How to Replace a Rotten Fascia Board and Rehang the Gutters
Rot shows on the front, but it starts at the top and the back. Cut it all out, fix the cause and prime every face of the new board.
- Advanced
- 4 to 8 hours for a typical house
- Updated
The short answer
Replace a rotten fascia by supporting or removing the gutters, pulling the drip edge and lower shingle course if needed, cutting out the rotten board back to sound wood on a rafter tail, checking and repairing the rafter ends and sub fascia, and fastening a primed replacement with 2-1/2 to 3 inch corrosion-resistant nails or screws into every rafter. Use scarf joints over a rafter, flash the top, and rehang the gutter.
Fascia is the trim board that runs along the ends of the rafters at the roof edge. The gutter hangs from it, the drip edge covers its top and the soffit meets its bottom. Because it sits at the very edge of the roof, it takes whatever water the roof and gutters fail to handle, and in the Fraser Valley, with months of steady rain and needles from fir and cedar clogging the gutters, it is one of the most common rot repairs on a house.
The front of a fascia often looks sound while the back and top are soft. Water gets in from above where the drip edge is missing, from behind where the gutter is set wrong, or from overflow when the gutter is blocked. Painting over it does nothing. The job is to cut out everything that has decayed, check what is behind it, fix the cause, and install new wood that is sealed on every face.
This guide covers replacing the board and rehanging the gutters. For the metal that protects the top edge, see how to install drip edge and how to install gutter apron. For wrapping the new board in aluminum, see how to install aluminum fascia cladding. The fascia and soffit service page shows the full range of work.
Tools
- Pry bar and cat's paw
- Reciprocating saw
- Circular saw or mitre saw
- Cordless drill and driver
- Level and chalk line
- Tape measure
- Paint brush
- Caulk gun
- Ladder stabilizer and scaffold or ladder jacks
- Dust mask and eye protection
Materials
- Primed finger-jointed, cedar or PVC fascia boards, typically 1 by 6 or 1 by 8 or as matched to the old
- Exterior primer and paint, or pre-primed boards
- Corrosion-resistant nails or exterior screws, 2-1/2 to 3 inch
- Replacement rafter tail lumber or sistering pieces
- Drip edge or gutter apron
- Exterior-grade sealant
- Gutter hangers and sealant for re-hanging
Safety first
- Work from a stable scaffold, ladder stabilizer or a lift, tied off. Fascia work is done at the eave, at the edge of a fall.
- Houses built before about 1990 may have lead paint on the fascia, and some older materials contain asbestos. Test before sanding or cutting old paint or soffit materials.
- Gutters full of water and debris are heavy. Support them before loosening hangers.
- Cut boards away from the ladder and keep tools on a belt, not on the ladder top.
Step by Step
Step 1: Find the extent of the rot and the cause
Press a screwdriver into the top edge, the back, and the bottom of the fascia, and into the ends of the rafters behind it. Mark soft areas. Then trace the cause: overflowing gutters, a missing drip edge, shingles that stop short of the edge, a leak at a valley or a gutter sloped toward the house. Replacing wood without fixing the cause brings the rot back in a few winters.
Look above at the roof edge, and inside the attic for stains near the eaves. See how to inspect a roof deck for rot if the damage reaches the deck.
Step 2: Support or remove the gutters
Mark the gutter slope and the downspout positions before loosening anything, so you can rehang at the same height and fall. Remove hangers or spikes and lift the gutter off. On long runs, have a helper support it and tie it off to a stable point. If the gutter is old or damaged, this is the time to replace it.
Do not leave a heavy gutter hanging from one or two hangers. It bends and sometimes tears the fascia you want to keep.
Step 3: Free the top edge and remove the rotten board
Loosen the drip edge and the lowest row of shingles at the nails so the fascia top can come free. Pry the board from the rafter tails, working from the nail locations, or cut it in sections with a reciprocating saw. Cut the rotten board back to solid wood, ideally ending at the centre of a rafter tail, so the new board has a landing.
Collect old nails and debris, and dispose of old material properly. Take care of any lead paint dust.
Step 4: Repair the rafter tails and sub fascia
Sub fascia, where present, is a backing board behind the fascia, often on older houses or with the soffit framing. If it is soft, replace it. Rafter tails that have gone soft at the end can be cut back and sistered with new lumber, fastened with construction adhesive and screws, so the new fascia has a solid surface. Coat the cut ends with wood preservative.
If rot has reached the deck edge, replace that strip of sheathing first. See how to replace rotten roof sheathing.
Watch out: Do not cover rot or cut through load-bearing framing. If the rot runs deep into rafters or the top plate, have a carpenter or engineer assess it.
Step 5: Prime every face of the new board
Rot starts on faces you cannot see later. Brush primer on the back, the top and the ends, as well as the front, and let it dry. Cut ends, where wood is most absorbent, get a second coat. Use pre-primed finger-jointed boards, cedar, or PVC trim for extra durability. PVC trim needs no paint for rot protection but needs to be fastened with room to expand.
