While it's perfectly alright for a jazz musician to improvise, that approach doesn't always work as well in homebuilding. Architects, specifiers, engineers and product reps spend many hours collaboratively choosing the right materials for each job - and an abrupt substitution to save a few dollars can ironically be very costly in terms of callbacks, design underperformance and even code violations. "Ideally, all parties involved - the architect, builder and developer - have reviewed the spec before it's final and have agreed on all the products being used," says Karen Alves, LP Brand Marketing Associate. "That's because finding an 'equivalent' for siding or fire-rated sheathing involves not just the substrate but the codes that the product meets as well."