My non-DoD research led me to this,
When Are Construction Materials Subject to Sales Tax?
In most states, construction contractors must pay sales tax when they purchase materials used in construction. This means that any materials and supplies you purchase are taxable at the time of purchase. However, you won't have to pay sales or use tax upon the sale of the finished construction. In some cases, this can be an advantage because any markup you charge to your customer on the materials, supplies and labor, won't be subject to sales tax.
Again, I am not a construction contractor, but rather mostly a supply contractor, so this is all foreign to me. Does the above paragraph apply to federal construction contracts? (assuming the contract is in one of the "most states?"