Fabric Formed Posts




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Fabric forming is one of the easiest and cheapest ways to form concrete. Instead of time consuming and costly wooden or metal forms, you use little more than a plastic or similar fabric. The end result is not only aesthetically beautiful, it is also stronger, because it lends itself to rounded shapes, compacted pours, and consistent curing.

The basic principle is simple. Cut your fabric to the required size, attach it to something solid which is then braced to hold it in place, add reinforcement and pour the concrete into the flexible form.

Many shapes and uses can be created with this method, but we will focus on a simple column. You can use this system for standalone columns or posts, or for posts that attach to an existing wall. We will describe a standalone post, as this is a little more difficult.

For more detailed instructions, click here.
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Step 1: Base

It often helps to pour the base of the post a couple of days before pouring the rest of it. This way, the bottom is held in place while you set up the forms.
- Dig a hole, about 12 inches in diameter, where you wish your post to stand, whether it be at the base of an existing wall or on its own. The depth of the hole will depend on what type of force will be exerted on the post.
- Place metal reinforcement  in the hole, raised up on rocks or plastic (you want concrete under any metal, so that there is no chance it can leach water and rust).
- Level the metal (both east to west and north to south) and hold it in place with a couple of boards between it and the ground. [If the post is against a wall, attach the metal to the wall if possible, with a gap in between them.]
- Pour concrete into the hole to just above ground level. Make sure you tamp it down every once in a while to ensure that the concrete completely fills the hole. We use a 3:1 cement to sand/gravel mix.

Step 2: Form

The size of your form will depend on the size of your post. We will describe an 8 feet tall post, 8 inches in diameter. Adjust your dimensions according to your own needs.
- Cut a length of vinyl tarp, 8 feet long and 36 inches wide.
- Place two pieces of  8 feet 1x4s, 22 inches apart (the tarp will stretch a little, so make it a little skinnier than you want the post to end up).
- There should be about an extra 7” of tarp on both sides. Double this back on itself, to make it stronger.
- Staple one side of the tarp to one of the 1x4s, close to the inside edge. Put a staple every 2” or so – the concrete will exert quite a force on the tarp, so more is better than less.
- Staple the other side of the tarp to the other 1x4, checking the distance between the two boards (22” in this case) as you go.
- Remove the boards that were holding the metal reinforcement in place.
- Stand the form up and put it around the metal reinforcement of your post, so that the two 1x4s meet, flat against each other.
    [If your post is against a wall, just put each board against the wall on either side of the metal.]
- Screw the boards together at the top, bottom, and once or twice in the middle.
- Level the boards in two different plains, and then brace the form using lumber or metal.
- Pour concrete into the plastic, patting it as you go. You want the concrete a little soupy, so that it fills the form better. However, remember that the drier concrete is, the stronger it will turn out, so do not make it soupier than necessary. Patting helps to compact the concrete and release air bubbles that can make the post weaker. If you pat it too much, the post will start to bulge at that point.
- When the concrete is hard to the touch, take down the braces and then release the screws and carefully peel off the form, which you can store for reuse. We have found that concrete sets up far quicker in a plastic form – we don't really know why.

Step 3: Get Creative

There are all kinds of things you can do to a fabric form to make the end result more interesting. Any wrinkles or restrictions of the tarp will be transferred to the concrete. For example, if you weave string across the tarp when it is empty, the concrete will bulge out around the string, leaving a weaving pattern in it when you remove the form.



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    10 Discussions


    5 years ago on Introduction

    This would be a great use of old carpet. You could shear off the nap and mix it in with the concrete as fiber reinforcement, and then use the carpet substrate for the forms. It would present a texture which stucco or other plastering would probably adhere to as well. With regular straps or windings around it, you probably wouldn't need the wood strips at all.

    1 reply

    Reply 5 years ago on Introduction

    The carpet might be too much of an open weave, which would let water escape and cause the concrete to dry out.

    The nice thing about the plastic is that it is reusable and you really don't need any finishing, like stucco.

    All that being said, I do think carpet could be used.


    5 years ago on Introduction

    really love the fabric form idea. thanks for sharing.


    5 years ago on Step 3

    Wow, this looks very cool. What are good sources for latex bonding agent - materials, and or mixing ratios? Very good write up, I'm glad I was able to stumble upon it. Are there any standards which meet international bldg codes or locals, one could go by if happened upon an inspector or filing a permit? I know there are great possibilities.. I guess the hard part is proving it safe, so you can implement it. :/


    5 years ago

    I have used 30# felt for pier forms/ bases a number of times. Overlap the felt and pin it with a 16d or two. Likewise, level the top and attach to vertical stakes. Center it over a hole in the soil and make one pour with (stiff) fairly dry concrete. Tamp just a few times with scrap re-bar to eliminate voids. Strike off flush with level top. Post bases or nailer blocks can be inserted while concrete is wet or drilled in after cure. Felt is best used for fairly low level pours-- not tall columns as shown here.


    5 years ago on Introduction

    I'm fascinated by this! If I want to make a fabric table ... Do I drape fabric over a table and wet the fabric with concrete? I saw this http://www.concretefactorybda.com/project/fabric-flow-bench/
    And would like to try it. Any idea how its done?


    6 years ago on Introduction

    Brilliant idea and what looks like a beautiful place. Based or built as an earthship? I'll build my own some day!


    6 years ago on Introduction

    Great job! I've been idly wondering if this is possible for years. One question: how do you keep the rebar centered inside the concrete? I would worry there are spots where the rebar is barely covered or exposed.

    1 reply

    Reply 6 years ago on Introduction

    no, the rebar is easily centered by tying it to the support boards at the top. There are no spots where it is exposed. We pour a base first to anchor it, which holds the bottom.

    This technique can be used for lots of things, not just posts. You can make walls, footings, roofs, etc with fabric forms.