If you choose to be an owner/builder for your timber frame house, you will be doing a lot of purchasing of materials. You will likely get to know your local hardware stores well. You may even get on a first name basis with the employees of the big box stores. It can be both fun and terrifying at the same time figuring out not only what products to get, but where to get them from.
What to Get
We were interested in using some newer technologies in building materials that were not available in the Home Depot or Lowes stores. Therefore, we spent a decent amount of time on the internet researching products and

Where to Get the Stuff
Many new owner/builders assume that Lowes or Home Depot (the big box stores) will always have the least expensive price on materials. While it is frequently true, it is certainly not always true and there are other factors to consider when deciding where to buy building materials.
You can often buy directly from the producer, thus skipping the middle man, and save a fair bit of money. For example, we bought our cedar shingle siding directly from a family owned mill in Maine and had it shipped to our house site. Not only did we get to deal with really nice people who were familiar with our order, we got a superior product for less money.
Small, locally owned hardware stores are also a great option. One local family owned store delivered any purchase over $50 for free. Since we live 45 min from the supply stores, this option saved us a lot of time, effort, and gas. They also often will give discounts to owners who are building their own timber frame homes; remember it never hurts to ask.
Single supply houses (electrical, plumbing, etc…) are also another good option. These are especially helpful if you have questions as they will usually lend a great deal of support. They will also frequently extend the contractor rate to owner/builders – make sure you are friendly and respect that they normally deal with pros and you will get a better price.
No matter where you end up purchasing your building supplies, planning ahead can save you a lot of time. Having a general idea of all the plumbing supplies you need for a particular project before you’re in the aisle will make the process easier. Last, don’t forget to save your receipts, not only to keep track of your budget, but also to return any extra pieces that you didn’t need.