Without sounding like a broken record–or iPod–we have a lot of board formed concrete in our project. If you’re new to reading this blog and want a description of what I’m talking about, you might check out this post.
I haven’t asked quite so bluntly, but reading body language I think the concrete team has more than a little bit of project fatigue, and are ready for the next big pour. To be clear, building board form walls is seriously labor intensive. And we have a lot of walls. Hence a lot of labor.
From early in the design phase knew we wanted board formed walls in our project. Finding out more about the process, and identifying a good contractor though, was more difficult than I expected. Googling “board formed concrete” didn’t help too much. Mostly I found a lot of examples of very expensive residential or commercial projects, with little information about how to do it or what it costs.
Locally, I talked to a few contractors who all said some version of, “man, I don’t know. You’ll probably need to find some old guy to do that for you.” (Board forming is a pretty dated technique.)
The helpful peeps at Olson Collins made a suggestion of someone to speak with. Olson has incorporated board form work into some of their projects, and in fact one of their contractors has built a pretty slick system for building formwork. Check out the pic below. The problem is, we couldn’t get any specifics from him beyond, “that looks really expensive, like maybe a hundred grand or something. I’m not sure though.”
Along the helpfulness spectrum, that suggestion was pretty far to the left.
So, this is all a long build up to walk through how Mikel and his team created our walls.
Our contractor, Carrie, has some experience with board form work, and what we’re doing is similar to how she created walls in her own house.
We start with forming walls like you would for normal, smooth-walled concrete using plywood and snap-ties.
Once the first side of the wall is up though, Mikel nails rough-sawn cedar to the inside. A lot of people use fir 2 x 4s, or 2 x 6s–wood that’s typically used for framing. This gets expensive though, and the fir tends to flake off and get stuck in the concrete. It also doesn’t leave as much of an imprint in the concrete as cedar–a quality we want.
Then Mikel needs to figure out how to work around the snap-ties. These are used to keep the plywood forms stable during the pour. If you’re not familiar with concrete, as it’s poured and set, it exerts a tremendous amount of pressure on the form work. The ties hold things together.
However, the snap ties can get in the way of the cedar boards. The way we worked around this is to use a variety of board heights. You’ll see this in our wall. We may have an 8″ piece of cedar, then a 4″, then a 6″, 2″, etc. I love the variety. Very cool.
The other thing we did was use a variety of thickness of cedar. Again, this will get picked up when the concrete is poured, and I think what we’ll end up with is a wall that looks a bit like an old ruin.
I found the cedar for this project on craigslist for a great price–59 cents per lineal foot. This is the upside of the end of the building season and a down economy, I guess. The material was all 1″ x 8″, and 7/8″ thick. So we sent it to a big shop and had it ripped in half. This effectively doubled the amount of wood we bought and now have some material that’s 7/8″, some that’s 1/4″ and some that’s about 1/2″. Mikel is mixing these in randomly.
According to Mikel, the most challenging part of our walls (beyond the sheer size) is the corners. When he gets to these, things get tight and it’s hard to maneuver the cedar, the rebar and the snap-ties. Mikel is also working hard to try to get the courses of wood to align–a nice touch for sure. He and Carrie also decided to add triangular shaped trim called chamfer strips that ease the corners. I think he was worried about our daughter getting hurt on a sharp concrete corner. Thoughtful, eh? (I also think it looks quite beautiful.)
The big pour happens early next week. The boys have about 30 feet more of wall to construct, then want to take a day or so to get the bracing right (remember the big pressure from the concrete?) and to get the walls perfectly straight.
Unfortunately I’ll be out of town when the forms get pulled off the new concrete, but I’m sure I can convince someone to take a few pictures. As Jennifer Love Hewitt might say, “can’t hardly wait.”
[…] links: Blog: Spokane Meadow House Blog: L+U: Concrete Video: Concrete Wall Form […]
What is the different of FORMED CONCRETE or Cast in Place concrete? because Cast in place concrete is also need form.
