Truth is, many custom homes only come with the minimum warranty, which in most states lasts one year and covers all features. Modular manufacturers, on the other hand, go above and beyond with extended warranties (some at no cost) that cover workmanship, plumbing, electrical and other features. Best of all, many of these warranties include coverage for up to 15 years against structural defects. And yes, if you sell the home, these warranties are transferrable.