My husband and I are about half way through our build. There have been several unexpected costs that have popped up here and there....as I'm sure everyone can relate to all too well. For example, the builder thought we would only need one furnace seeing as our home is just under 3000 sq. ft. However, after we had signed the contract and gotten through framing, he met with his HVAC guy again who determined that 2 furnaces would be necessary due to our very open layout. When we got the invoice, it stated that the extra cost was $6800 plus an 18% GC markup. The markup was never made clear to us before. Now we are paying an 18% markup on everything that is ending up costing more than anticipated. So my question is, is this typical? Is this just the nature of home building?