Using Rebar Stakes with Earthbags
Questions answered by Kelly Hart

Q: Should one use rebar reinforcement every 2 feet driven vertically through the bags.

A: This is not reallly necessary, except perhaps where you want to tie the wall into a bond beam.

Q: Why is it OK to use rebar through a bag? Doesn't it weaken the bag too much?

A: There only a few circumstances where it may be necessary to do this, but actually puncturing the bag with rebar does not substantially weaken it, and the fill material rarely leaks out.

Q: I saw this in a video called "Making the Soweto Hospice with Volunteers" where they said that it was not necessary to use the barbed wire because of these rebar stakes. I decided to do it like this because it´s cheaper. I could not afford the barbed wire, but if you tell me thatIi definitely need the barbed wire I will try to get some money to buy it.

A: We post lots of videos and pages about many different earthbag projects just to give readers as much information as possible. Ultimately it is your choice to decide how you want to proceed. I would say that 99% of the earthbag projects that I know about have used barbed wire, partly because that is how Nader Khalili, the architect who first popularized this technique, did it. Using stakes does help stabilize the wall, but the wire is just a bit better I think, especially if there were ever an earthquake that affected the house.

Q: I read an idea of just using rebar instead of bard wire, I guess that would work. What do you think?

A: As for using rebar instead of barbed wire, this has not been proven over time to be as stable as barbed wire to keep a structure intact, so I am not sure how well it will work. If that rebar is also incorporated into the bond beam at the top, this will certainly help stabilize the building. I doubt that using rebar stakes is any more economical than barbed wire, and may be more costly.

Q: If I were using rebar to avoid building buttresses on straight walls, how far is it recommended for them to be apart in a non-seismic area?

A: Stabilizing a straight wall with rebar pounded down through the wall might work if that rebar is also embedded in a bond beam at the top of the wall. I would suggest doing this at perhaps 2 - 3 foot intervals. Otherwise, for reinforcing with external rebar, you can consult these specs.

Q: What's the longest rebar you've ever hammered into a wall? I just tried a 10' long half inch rebar and am very puzzled. I thought I tried this before but a long rebar was impossible. Starting gently, it was ok. Now, it was going into a low strength earthbag tamped just yesterday. Slipping a 3/4" inside diameter section of iron pipe around it that's just a couple feet shorter than the rebar made the rebar vibrate a lot less so you could pound harder. This issue of using long rebar is huge for engineers working on designs for high risk areas.

A: I've never tried to pound a 10' length of rebar. Owen and I usually recommend only pounding about half that length. Two 5' sections will overlap by 2' in the middle of an 8' wall, and that should be sufficient to adequately stiffen the wall.

Q: What gauge of rebar is acceptable (3/8”) for pinning? Does the rebar poke through the scoria bags easily enough to go straight down? Do I just need to pin the rows of bags that are below grade?

A: 3/8" would be a minimum; I prefer 1/2" rebar. The pins are very easily pounded through the bags. I would make the pins long enough to go through most of the base course.

Q: We are using long spools of bag material instead of small, modular sized bags. Could we then spread out rebar reinforcement farther due to fewer individual bags per course of wall?

A: The long tubes of material do make the structure more monolithic, so in some circumstances this might reduce the amount of vertical rebar used. The placement of such rebar adjacent to openings and corners would remain the same.

Q: When bracing corners, are steel reinforcements encouraged in addition to earthbag buttressing or as an alternative to buttresses?

A: I would suggest using the corner steel pins, even with buttressing, and this can often suffice without the buttressing.

Q: When creating metal lintels over windows according to your visuals, there are 60cm (24”) rebar holding the middle bond beam in place. Does that rebar have to be reaching a depth 30cm below the window opening, or would the reinforcement of the opening be an additional steel bar?

A: I think it would work to use just one pin on each side of the window that served to both anchor the bond beam and reinforce the window opening, and in this case it would be best for that pin to extend below the base of the window.

Q: In my design,  earthbag walls are around 4 meters high, so is it necessary to put vertical reinforcements on the corners.

A: Vertical reinforcement would be necessary with walls that high.

Q: Is rebar thru gravel bags necessary?

A: Not for just a few courses, but higher walls would benefit.

Below grade?

Not really.


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