Starting at one end, prepare the ledger board for the joist hangers by measuring 250mm and marking with a pen on the lower edge of the ledger board 😉 This will be where the first ‘outside wall’ of the first joise hanger should be positioned 👍 Measure, from this mark, another 40mm and mark again. The joist hanginger’s width is 40mm. This marks the location of the second side. From this mark, you can measure another 680mm. Here is the location of the outside wall for the second joist-hunger. You can continue this procedure for each joist hunger. Then you’ll have the same length at one end of your ledger board, making it symetrical. 
8. Once the leadger is prepared with the location of the joists in it, you can drive the last structural fasteners. Builders used thicknesses of 1/2 inch in the past. lag screws in the solid home band. Today, 1/4-inch structural screws are the preferred choice. They are stronger and more resistant to shear than larger screws due to the fact that they are made from metal. There is no need for pilot holes to be predrilled. The type and length of the house rim to which you attach your structural screws will affect the spacing. Use nails when installing a ledger board. These nails aren’t designed for this purpose, and can become loose over time. 
These are the pros ozcobp.com Please provide additional information. I had had a friend who wanted to build a pergola but didn’t quite have the room for a four-post structure. He had a narrow entryway, which is typical for pergolas. It was okay. The beauty of pergolas lies in their versatility, I said to him. My suggestion was a two-post structure with the house supporting the posts. A pergola attached to a house is a great way to save money. space while providing the support the structure needs. With a few adjustments to the standard design, and the installation of a strong ledger board, your house can act as your pergola’s support. Edited by Edward Adams (Kachi, Pakistan) on August 29, 2021 
It is important to ensure that your deck is safe and secure when building your wooden decking. A ledger board can be used to attach wood decking structure to your house or an existing building. Or, you may build it unattached and create a standalone deck. Build decking using a ledger board eliminates the need for additional support beams and the need for supporting footings right up against the house Building. Because attached decking has more support for the floors joists of an existing building, bracing is less necessary. Something to bear in mind is that it’s not always possible to attach a ledger board to the exterior of some buildings if the walls aren’t strong or straight enough to attach a suitable ledger board.