Invisible join between two 200x200 beams on a support

Question

I'm an IT'er with some experience in woodworking, looking to build his own backyard porch. It should eventually look something like this;

I'm pondering now on how to make the connection between the large top front beams. They measure 200mm x 200mm and ideally I don't want to see any screws or bolts.

What I want to do: There should be two lag screws in each of the notches on either end of each beam that connect them to the vertical support. I can then fill the notch with a custom fit piece of wood. I can then also screw the custom fit piece to the beams for extra support from the top.

Do you think this will be strong enough? Are there any better idea's I'm missing? I find it hard to find any good resources on this.

Answer 1

There are a number of problems with your proposed design. Before you refine your design to conceal fasteners you should consider the structural needs that must be addressed.

• The beam across the front should act as a single continuous beam to hold the entire roof frame together. The construction of must be similar to any wood floor roof framing system. That means you cannot break the beam all the way through at each column. Part of the beam should be continuous at every point of its length. This can be accomplished by using multiple framing joists nailed/screwed together. a couple toe-nailed fasteners inside the column openings will not be adequate.
• The columns should attach to the beam at the top for the full height of the beam with multiple fasteners across its intersecting height. The frame may have a tendency to rack and the connection of the columns and beam are the only way you can resist the lateral forces. For the same reason, the right end should be securely attached to the building wall at the right and at the back.
• Although you do not discuss this in your question, the column bases must also be secured to a foundation of adequate depth for your climate to avoid any frost heave and to prevent anything that could bump it from moving the columns.

While it is possible to achieve these requirements without fasteners, the techniques require experience and skill. Rather than avoiding fasteners, you may want to consider concealing them. In wood framing of this size, you could easily recess connection bolts and provide wood plugs or artfully placed trim to cover the connections.