«The Cob Builders Handbook You Can Hand-Sculpt Your Own Home Table Of Contents: Acknowledgements and Warning INTRODUCTION What is cob? Why build ...»
gracefully shaped wood for hangers, hooks, curtain rods, decorations shelves • plastering stuff: swimming pool trowel, mortar trowel, smooth burnishing • stones, pretty colored clays, manure from grass eating animals, pigments, charcoal for black pigment.
hydrated builders' lime if you want to whitewash •
The object of the drainage system is to divert water away from your structure. You will be creating a dry island for your home to sit on. In some areas, a berm will be all you need to redirect water. In others, a French drain and/or a berm will redirect the water. There are more details about these drainage systems late in this chapter.
If you have the time, there are advantages to starting the drainage before building.
While you are making your house, you can observe how the drain is working and adjust it if necessary. Cover the ditch with plywood to prevent accidents. It will lessen the risk of flooding during construction. And when you are finished building, you will be able to sit down and relax sooner in your new home! If your weather and timing is such that you are unlikely to get flooded out while building, the drainage can be done after you've finished the house.
Test Holes The first part of the drainage job will be to get to know your land's natural drainage.
In the wet season, dig a few test holes where you imagine your house will be, as well as digging some holes uphill of it. Do the holes drain well or do they fill up with water? This will give you a good idea about what's going on under the ground and how much you'll have to do to divert water. A sandy, pebbly soil will let water filter through. A soil with high clay content will expand when wet and block water from percolating through it. (Make a little fence around the test holes or cover them with flat rocks or plywood to avoid twisted ankles.) Making Your Drainage You may want to use earth-moving equipment, if you have a big job or if there's equipment there anyway for the road building. If you do get machines in to do work, watch them very carefully! Their drivers probably do not have the same familiarity or respect for the land that you do, and can do a lot of damage in a short time. Digging by hand is usually more accurate and less destructive to the land.
Mark where your foundation will be with straw bales, stones, or wooden stakes.
Step back and look at the site from a distance. Imagine where the underground water and surface water will flow.
On a sloped site, create a drain and/or berm starting uphill and flowing around the house. (See illustrations next page.) Your drainage system will direct water to the sides and downhill of your home.
Consider how you can make use of the water you divert from your homesite (a pond, garden,trees etc). At least make sure it isn't causing erosion. If you won't be catching the water from the roof gutters for drinking or gardens, you might want to channel it into the drainage system too.
Creating drainage on a flat site
Avoid building on level sites if possible. They are better for gardening and much more challenging to keep dry. Obviously there has to be somewhere for the water to go, so if you must build on the flat, you'll have to create a place for water to flow to. Make a ditch all the way around the house, draining into a big hole filled with round river stones and/or pumice. This will hold the water and let it soak slowly into the surrounding ground, away from your house or into your water-loving garden planted on top of the drainage area.
In Eastern Nigeria, people solved the problem of building on low, flat, wet land by piling dirt into raised platforms and making their cob homes on top of these, out of the wet. If you do this, remember to tamp the dirt often as you build up the platform.
Berms To divert surface runoff, shovel dirt into a narrow, long, hill-shaped form as shown.
You've just made a berm. Make sure the edges extend far enough beyond your structure, so that the water leaving the berm and flowing freely down the hill will miss your building. You might want to direct the water from your berm to nourish your garden or orchard. If you decide to make a drain and a berm, put the berm uphill of 23 24 Your test holes will also give you an indication as to how the water flows under the surface. Ideally, the bottom of the drain will be lower than the bottom of the foundation. (See illustration page 55.) The deeper the drain, the safer you are, and the more gravel you will need to fill it. If your drainage ditch is quite a way uphill from your home on a steep slope, it's impractical to make the ditch deeper than the foundation. You'll have to use your judgment about how deep to go to catch any water that might otherwise end up at the house. You might get away with simply making it deeper than the foundation in relation to the surface of the ground.
Slope of the ground
For proper drainage, you will need to slope the ground level away from your home in every direction. To achieve this, dig on the uphill side of your homesite until you've created a slight downhill angle from the house, then dig your drain at the bottom of that slope. You will be doing three things at once: creating drainage, making a place for a walkway or patio, and getting dirt for building. While you're digging, put the dirt somewhere handy for later use. (Hint: Inside the building is a convenient place to mix cob. Leave enough room to maneuver a wheelbarrow.)
25How far is the drain from the foundation?
The drain can be right under the foundation, or it can be anywhere from 1-10 feet or more away. If you want to leave the drain open while you're cobbing, it'll be more convenient if it's far enough from your house to be out of the way while you are building. Make sure the water will flow from the house to the drain!
How wide do I make the drainage ditch? It needs to be wide enough to fit a 4 inch perforated pipe and 2 or 3 inches of gravel on either side of the pipe. You will need enough room to get your arms in to lay the pipe. (See tips on page 31.) Completing the drain You can either do this step before you start the house, or wait until you're sure the drain will function like you want it to, after a series of heavy rains. If your soil has a lot of clay, sliding a shovel along the sides of the ditch will make the clay smooth and slick. This can harden and create a water resistant barrier that blocks the water from entering the drain. Try to avoid this by roughing the sides to allow water in.
