Bolting Wood Beams Together

When joining pieces of wood together using a carriage bolt the square head on the bolt can become stripped in the hole making them hard to tighten.

Bolting wood beams together.

Stagger the bolts and make sure the bolts are placed a minimum of 2 1 2 inches from the edge of the beam. Be on the safe side when in doubt and use extra nails. A 2x10 beam should use a minimum of 4 3 nails fastened in a vertical pattern from both sides of the beam every 16 on center. Starting about 2 inches from the edges of the beam counterbore two holes on the inside or the least visible side of the beam for carriage bolt nuts.

The first method is an empirical method which is purely based on what has worked well in the past. Bolts must be closer than seven times the diameter or 80mm from the joist end and four times the diameter from the top and bottom. While code typically allows 3 8 inch diameter bolts for fastening braces to posts beams or joists i use 1 2 inch diameter bolts instead. To meet this requirement i bolt 2x4s to the posts approximately 2 feet below the bottom of the joists at a 45 degree angle to the beam and joists.

Connecting wood beams with through bolts is a safe and easy way to secure two wooden support beams together. Drill through the beam with a long bit the same diameter as the bolts. Images courtesy of eurocode 5 for example if two 47mm x 195mm are bolted together then m12 bolts should be used and positioned 48mm from the top and bottom and at least 48mm apart vertically if staggered fixings are used. To solve this problem insert a few finishing nails in the hole beside the bolt before hammering the bolt into place.

This course will feature a bolt design example utilizing awc s 2015 national design specification nds for wdc t tiwood construction. When securing 2 or more dimensional wood boards together to form a beam you will need to use the proper number and size nails to create a solid member.