Tags: #buildingenclosures #buildingenvelopes #buildingmaterials #buildingproducts #buildingscience #materialsscience

Are two WRBs better than one? I’m asked this question routinely, and invariably it involves wood-based integrated WRB panels. 

Here, we see building paper applied over the integrated panel. A common approach. But being common doesn’t necessarily make it right. This strategy must account for three important factors. 

– The hundreds/thousands of staples that penetrate the underlying panel potentially invite water behind its overlay and into the OSB strands. Remember, this panel isn’t just OSB, it’s OSB with an overlay. And that overlay is porous and dynamic. 

– There is an explicit need to consistently flash to the outer paper, not the inner panel. In this case, there are some real challenges that will likely prevent that. Interfaces resulting from work sequence issues are particularly relevant. 

– Account for additional moisture burden between the two systems – a factor compounded by the building’s beachfront location. 

Building more intuitively seems harmless enough, but obvious risks often go unrecognized without appreciation for what materials can and cannot do – whether in isolation or when brought together. History will likely answer this particular question. Until then, I’m looking forward to exploring this further.