Step 6: Fasten the new board and join the ends over a rafter
Hold the board tight to the rafter tails, with its top at or slightly below the plane of the roof deck so the drip edge and shingles sit on it properly. Fasten with two 2-1/2 to 3 inch nails or screws at each rafter, staggered top and bottom, and pre-drill near the ends to prevent splitting. Keep the fasteners back from the ends.
When a joint is needed, cut both ends at 45 degrees over the centre of a rafter tail, so the joint is supported and sheds water, and glue it with exterior adhesive. Butt joints open up and let water in. Leave a small gap if the board is PVC, to allow for expansion.
Tip: Dry-fit the board and check it with a level and chalk line before you fasten it. A crooked fascia shows from the street.
Step 7: Reinstall the drip edge and flash the top
The top edge of the fascia is where water attacks, so metal must cover it. At the eaves the flashing goes under the membrane, as described in how to install drip edge. Re-nail the lifted shingles and reseal them, and seal any nail heads that show. Caulk the joints and nail heads on the face.
Step 8: Paint, then rehang the eavestrough
Paint the front, and the bottom edge, in two coats. Rehang the gutter with hangers or brackets every 24 to 36 inches (closer in snowy areas), sloped toward the downspouts about 1/16 to 1/8 inch per foot. Seal end caps and joints, and run water through to check the flow. Make sure the back lip sits under the apron or drip edge leg, and that no water runs behind it.
Why Fascia Rots
- Overflowing gutters push water over the back lip and behind the board.
- No drip edge or apron lets water run behind the gutter and down the face.
- Shingles that stop short of the edge leave the top of the board exposed.
- Bare end grain soaks up water. Always prime cut ends.
- Gutters hung with the wrong slope hold standing water against the wood.
Board Choices
Primed finger-jointed pine is cheap and paints well but rots if the paint fails. Cedar resists rot better. PVC trim boards do not rot and hold paint well, but they move with temperature and need gapped joints. Match the thickness and width of the old board so the gutter, the soffit and the drip edge still line up.
Common Mistakes
- Replacing only the visible rot. The decay continues behind and under it, and the new board fails next to the old damage.
- Not fixing the cause. A clogged gutter or missing drip edge rots the new board too.
- Bare end grain and backs. Unprimed faces soak water and rot from the inside.
- Butt joints between rafters. They open and let water in. Use a scarf joint centred on a rafter.
- Fastening too close to the ends. The board splits and the joint opens.
- Leaving the top exposed. Without drip edge over the top, water gets behind the gutter again.
When to Call a Professional
If the rot runs into the rafters, the soffit framing or the top of the wall, if the fascia is high or the house has a complex roofline, or if old paint may contain lead, call a roofer or a carpenter. Fascia work is done at the edge of a fall and often needs scaffolding or a lift.
A contractor can also replace the gutters, repair the drip edge and check the roof edge in one visit, which is usually where the rot started.
Fraser Roofing does free roof inspections across the Fraser Valley, from Hope to Abbotsford. See our Fascia and Soffit service or the towns we cover.
How to Replace a Rotten Fascia Board: Questions
Why is my fascia board rotting?
Most fascia rots because water is getting behind or on top of it. Common causes are overflowing or clogged gutters, a missing drip edge or gutter apron, shingles that stop short of the roof edge, bare end grain and poor paint. Wood that stays wet through a long winter softens from the top and back first.
Do you have to remove the gutters to replace fascia?
Usually yes, or at least lower and support them, because the gutter hangs from the fascia board being replaced. Mark the slope and the hanger positions first so the gutter can be rehung at the same height and fall. Replacing rotten gutters at the same time is sensible since they are off.
What is sub fascia?
Sub fascia is a backing board fastened to the rafter tails behind the visible fascia board. It gives a flat, solid surface for the fascia and the gutter hangers, and helps close the gap between the rafters. If it is rotten it has to be replaced too, because the new fascia depends on it for fastening.
What is the best material for replacement fascia?
It depends on budget and the look wanted. Primed finger-jointed pine is inexpensive and paints well but relies on paint to resist rot. Cedar lasts longer. PVC trim does not rot and holds paint, though it expands and contracts so joints need gaps. Whichever you choose, prime every face and cut end of wood boards.
How do you join two fascia boards?
Cut both ends at matching 45 degree angles, called a scarf joint, so they overlap, and centre the joint on a rafter tail so it is fully supported. Glue it with exterior adhesive and fasten through both boards into the rafter. A butt joint opens as the wood moves and lets water in.
Related Guides
All Roof Edges, Fascia and Soffit guides|The full How-To Library
This guide is general education. Always follow the product manufacturer's installation instructions, the BC Building Code and WorkSafeBC requirements, which take priority over anything written here.
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