Ever wonder how they made those odd shaped concrete buildings or curves or triangle shapes? It is not a secret and your imagination is about the only limiting factor. Money of course helps for purchasing materials but in many cases used lumber or plywood will do just fine. Be inventive. A cardboard tube from the inside of a carpet roll when cut in half, makes a great sluice or slide form for a fountain or stream. The wood reels left over from an electric cable roll make a great inside form for a circle for a doughnut shaped form. All these things are free for the asking. There are also specialty materials available such as a product called “wiggle board” which can be flexed to achieve nice smooth curves to the faces of the finished concrete. Take a walk through your local big box store with the thought of finding things that can be used to form concrete. You will be amazed at what you find. Empty pails laid sideways in a wall form make perfect port holes or round window openings. Square, round, triangular or just about any shape you can imagine can be found. You can always make your own shapes as well. Lets take a look at how to form a curved wall.
Starting out with a plate on the floor to create the wall shape you want is your first step. You cannot bend a two by four of course so you use a larger piece of lumber and cut the shape (or part of it) from that. If the curve fits on a two by six, lay out the curve and cut it out with a saber saw. If the curve is longer than your board or more than what can fit on a two by six, use a two by eight and so on. Once all the floor pieces are cut, make a duplicate set which will be the top plate of your form work. Lay the pieces out in place and fasten them to footing or floor. The curved wall is now much easier to build. Using standard two by four lumber, place them as close together as possible along the floor plate to create a curved wall. Install your top plate. Using one quarter inch thick Luann plywood, and starting at one end of your form affix the plywood to the studs and then gently bend the plywood around the wall. You may want to coat the plywood with form oil prior to installing it and although this makes the installation a bit messy, it softens the plywood and makes it even easier to bend. Fasten the plywood to every two by four. This adds strength to your form work and keeps the plywood in place as it dries out. Once the face form is complete you can complete the backside of the form and pour your concrete. Odd shapes may be built into the face of the form to provide recess’s in the concrete or holes in the wall and so on.
Free form concrete can be great fun but requires a concrete pump that can shoot a concrete product called gunite or shotcrete. Any shape is possible and is limited only by the pull of gravity. Rebar, foam forms and other items can be used as temporary forms for the concrete until it hardens. In-ground swimming pools are quite often made of gunite which is how they get those great curved wall sections and shapes. It takes a crew to use a gunite pump but once the basics are learned with enough helpers you can use one as well.
Concrete when suspended in air needs some type of reinforcing to help support the weight of the concrete. If you are attempting to do suspended stairs for example, get an engineer to design the rebar layouts for you. Concrete is very heavy and can cause serous injury or worse if a collapse occurs.
Try forming some small architectural elements in your garden and pour them using a bagged redi-mix. Steps, small walls, a pool or pond and then move on to the larger features. You will be amazed at how easy it is to make these great looking features.
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