This is the question of the day-should 2A or 2B be used for wall or paver base? First, I’ll explain the difference. 2A and 2B are Pennsylvania classifications of crushed limestone. 2A limestone (also called dense grade) has finer particles and does not readily allow water to pass through. 2B (also called open grade) does not have the fine particles and allows water to freely drain through. Over the last few years I have taken notice of an industry switch from 2A to 2B.
The benefits are endless states the open grade crowd!
It’s faster to install.
Doesn’t freeze.
Doesn’t need large compactors.
Well, I would push back on this. Yes, it is easier to compact and is cheaper to install, but they miss one extremely important thing: drainage. When open grade 2B is installed without regard to drainage you are asking for trouble. I know this for a fact.
The Lesson
I am my own case study. Back before this was the norm, I was an extremely early adopter of this method (before most of these current companies were even in business). I installed open grade at my own house and I have to say, it has been nothing but trouble. This was a large project that involved completely replacing the foundation including the footer, adding a concrete driveway and a retaining wall with incorporated steps. The entire scope was constructed using open grade/2B limestone. What happens is when it rains and water gets into the retaining wall? It flows under the driveway, under the foundation footer and eventually into my basement. I have since installed a basement drainage system to allow the water somewhere to go. I believe this could have been prevented if I hadn’t installed open grade/2B limestone for the entire project.
In closing, I strongly recommend that you never use open grade /2B limestone within 10 foot of a dwelling.