How Many Samples When Testing for Asbestos?

[Dado Vucak]

Quick Background

Under contract on a 3 bed 1.5 bath ~1,400 square foot 1970s split level set to close this Friday, 9/17. The current strategy is "STR BRRRR". We're essentially taking it down to the studs and converting it to ~1,700 square foot 4/2.

Demo & Asbestos

We have demo scheduled in a couple weeks, however, prior to starting demo we decided to get an environmental study to test for asbestos in the building materials. The test consists of 10 random samples within the house including vinyl flooring, popcorn ceilings, wall texture (not drywall), pipe insulation, and and attic insulation.  

The results came back with only the popcorn ceiling containing 3-5% chrysotile asbestos which we'll have to get professionally removed. Not ideal but I guess that's why we factor in contingencies when doing renovations! 

Question

Given that we're tearing this down to the studs, and the fact that I will be responsible for the demo (not the contractor), I'm worried that the test did not include any samples of the drywall or the drywall mud/tape which we will be replacing and can very well have ACM . 

That being said, I have decided to get another test to include actual samples of the drywall and the mud/tape as well, however, I'm not sure how many sample are actually sufficient. Based on some quick Google searches sounds like 5 should be sufficient for the square footage of the house but at the end of the day it's just a gamble because it can be in one sheet but not the other 4 on the wall. 

What do you all think? How many drywall samples do you typically test for when doing demo and testing for asbestos?