USING BLOCKS IN A SLIP FORM WALL
Different sized blocks make a messy looking wall.
- This line of blocks will extend down the road as more batches are mixed, poured and cut.
Making blocks has always been my favorite part of working with papercrete. I think it’s because it’s something that can be done without the help of other people. I loved getting an early start, having all my stuff organized so I could move right along assembly line style. On a good day I could make about 10 mixer loads of blocks, one batch after the other in a long line down the road. I just got into a good zone. It’s like meditation.
I must admit that constructing a wall with the blocks was not enjoyable at all. It seemed like a lot of work and didn’t come out very well. I learned the hard way the importance of making uniform blocks. Mine were all different sizes so when they went into the wall the result had a definite “rustic” effect.
It was when I had the walls up to about 8 feet that I realized the job was too big for me so I decided to cut the main room in half. I would finish that room leaving the rest of the house as an an outdoor kitchen and patio. I set up forms to slip form this dividing wall and was amazed at how beautifully it turned out. Right then I knew I would not be stacking any more blocks into walls. I would slip form my next building entirely.
But what would I do with all those lest over blocks I had so enjoyed making? I had stacks of them all over the place.
Hundreds of blocks were stacked all over the site.
Cutting blocks to the width of the form. Slip form/ block wall behind me.
What I decided to do was use a hybrid method combining the blocks with slip forming. I took some blocks and cut them on the table saw to the exact width of the inside of the form. That way I could pour slurry into the form, drop a block down on top of it and add more slurry over it. This resulted in a nice uniform wall with texture provided by the courses of blocks embedded in the papercrete.
The first little building using this hybrid method came out great but I knew I could do better. For one thing the cutting of the blocks was time consuming and made a terrible mess.
This time I am leaving the blocks their original haphazard sizes. I am placing them in the wall on their sides so they are completely embedded in the slurry and are not visible in the finished wall.
The finished wall is really straight and uniform. More pictures next time.
One very definite of using the blocks this way (other than the time and mess involved in cutting all the blocks) is that it saves making fresh slurry. The blocks take up about half the volume of the wall. So this uses up a lot of blocks and I don’t have to mix up all the slurry it would take to slip form the walls.
The blocks are set upright in the form and will be completely embedded in papercrete.
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No that is the great advantage. I will say though that a lot depends on how you set up the forms. I found it best to pour all walls without any framing for doors and windows except a 4 foot opening for access while working. On my first little building I cut and framed the door to the finished size before pouring and notice now that there is a large crack at the corner of the door. On the second building I did as described and have had no cracks. My advice is to pour a few courses then frame in a smaller than finish size door. Use a good lintel over the door extending at least a foot on either side. Be sure to pour all around the corners without a break, especially over the door. Let the whole building cure for a couple of months or until it is really set up depending on your climate. Then come back in and cut out the openings with a chain saw. Be very careful when you do this to have a respirator or you will choke to death.
I have started getting ready to hang doors. The papercrete walls are strong enough to hold a door but you must reinforce before hanging. What I did was drill 3 holes on the door frame. I used the longest drill bit I could find, about 14″ I think and just the right size for the #4 rebar I am using. So I drilled the holes and quickly inserted the applicator tube for some expandable foam insulation. It’s the kind they sell to seal cracks. I immediately pushed and pounded the rebar into the hole and let it set up. That door frame is really in there now.
If you pour your papercrete as a monolithic structure you should have no problem with cracks. Be careful to keep it all a uniform width and do not let the forms interfere with its bonding to itself.
When you set up your forms leave as small an opening as is practical for access. Pour the whole building and let it cure for a few months then come back in with a chain saw and cut out the window and door openings. I have tried forming them before pouring but the papercrete shrinks away from the wood and tends to crack at the corners.
I will share a little secret with you. I have had some cracks along the roof line as a result of the reed ceiling material interfering with the bond. Anyway, I used some of that expanding spray foam insulation to fill them and all is well.
Hello, I am very interested in using recycled materials…… have ideas of using adobe and tires but I believe you were right, a person would never finish a project by themselves. How do I use a slip form? Can I use a rubble trench as a foundation? I would really be interested in pouring papercrete into a form and building it up layer by layer. How do I do this? Help! Thank you for your time. Nathan
Thanks for the note Nathan. Yes you can use a rubble trench foundation. If you google it you will come up with some good explanations and DIYs. I am using the slip forming method and find it the best for me. I used forms that I built out of plywood and 2x4s but think I will do it different next time. What we did was set up the forms and our the stuff in then go a round and move all the forms up. This was time consuming and not necessary. Next time I will make the forms out of 1’2 sheet of plywood so it will be a 4 foot square. I’ll keep pouring til it is full and then just have to move it up once. I think there are some pics in the blog somewhere. I made my framing and forms so all the wood can be removed and there are no breaks in the papercrete walls all the way around the building. You pour the walls solid, let them cure then come back in and cut out the doors and windows with a chain saw.