Lay 2 inches or more of 1-2 inch diameter round river gravel in the ditch. (Crushed gravel takes a lot more energy, big machines and gas to make, and its flat sides sit closer together, leaving less space for the water to flow in, but if that's all you can get, it'll do.) Next, lay the perforated 4 inch plastic pipe on top of the gravel. If you don't like plastic, you can go the old fashioned way and use cylinders of ceramic tile laid end-to-end. You will be creating an empty space for the water to flow along after it runs in through the perforations or between the tiles.
Tips for laying the pipe so water flows all the way
Start at the high point in the ditch and run the pipe or tiles at a slight slant to where you want the water to go. Here's a trick to make sure the pipe or tiles will drain the way you want them to. (You'll need at least a 1/4 inch drop for every 10 foot length.) Starting at the high point, lay a long, reasonably straight 2x4 on top of the pipe or
When you have the pipe or tiles where you want them, fill the ditch almost to the top with round clean gravel. Fill it the rest of the way with 3 inches of straw and/or a 1/8 inch stack of newspapers to help filter out the dirt particles that might clog the spaces between the pieces of gravel, or block the holes in the pipe. (See illustration on page 55.) Pathways or garden walls can be built right on top of the drains or cover the drain with topsoil and plants. Do not cover it with a clay soil because the water will have a hard time getting through it and into the drain.
Once the foundation is made it will establish your options for all aspects of the building. Read this book carefully before you start on your foundation.
Libraries and other organizations in the natural building network have lots of information on how to build various types of foundations. Before deciding what kind of foundation to make, assess your options, materials, resources, and the time that you have available.
Give yourself lots of time for the foundation work!
You'll end up with a stronger foundation, and have much more fun making it, if you feel you have plenty of time to work on it.
The soil is most likely to slip where it's been disturbed:
- where the bank has been cut,
- where soil has been added to make a level surface (see arrows).
If you're building on a steep hillside, instead of taking one big bite out of the hill,
You may decide to build up the floor on the downhill side of the house site.
If you dare, and if the hill is not super wet, the retaining wall can second as a foundation. If you decide to do this, it will require lots of care to keep the water out of the house!
If you do, it's still a good idea to put the foundation on solid subsoil. If the hill is steep and you are adding a lot of in-fill to level the floor, build a heavy duty foundation that's tall enough to support the floor in-fill. You might need to build a retaining wall on the uphill side of the house. This will ensure that the hill stays where it is, after you've taken away the supporting soil when you've levelled for the house site.
Designing the door area It is vital that you read the following chapter on floors (starting page 57) to help you design your foundation and threshold.
The positioning of the door(s) must be decided when you are designing your foundation. Underneath the door, the height of the foundation must be lower than the height of the rest of the foundation. The depth of the foundation under the door may need to be increased so that there will be enough material to make sure the foundation is continuous. If you live where the ground is stable, you may opt to have no foundation under the doors or a much less substantial foundation under the doors and under any sunny, glass-filled, lightweight walls.
Decide what material you will use for the top surface of the threshold, and build it accordingly. If you are using the foundation stone itself, make sure it is as flat as possible so the bottom of the door seals well.
Make sure that the threshold will be a dry place.
Slant the outdoors ground away from the threshold.
• Plan to extend the roof eaves or add a porch to protect this area from rain.
• In temperate climates, place the door somewhere other than into the • prevailing wind, or on the cold side of the house. In hot climates you may want to put it on the windy side of your house.
Raise the wooden door frame above ground level to prevent rot.
• Where the ground level is a lot lower than the floor level, you may decide to • make outdoor steps or a ramp up to the door. (During building you'll want a ramp for dragging tarps of cob and for wheelbarrows.)
Setting up the door frame Get your door and framing material. If you are not a carpenter, this is a great time to invite a carpenter friend over to give you a hand. When you've built the foundation to the bottom of the door opening, set up the door frame, attach it to the foundation, level it, and brace it well. Putting the door frame up as you build the foundation and before you start cobbing saves you future headaches. You'll be assured that the frame for the door will fit well against the foundation and the cob. Carefully build the foundation to the frame. You can fill in any gaps between the frame and the foundation with cob later. Add the keying system to the frame so that it will be attached to the cob as you build. (See page 111 for details about keying systems.) If you are doing a poured foundation, bury bolts into the concrete to attach the door frame to.
Planning for a future addition If you want to add another room in the future, extend the foundation for the addition while you are building the present foundation. (You don't have to build it all, just the first 1-2 feet.) This will ensure a strong connection between the two stages of the foundation.
Make a second threshold and door frame leading into the future addition.
If you haven't found a door yet, make the opening to fit a common sized door. Leave the door open for easier access while building. Then insulate and board up the opening, or have two future addition outside doors until you add on. (See page 100 for more on future additions.) Other things to think about Where the wall makes a sharp curve, it is naturally strong. The wall and the • foundation at a curve can be slightly thinner (to save material and labor) than under the straighter parts of the wall.
If you plan on a very heavy roof, like ceramic or concrete tiles, add an extra • inch or two of width in the supporting walls for good luck.
The foundation under interior walls can be less substantial than for the outside • walls, because there will be no need for protection from moisture or frost.
Unless the interior walls will have the job of supporting the loft or roof weight, they can be thinner (8 to 10 inches at the base, at least 5 inches at the top.) Again, remember you can curve these walls for strength.
Any buttresses you're planning will need foundations under them. (See design • section, page 13 for more information about buttresses.) Built-in furniture that will be against the wall can have its foundations built into the main foundation at the same time, and can serve as little buttresses. Because built-in furniture will be supporting much less weight than a wall, it will need a less substantial foundation.