J+J Enterprises
New Member
Hello All,
We built a hempcrete house in Vermont back in 2019 using Poraver's metakaolin product Metapor and hydrated lime as our binders. We're finally getting to plastering the exterior next month. We have a lot of extra binders leftover from our hempcrete build and have been using it to make up hydraulic lime plaster for patching and rendering as we close in areas forever.
We'd be super grateful for any wisdoms regarding our ratios for the exterior plaster. We've been using a 2:1 sand to binder ratio. And our binder has been 2 parts hydrated lime and 1 part metakoalin. We understand that the lime brings more water management/hygroscopic qualities and flexibility to the plaster and the pozzolan more strength and rigidity. So we just want to make sure we are using the most ideal ratio between the two for optimal performance of our exterior plaster in a Vermont climate.
Because we have a solid hempcrete base as our wall, our goal is to do just one 3/8" layer of plaster that has a fairly rough finish so that we have the option of adding additional layers down the road, or perhaps just a simple lime wash. Our plan is to use an air compressor spray gun to get the plaster on the wall and then knocking it back to mimic the old harling knock-back method.
Couple Questions:
1) In light of our context, would you say a 2:1 sand to binder ratio and a 2:1 lime to pozzolan ratio is ideal? (With a hempcrete base and a goal of a 1 coat layer of 3/8" plaster)
2) what do you folks recommend as the ideal sand type to use for our context? For our preliminary renders we have been using a play/beach sand from the gravel yard that has a good ratio of particle sizes/void ratio as well as a good amount of angular particles. But a friend of ours mentioned that it would be wise to use a "feed lime" powder mixed with masonry sand to encourage more like-with-like composition of the plaster. Given that we are doing a pozzolan lime plaster, would you say it's ideal to mix in some feed lime sand (which I'm assuming is a finer particle size) with the proper masonry sand or play sand or simply go with the masonry or play sand on its own?
All the Best,
Jon + Jesy
Barnard, VT
We built a hempcrete house in Vermont back in 2019 using Poraver's metakaolin product Metapor and hydrated lime as our binders. We're finally getting to plastering the exterior next month. We have a lot of extra binders leftover from our hempcrete build and have been using it to make up hydraulic lime plaster for patching and rendering as we close in areas forever.
We'd be super grateful for any wisdoms regarding our ratios for the exterior plaster. We've been using a 2:1 sand to binder ratio. And our binder has been 2 parts hydrated lime and 1 part metakoalin. We understand that the lime brings more water management/hygroscopic qualities and flexibility to the plaster and the pozzolan more strength and rigidity. So we just want to make sure we are using the most ideal ratio between the two for optimal performance of our exterior plaster in a Vermont climate.
Because we have a solid hempcrete base as our wall, our goal is to do just one 3/8" layer of plaster that has a fairly rough finish so that we have the option of adding additional layers down the road, or perhaps just a simple lime wash. Our plan is to use an air compressor spray gun to get the plaster on the wall and then knocking it back to mimic the old harling knock-back method.
Couple Questions:
1) In light of our context, would you say a 2:1 sand to binder ratio and a 2:1 lime to pozzolan ratio is ideal? (With a hempcrete base and a goal of a 1 coat layer of 3/8" plaster)
2) what do you folks recommend as the ideal sand type to use for our context? For our preliminary renders we have been using a play/beach sand from the gravel yard that has a good ratio of particle sizes/void ratio as well as a good amount of angular particles. But a friend of ours mentioned that it would be wise to use a "feed lime" powder mixed with masonry sand to encourage more like-with-like composition of the plaster. Given that we are doing a pozzolan lime plaster, would you say it's ideal to mix in some feed lime sand (which I'm assuming is a finer particle size) with the proper masonry sand or play sand or simply go with the masonry or play sand on its own?
All the Best,
Jon + Jesy
Barnard, VT
