Building cost premium estimate for best practices
I am building just north the St. Louis MO area. I’m certain, in absolute terms, labor and material costs vary significantly. What I expect though, is that there is a relationship between traditional building costs [I’ll define that in a minute in my area] and best practices [which I’ll try and define as best I understand]. So, how much of a premium, broken down between labor and material, as a % of cost is there to building best practices.
In this area, currently. traditional practices is a poured foundation, no insulation under the slab nor around the walls, with some form of water-proofing on the walls. Main structure is 2 x 4 construction with a vapor barrier on the interior and a WRB between siding and the sheathing. Fiberglass insulation in the exterior walls, R-13. Vented roof with soffits and peak vents. Insulation in the attic is a ‘crap shoot’ but consensus is probably R-20 or so.
Minimum Best Practices for Zone 5 [building a bit north of St Louis] would be poured foundation and slab. Either staggered double 2 x walls or 2 x walls with no vapor barrier and with some form of air barrier [spray closed cell, taped exterior foam sheet insulation, well crafted wrap of some type], same for the roof with the rule of thumb of 5-10-20-40-60 insulation. All things being equal, I’d like to use foam insulation on the exterior walls and roof.
I’ll be building where there are no required codes or inspections but also where I believe best practices will be unknown and unpracticed. I’m hoping to convince a builder to build to best practices and want to be able to anticipate what that premium might cost.
I’m sure there are a myriad of variables so I’m just seeking opinions and some general guesses of % cost differences, perhaps in your geographic region or particular expertise.