Are you planning on doing some concrete casts, but aren’t sure how to build forms? Or maybe you’re completely unaware of what forming is?
No matter which one it is here is a short introduction on building forms. These tips are good for small builds like if you need to fix a step or corner of a slab.
There are more detailed form instructions on this site on some of the posts like this DIY slab pour. It will suit you better if you need a small slab done.
Concrete forms in general
Concrete forms are the easiest way to get a durable, beautiful concrete object every time you want to create an object. If you’re looking to pour concrete for a big object for the first time, you’re going to need some help probably. After all, this is not a task most people are used to undertaking.
Of course, some people are more proficient than others, but even such professionals can benefit from the pair of helping hands now and then. Making things out of concrete gets heavier the bigger the project is. Starting from sink and countertop to patio and driveway, it gets more difficult.
But the get started, here are some tips for building forms to get your first projects underway.
Concrete Form Basics
Concrete formwork is the basics of all concrete work. Without forms, concrete would flow like water, making it impossible to make concrete conform to the desired shape and application. With these professional tips and advice for concrete form basics, you’ll be creating your own forms for your concrete projects.
It is put together just like a puzzle
Most often you start from doing the sides like with a concrete slab. If your project is something like a countertop or sink, it needs a bottom for the form as well. It’s as easy as starting to put those together.
When you are creating concrete forms for countertops, sinks, sidewalks, slabs, columns-whatever-keep in mind you need to remove the formwork after the concrete has hardened. If concrete is covering the form in any way, the nail work is buried or joints are compressed by concrete, your going to have the hardest time removing the formwork without damaging the concrete work.
Always plan ahead as you build forms. Think of it as a puzzle in reverse. As you add pieces to your formwork, make it easy to remove them later, don’t cover them with cement, and make inside corners easily come apart.
Keeping that in mind, always attach objects to the form from the outside. You don’t want to nail or screw anything so that it is inside the form where the concrete is. Taking that apart is unnecessary trouble.
Stronger is often better when in doubt
While trying to keep the formwork simple and easy to disassemble might be best for taking them apart, a happy medium must be found between strongly built forms and easily removable formwork. Wet concrete weighs much more than dry concrete and as it presses against the forms, you had better hope it holds!
Additional braces and stakes that can be removed as the concrete dries can help to keep concrete in its proper place; behind the form and not all over the ground. Attach diagonal braces at least every four feet per 8″ of concrete. Sidewalks can take a lot less punishment from the concrete weight, but footers and slabs will definitely need additional bracing.
Don’t go overboard when attaching parts
Just like a putt on the green, you don’t want to overdrive it. Using duplex or stacked head nails allows easy removal of form nails when the time comes. The dual-head allows the lower head to secure the nail shank tight while the upper head allows a claw hammer to grip and easily pull the nail free.
The same can be said with using screws. Don’t use more than you need to and if you screw something, make sure you can get the screw out.
I’ve seen it a few occasions that a screw has been left inside the form and it became a crowbar job. The concrete pour will be damaged like that.
Let the concrete cure long enough
Unless you need to get in there and finish the concrete, don’t remove the forms for 24 hours. This allows the concrete to shrink from the forms, creating a little space between the form and concrete.
Remove the stakes with a set of posthole diggers and pry out the form with a crow/flat bar. This kind of work will save you from some trouble if you try to remove forms too early and it hasn’t cured long enough.
What might happen is some crumbling on the corners etc. that would have to be fixed later.
Doing forms for concrete isn’t hard. It can start as simple as 1 piece of plywood to your outdoor step to pour a fix to the cracked edge or something like that.
The bigger and more complex we build, the more we have to plan ahead. This being just the basics, these tips should get you on the way to your first project just fine.
When you move into bigger projects, you will have to think more about can the form handle the weight and pressure and such. Concrete weight adds up really fast do even small slabs end up weighing a lot.
It’s still not a problem if done on the ground, but you can imagine if we pour something like a balcony. It will have to be supported from the steady ground level.
But these are just ideas for the future. I hope these small tips will get you started.