Hempy Mortar to Reduce Cold-Bridging of Hemp Blocks

Hempy mortar is insulating which helps reduce heating and cooling costs. Featured on Hemp and Block’s Instagram 7/12/2023.

Prototype pics for what I’m calling “Hempy Mortar!”

How about using hemp and other insulating aggregate to create load bearing mortar (similar to a “Type N” mortar for above-grade masonry) with R value?? Yes I’m talking about eliminating any potential cold bridging that may happen with conventional cement:sand mortar.

How to make insulating hempy mortar

Here’s a mix design for hempy mortar that works great with hempcrete (hemp-lime) building. Just 3 ingredients:

  1. Our hempcrete binder
  2. Small pumice stones (ideally 1/4″ … 3/8″ tops)
  3. Hemp hurd fines (these are 1/4″ – 1/8″)

The pumice is used in place of sand to bring R value (insulation benefit) and compressive strength. Hemp hurd fines work real well as an insulating, “fine aggregate” that pairs well with the small pumice stones. Together, the hemp fines and pumice stones fill up the void space in the manner required when combining course and fine aggregates in a mix.

An example of a hempy mortar mix ratio by volume:

  • 1 part Hemp and Block hempcrete binder
  • 1 part insulating aggregate (such as small pumice stones)
  • 1 part hemp hurd fines
  • Enough water to make a workable mortar. Stiff enough that if you flick your trowel and turn it upside down, the mortar sticks to the trowel. Too soupy = weak mortar. Too dry = not workable enough.

Be sure to wear appropriate personal protective equipment when working with hydrated lime, cements, et cetera. Goggles, gloves, dusk mask and protective clothing!

Also, look at the hemp lime bond strength! In the image above, the top block being held is a lighter hempcrete mix, the block weighs 10 lbs. The bottom hemp block is denser and heavier at 25 lbs. Our Made in USA hempcrete binder is a proprietary blend of hydrated lime, natural pozzolan, and other minerals to make hemp blocks, hempcrete walls, floors and more. The time-tested combination of hydrated lime and pozzolans allows for masonry mortars that really stick when you need them to!

And being a big supporter of local economy…

You can also use foamed glass aggregate or similar instead of pumice if it’s closer to you. Pumice has many benefits and very eco-friendly… but I also use it because it’s within my region. If foamed glass or expanded clay are the only options near you, you can still make hempy mortar. This industry needs to stay evergreen and sustainable! That means buying local as possible.

Have any questions about hempy mortar and other hemp-lime building materials? Feel free to contact Hemp and Block anytime.

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