Well, I’m not a concrete contractor so might get over my skis here. But…yes, cast in place concrete requires a form. Otherwise you’d end up with a giant blob of concrete that would look like a giant petrified ant hill. So our walls were indeed cast in place, something essential considering it required 6 or 8 trucks and well over 200 yards of concrete. What made our project somewhat unique is that our walls were BOARD formed–meaning we used cedar boards instead of smooth plywood, which lends a pretty distinct look and texture. I wonder if you’re thinking of the different between Cast in Place and Pre Cast concrete. Pre Cast is typically a piece of concrete that’s formed in a factory setting. For example, a concrete fire pit, highway barriers, concrete railroad ties, etc. Hope this helps!
Every concrete is gernerally formed concrete. Cast-In Place simply mean that forms are erected on the site where they will remain so the concrete is casted in-place of its final location. Other than pre-cast concrete which is made off site for example in a factory and then shipped to site to be assembled. This is often used where the architecture and structure allow it to be more time efficient and less weather dependent that cast-in place concrete. But 99% of all concrete applications are formed concrete. I hope this helps. I am a concrete contractor in Edmonton/ Canada. I came here 6 years ago from Germany.
What is your average p/sf or p/lf?
I have done the same type of pours in the past using conventional concrete forms lined with wood. I would not use cedar now as it is too valuable a wood to be used as a throw away material. Rough sawn pine will give the same imprint and is grown as a forest product.
I agree. Simply use a good form release agent on your rough cut pine
supplements to get ripped and build muscle
How to form board form concrete. | Meadow House
We are trying to do a board form wall and have been experimenting with mock ups to get the desired look. The issue we are having is when we pull the forms we have air bubbles that have left thousands of small holes in the grain which looks horrible. We use a good form release agent and have experimented with various levels of vibration to remove these with no luck. Has anyone experienced this issue or found a way to avoid this?
Hi Bryan. Sorry for the delay. I’ve gone a bit dark with this blog! I’m not sure what to suggest given that my experience is limited to our own project. The thing that stands out though is to ask what kind of wood you’re using. Certain woods–pines like ponderosa or fir for example–tend to show less grain. Cedar on the other hand (what we used) does a good job of transferring its grain. And while we have a few air bubbles, they’re pretty limited. Hope this helps!
Any final pictures of the walls/house complete?
Hi espiritiv… I’m super far behind on posting. The best I have right now though is what’s on the home page, a few posts down. So…the three photography entries. Send me a note if you’re looking for something more specific. Always happy to share!
Greetings! This is my first visit to your blog!
We are a collection of volunteers and starting a new initiative
in a community in the same niche. Your blog provided us beneficial information to work
on. You have done a wonderful job!
Generally I don’t learn post on blogs, but I would like to say that this write-up very
pressured me to try and do so! Your writing style has been surprised me.
Thank you, quite nice post.
Hey fantastic blog! Does running a blog such as this require
a great deal of work? I have virtually no expertise in coding but I was hoping to
start my own blog soon. Anyhow, should you have any suggestions
or tips for new blog owners please share. I know this is
off subject however I just needed to ask. Kudos!
While the corners are chamfered to remove the sharp edge, it’s to protect the wall, and not your kid. The sharp edges are prone to chipping and breaking…
Good to know! Thanks!
Very nice work. Was this a regular concrete mix? I ask because I’ve heard that self-consolidating concrete is often used with board formed.
Jackson, yes it was a standard mix. Hope this helps!
Yes, it does help! Thank you.
Hey there…. I like the valuable information you provide in your articles. I will bookmark your weblog and check again here frequently. I am quite sure I will learn many new stuff right here! Best of luck for the next! Thank you so much for sharing.
תבניות לבניה
Amazing. Love to try it.
You didnt explain how they attached the boards to the forms, and how they got boards onto the other form wall once one side is already up. seems pretty expensive to buy cedar but im sure a lot of old used wood is available what form release was used. was that wall supposed to have a curve or was it just not set yet
Itís difficult to find knowledgeable people in this particular topic, but you sound like you know what youíre talking about! Thanks
This website really has all the information I needed concerning this subject and didnít know who to ask.