How to Install a Soffit on a Porch Ceiling

Written by mark morris
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How to Install a Soffit on a Porch Ceiling
Add a coat of primer and two coats of paint to your finished soffit. (paint roller image by Ana de Sousa from

A soffit is the flat panel that extends out from the wall of the house and covers the underside of the rafters in most contemporary houses. It is usually made from ¼-inch lauan plywood. Since you will be working overhead, you'll need a helper and at least two stepladders, or a scaffold. The best way to hang the soffit is with a compressor and an air stapler. Precise measurements and accurate cuts are essential to a quality soffit installation.

Skill level:

Things you need

  • 1/4 inch plywood
  • Tape measure
  • Circular saw
  • 1-by-1/4 inch flat screen mould
  • 1-inch staples
  • Painter's caulk
  • Oil-based primer
  • Latex paint
  • Medium-nap roller
  • Extension handle

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  1. 1

    Calculate the area of the ceiling above the porch. You'll need enough ¼-inch plywood to cover the entire area plus 15 per cent for waste. You'll also need enough screen mould to cover all of the joints between the plywood pieces.

  2. 2

    Cut the first sheet of plywood to fit in one corner of the porch. Cut it so that the side away from the wall ends in the centre of a rafter. Run the plywood with the long side parallel with the rafters. Cut the plywood to length to fit between the inside of the fascia and wall of the house. Fascia is the flat board that runs along the outside edge of the roof, covering the rafter ends.

  3. 3

    Lift the first piece into place and staple it to the rafters, with 1-inch staples, spaced approximately 10 inches apart. Position the next piece butted up to the first. Rafters are installed with a space of 16 inches from centre to centre. Attach the second piece to the rafter the first piece ended on. Its opposite edge will fall in the centre of the third rafter over. Staple it to the four rafters, one along each edge and two in the centre of the panel, stapling every 10 inches along each rafter. Continue adding pieces until the next to last piece. Measure the remaining distance and cut the plywood to fit the width.

  4. 4

    Staple a strip of 1-by-1/4-inch flat-screen mould to cover every seam between plywood panels in the soffit and staple them over the seams. Cut a 10-inch-square hole every 8 feet, 10 inches in from the edge of the roof , through the plywood, for soffit vents, with a jigsaw. Position the holes parallel with the outside edge and 2 inches in from the back of the fascia.

  5. 5

    Roll a coat of oil-based primer over the entire surface of the new soffit with a medium-nap roller and an extension handle. Caulk the edges of each panel with latex painter's caulk. Allow the caulk and primer to dry thoroughly and apply two coats of exterior latex paint to match the house colours. Insert a soffit vent grille into each hole you cut along the edge of the roof.

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