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15.5 Decking: Laying Deck Boards Around a Bump Out

While many homes have flat walls adjoining the deck, frequently the construction will have corners and “bump outs” for doors, windows, chimneys and other architectural features. The best way to install decking is from the outside edge in, so that any “scribed” pieces are ripped to width to fit along the wall of the house, so that the rough edge is hidden. Bump outs present a challenge to this.

Straight Decking

Decking around a bump out - where the house wall is not straight.

If your deck boards are being installed perpendicular to the frame and parallel to the house, lay the deck from the outside edge up to the bump out, leaving the pockets on either side for last.

Cut each piece of decking for the pockets to fit, mitering the ends if needed, similar to the illustration. Fit each piece and fasten it before installing the next to ensure a perfect fit. Lay full-width decking boards as far as you can, until the gap between the last board and the wall is too narrow for a full piece.

Measure the gap between the edge of the last full board and the wall at both ends and in at least one place in the middle of the section. Mark your deck board and cut to width using a jig saw, if the edge is not straight, or a circular saw for straight edge. Fit and fasten the last piece.

Angled Decking

Angled decking around a bump out.

If your decking is angled, or runs perpendicular to the wall, each piece will need to be cut at the end to fit against the wall.

  1. Lay decking up until the point that the bump out will interrupt the pattern, from end of the deck.
  2. Fit deck boards long enough to extend past the end of the deck and reach the wall.
  3. Measure and cut the ends to fit and install and fasten each board as you go to ensure the best fit.
  4. Install full-width boards as far as possible until the gap between the last board and the bump out is too narrow for a full piece.
  5. Measure, mark and cut the final piece to fit against the bump out as described for straight decking.

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