How to Size a T Plate
Choosing a wood connector size for exposed beams
“How do I choose a wood connector size for my exposed beams?” This is one of the most common questions home owners and builders have when trying to incorporate decorative or structural iron beam straps with timbers. For new construction an engineer or an architect will specify the requirements for your application including a minimum thickness, size, and width for the iron face plates. Most importantly they will specify the diameter and length of the fasteners (bolts or lags) used to attach the wood construction tie, which is what determines the structural value of the post beam connection. For instance, a bolt can be rated as a structural grade 8, since it is bolted through the beam with a nut on the other end, whereas a lag has a pull out value which only allows it to be rated as a grade 5 in structural integrity. The larger the diameter and the longer the lag, the more structural the fastener will be.
On determining what size of a custom iron face plate to add to an existing beam structure that you want additional support or even if the iron brackets are being added for a purely decorative purpose, you should keep in mind that you are simulating a structural beam support. It is best to make the size large enough to appear that it has a true structural value. I have found that the most efficient way to choose a size for a construction tie or decorative beam plate is to cut a template out of paper or cardboard and tape/staple/ or tack it to your beam. Start with 2” wide and 8” long or tall. (The measurement is from end to end.) Another good tip would be to use black poster board or paint your template black to be able to visualize it better, but don’t worry about cutting the actual design, you are only worried about the basic size.
Look at the example above, as you can see the simulated cutout is too small all the way around and too short. The bottom arm of the T does not go far enough down on the post to be or appear structural, nor does it look wide enough. As a rough guide, I would suggest 4 ½” from the end of the post, then you have to take the width of the beam into consideration as well. In the image below the beam is 9 ½” tall and the post is 7 ½” wide. The Strap is 4 ½” wide and the 20” on the horizontal and 26” vertical. Again it is all personal preference on how bulky you want your strap. I hope this information helps in your quest to find the correct size for your application.