Great info, so can I put the hempcrete inside of a center block wall structure and then also use it as a plaster on the outside of the center block and also on the interior
Hey! I would say it would be best to not sandwich hempcrete between concrete as you limit its ability to breath and therefore moisture can build. It would be best on either side of that wall as insulation and thermal envelope. If putting on exterior side you will need some additional layer to coat it (such as a lime plaster), on the interior you could leave it exposed but it can get "crumbly" if touched/bumped frequently so I recommend to either coat it interior as well or use a wall sheathing like MGO board or wood wool board to protect it (just dont use drywall!)
The frame we used is G90 coated so a little bit heavier duty than standard galvanized steel. It has held up really well and there is no signs of rust at this time. The main thing is you need to get past the initial cure which is several weeks long. During this time there will be a continuous moisture presence and that is what leads to deterioration. After it cures there is still moisture content but it is minimal, and as long its your material is not getting poured on regularly it should stay that way.
What’s the best mixture ratio of water hemp and lime to have an amazing non hurd falling hempcrete block? I am still failing a bit with making small blocks after drying under fan and sun. How much water and lime for a cup of hemp hurds is right? Thankss
It will depend on the lime you are using, I use a hydraulic lime that sets within 30-60 minutes. If you are using something off the shelf like an S lime it may need to sit up to 24hours for better strength. In any case, my go-to mix ratio (in weight) is approximately 52% water, 20% hurd, 28% lime. For more detailed smaller piece I may add a little extra water and lime for better cohesion within the block.
You should add clay to the mixture! Lime on its own won't give strength. Hydroulic lime is a lime that has clay in it. You can add metakaolin it will work perfect.
We used to use PVC cut to whatever length was needed to create the gap desired, now we usually use scrap wood blocks from framing. We typically just set the spacers in place until screws are in then pull the spacers so that when the form boards are pulled all you have is several tiny screw holes rather than larger gaps from your spacers that need to be filled in by hand
Good question. That is to create the necessary gap for your total wall thickness. For example, if you want a 9.5" thick wall your 2x4 will only make up 3.5" of that. You will need to create another 6" of gap in your forms, either all on one side or split on either side (which would put that 2x4 frame right in the center of the wall). So you use spacers like in the video to create whatever gap you need. It doesnt have to be left in the wall either, more times than not I just use scrap wood pieces cut to the length of the gap I need, then place those between the frame and formboard, then screw the formboard in place, then pull those scrap wood spacers out. After you finish your wall and remove your forms you will only have pin sized holes from your screws rather than 3/4" holes from using spacers like I did in the video. Hope this helps!
Thank you. That's really useful information.
Ty
Great info, so can I put the hempcrete inside of a center block wall structure and then also use it as a plaster on the outside of the center block and also on the interior
Hey! I would say it would be best to not sandwich hempcrete between concrete as you limit its ability to breath and therefore moisture can build. It would be best on either side of that wall as insulation and thermal envelope. If putting on exterior side you will need some additional layer to coat it (such as a lime plaster), on the interior you could leave it exposed but it can get "crumbly" if touched/bumped frequently so I recommend to either coat it interior as well or use a wall sheathing like MGO board or wood wool board to protect it (just dont use drywall!)
Would be interested in knowing if the steel frame is reacting with the lime as i am thinking of building a steel framed home
The frame we used is G90 coated so a little bit heavier duty than standard galvanized steel. It has held up really well and there is no signs of rust at this time. The main thing is you need to get past the initial cure which is several weeks long. During this time there will be a continuous moisture presence and that is what leads to deterioration. After it cures there is still moisture content but it is minimal, and as long its your material is not getting poured on regularly it should stay that way.
Are you planting industrial hemp to raise ?
Hey Randy, not at this time. Our goal is to utilize the hemp crops already being grown in our state for other purposes
What’s the best mixture ratio of water hemp and lime to have an amazing non hurd falling hempcrete block? I am still failing a bit with making small blocks after drying under fan and sun. How much water and lime for a cup of hemp hurds is right? Thankss
It will depend on the lime you are using, I use a hydraulic lime that sets within 30-60 minutes. If you are using something off the shelf like an S lime it may need to sit up to 24hours for better strength. In any case, my go-to mix ratio (in weight) is approximately 52% water, 20% hurd, 28% lime. For more detailed smaller piece I may add a little extra water and lime for better cohesion within the block.
You should add clay to the mixture! Lime on its own won't give strength. Hydroulic lime is a lime that has clay in it. You can add metakaolin it will work perfect.
Do people make 2 hemp Crete Walls
Where do you buy your lime?
Check out LimeWorks in PA
I meant do people make 2foot thick hemp Crete Walls
What are you using as spacers?
We used to use PVC cut to whatever length was needed to create the gap desired, now we usually use scrap wood blocks from framing. We typically just set the spacers in place until screws are in then pull the spacers so that when the form boards are pulled all you have is several tiny screw holes rather than larger gaps from your spacers that need to be filled in by hand
@@homelandhempcrete ... Maybe you could post a photo of that scrap wood spacer technique. Sounds interesting and innovative...
QUESTION @5:17 why do you need to add those?
Good question. That is to create the necessary gap for your total wall thickness. For example, if you want a 9.5" thick wall your 2x4 will only make up 3.5" of that. You will need to create another 6" of gap in your forms, either all on one side or split on either side (which would put that 2x4 frame right in the center of the wall). So you use spacers like in the video to create whatever gap you need. It doesnt have to be left in the wall either, more times than not I just use scrap wood pieces cut to the length of the gap I need, then place those between the frame and formboard, then screw the formboard in place, then pull those scrap wood spacers out. After you finish your wall and remove your forms you will only have pin sized holes from your screws rather than 3/4" holes from using spacers like I did in the video. Hope this helps!