Well, because I've tried it. You notice you said mortar and not PC. I don't believe PC will stick to OSB as well as mortar. The reason I know mortar will stick to painted OSB is I've tried it and the reason it sticks is because weathered OSB is very rough even after being painted, the paint just help seal the OSB from the possilibility of water getting through the PC stones, the mortar on the back sides of the stones that holds the stones to the mortar applied to the chickenwire or wire mesh, which ever I can afford to use. If you think about it, what do we think will help protect PC walls from the weather? Sand and Cement mixture, right? So if that is true, then sand and cement (mortar) should protect OSB, especially painted OSB from what ever small chance of moisture from getting through all those layers of PC, mortar and more mortar and paint. If the weather has not done great harm to my OSB after two years of rain and snow and no paint, then I don't believe it will get through those layers and do any more harm. I feel pretty sure that mortar applied to chicken wire or wire mesh screwed to the studs rather than just the OSB will hold much better than mortar applied to chicken wire or wire mesh screwed to the OSB under tar paper, the reason it would be just screwed to the OSB once the tar paper is applied is because you can no longer see the studs once the tar paper is in place, I quite sure one could figure out where the studs are by measuring but I want the mortar to grab hold of the painted OSB as well as the chickenwire or wire mesh, and in my mind the tar paper acts as a barrier and the resulting mortar and chickenwire or wire mesh would just be a shell supported only be the nails or screws to the OSB or studs if they can be located every time and there would be no contact with the actual structure, or OSB in this case. Years ago out in California (and maybe so today as well) tar paper was applied directly over the studs (no sheathing what so ever) and chickenwire was applied directly over the tar paper then stucco was applied, this makes sense because the tar paper acted as a backing for the stucco, 1. To keep the stucco from falling through and 2. To help keep moisture and wind out of the house because there was no sheathing.
BTB
--- In papercreters@yahoogroups.com, Neal Chabot <sire@...> wrote:
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> What makes you think that mortar adheres to OSB, especially after you paint it ?
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> Neal
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> ----- Original Message -----
> From: "countryatheartok" criswells.ok@...
> To: papercreters@yahoogroups.com
> Sent: Wednesday, August 11, 2010 8:02:41 AM
> Subject: [papercreters] Re: Just posted some new photos of new walls
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> Thanks, I am hoping I soon will be able to show how to install papercrete stones to be used as siding over the papercrete walls and over OSB. I contacted Kelly Hart at
> www.greenhomebuilding.com  and asked his advise as to whether or not he thought I should apply tar paper over the OSB before I installed chickwire or wire mesh and then apply a thin layer of morter and then after the thin layer is dry apply morter to back of my stones and stick them in place. He said he thought applying the tar paper would protect the OSB from moisture that might through the papercrete stones. I think I am going to not take the advise and just apply a good exterior paint to the OSB, which by the way has been exposed to the weather for at least 2 years not paint and with no real damage. In my mind if you apply tar paper over OSB and then chickenwire or wire mesh and then your thin layer of morter you are creating a shell that is only supported by the nails or screws that hold the chickenwire or wire mesh to the OSB, the tar paper would prevent the morter from adhereing to the OSB, which in my mind is what I want it to do, I don't want just the nail or screws alone to hold the morter and stones, I would feel more secure knowing that the morter and chickwire or wire mesh and screws as well as the OSB are all holding the morter and stones.Â
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