.
It is not only self-restoring, it is self regulating in that it takes up and releases water from the air, it is somewhat elastic as you would see if you ever walk through the streets in Amsterdam and it is a disinfectant - good for painting the stall and chicken coop - among other very fine qualities. The big disadvantage is that once it is processed it begins to revert and so cannot be kept indefinitely.

If you do use lime in your clay mixture that is fine but be aware that you cannot then reuse it, whereas without lime in there the clay can be re-used.

On your other point, I've got clay tiles on my barn, and have used them in other situations and depending on specifics they can be an ideal roofing material.

Thanks for the info about plaster!

I was wondering primarily for use as an interior finish of the walls panels. But it's good to know too for future reference.