How to Anchor Wooden Decking to a Wall Securely

How to Anchor Wooden Decking to a Wall Securely

When it comes to building your wooden decking, it is vital that you ensure your deck is completely safe and secure. Wooden decking structures can be attached to your house (or an existing building) using a ledger board or built unattached, as a free standing 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 or building. Attached decking requires less bracing as they have more support to support the ends of the floor joists from the existing building. 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.

Please take time to read how to install a ledger board correctly to ensure that you have all the information you might need before you begin attaching your decking. Mistakes with other parts of the deck can be repaired relatively easily but the ledger board is one of the key steps to decking construction and could have disastrous consequences. Once anchored to the wall, the ledger board can’t be removed without disassembling the whole deck. Avoid this possible situation by taking time to anchor the decking to your wall correctly, making sure everything is level and attached using suitable fixings and techniques, as described below.

The Difference Between Free-standing or Ledger Board Decking

Free-standing Decking
Free-standing decking can be used away from an existing structure, or where irregular outside walls make it impossible to anchor the decking. A free standing deck can be built in any part of your garden and they also enable you to incorporate any existing features in your garden e.g. building your deck around a tree or existing landscaped featured. Free standing decking requires more structural timber and diagonal bracing to prevent it racking, providing more strength when in use.

Ledger Board Decking

Ledger board decking is used when the decked area is up against an existing building to which the ledger board is then bolted to keep the decking securely in place. Typically this would be where a door opens up into the garden space, often French or sliding patio doors. To ensure that no water penetrates the building via the ledger board, metal flashing should be installed carefully behind and on top of the ledger board so that moisture drains away from the building.

Materials for anchoring decking to a building

  • Pressure treated ledger board
  • Pencil
  • Circular saw
  • Measuring tape
  • Level
  • Chisel and hammer
  • Lag screws
  • Hot dipped galvanized (HDG) Nails
  • Hot dipped galvanized (HDG) washers
  • Hammer Drill with masonry bit
  • Paddle bit (one-inch)
  • Drip edge
  • Socket wrench
  • Anchor bolts and washers
  • Expansion anchors
  • Sealant gun with silicone sealant
  • Angled metal flashing (if attaching your deck to a brick wall)


Step by step guide

Decide where your ledger board needs to go. Measure the length of the ledger board required for the decking. Check that the pressure treated ledger board timber isn’t bowed or warped at all and cut to the required length. Offer the board up to the building and once satisfied that it fits and there are no obstacles that need to be avoided (e.g. cables or pipes), drill holes every 40cm (16 inches) all along the centre of the board. If there are obstacles on the wall to avoid, make sure to factor these into the bolt holes and move where necessary.

Line your ledger board up against your masonry wall checking that it’s level (you might need a second person to help you with this) and use a pencil to mark through your drilled ledger holes onto your wall.

Drill the marked wall to about a depth of 75mm (3 inches) to allow the lag screws to anchor properly to the wall. A hammer drill and a masonry matching the size of your lag screws / bolts will be required.

Place your expansion anchors into the pre drilled holes; you may need to tap them lightly with the hammer to ensure that they are completely flush with the wall.

Fit your ledger board to the masonry wall using lag screws approximately 125mm (5 inches) to take into account the thickness of the ledger board and provide a solid anchor into the wall. Screw them in through the ledger board into the expansion anchors, using washers in between the board and the screw heads and tighten up the screws. Avoid over tightening to prevent crushing the timber.

Using silicone sealant to seal the edges of the board and the drilled holes to prevent water penetration.

Once securely in place, building the decking can continue, safely and securely anchored to the building.

Common Mistakes to avoid

    • Using a ledger board that has badly bowed
    • Forgetting to use exterior grade silicone sealant around drilled holes
    • Measuring the height incorrectly or choosing the wrong location
    • Not using rust proof screws

TimberClick are able to recommend good quality tradesmen to carry out any work that you might be unable to do yourself. Please just ask and we will put you in touch with them.