Cutting Lap Joints
The easiest way to cut notches in lumber is by cutting a series of slots 1/4” apart using a saw, then remove the waste using a chisel and mallet. The challenge with the floor and porch timbers in this cabin design is their depth. This wood is too wide to be notched using any hand-held electric circular saw. These tools typically only cut 2 1/4” deep, which isn’t nearly deep enough to cut half way through a 12”-tall timber. In this case you don’t have any choice but to use a chainsaw. Mark the location of all notches using a square a fresh Sharpie felt-tip marker (it shows up better than a pencil on rough timbers), then make your cuts using multiple plunges with your chainsaw. You’ll need to be careful not to cut too deeply, but that’s not difficult.
VIDEO: Cutting Lap Joints
Is it possible to get away with a timber rim made from smaller wood? Yes, but that would mean adding another row of foundation piers down the middle of the cabin. I figure that’s an option that’s probably less inviting than buying and handling with a bit more wood, but you decide for yourself. You’ll find 6×8 or 8×8 beams around the perimeter, along with 2×8 floor joists (instead of the 2x12s in the plan) are strong enough when used with a central row of foundations piers and a central beam.
VIDEO: Anchoring Floor Frame Timbers
Be sure to take a look at the previous video. It explains the important step of securing your timber rim to your foundation piers. With the timber rim parts cut and fitted together, measure, mark and drill 3/4” diameter holes down through your 8x12s for the 5/8” diameter threaded rod anchors that’ll hold them to the foundation piers. Although you could just rest the beams on top of your foundation piers and hope for no really high winds, it’s safer to anchor things. Place the timbers in position over the piers, then use the holes in the wood to mark the locations for the holes you need to bore in the masonry. Remove the timbers, then use a rotary hammer to bore 1 1/2” to 2” diameter holes in the top of the foundation piers where you marked them. The purpose of these holes is to anchor the 5/8” threaded rods that will hold the timbers down, and we used a product called anchoring cement to make this happen.
Just so you know, the only beam you shouldn’t anchor just yet is the porch beam closest to the cabin. The plans show how it’s separated from the cabin beam by 3” to allow wall siding to extend down seamlessly to the bottom of the front cabin wall. That’s why the porch beam closest to the cabin goes in later. After the siding is applied, this beam is simply spiked into position in the notches of the porch side beams.
Here’s how I use anchoring cement for securing metal rods into foundation piers. It’s a powder you mix with water to form a thick liquid. It hardens in 10 minutes or so, and that’s why this procedure makes sense for anchoring beams to piers on this cabin:
1. Cut 10 lengths of 5/8” diameter threaded rod 30 inches long.
2. Thread a nut and flat washer onto one end of each rod and set one rod near each hole.
3. Mix enough anchoring cement to half fill 2 or 3 holes.
4. Pour enough of the liquid cement to fill the hole in one pier about 2/3 of the way to the top.
5. Move the timber into position over the hole in the foundation, then use a sledge hammer to tap the rod down into the hole and into the liquid anchoring cement.
6. Repeat the process for neighboring holes, being careful not to disturb the first rod.
7. When the anchoring cement has cured as long as necessary to be completely hard, tighten the nuts moderately, double-check that the tops of all beams are level and in the same plane as they should be. Loosen the nuts and add shims if needed to make all beams level.
8. Use a hacksaw to remove any threaded rod that extends higher than the top of the beams.