Fascia & Soffit Replacement
Step-by-step guide to replacing old timber fascia and soffit boards with low-maintenance PVC-U, including ventilation and gutter re-fixing.
Safety Warning — Working at Height
Fascia and soffit work involves extended periods at height. A scaffold tower is strongly recommended — ladder work is suitable only for very short sections. Follow the Work at Height Regulations 2005. Be aware of overhead power cables near rooflines. Wear a hard hat if removing rotten timber (it may fall unpredictably). Ensure the scaffold is on firm, level ground and correctly assembled.
What You'll Need
Tools
- Scaffold tower or mobile platform
- Crowbar and wrecking bar
- Circular saw or handsaw
- Drill/driver with countersink bit
- Spirit level
- Tape measure
- Snips or multi-tool for trimming
- Caulking gun
Materials
- PVC-U fascia boards (various widths)
- PVC-U soffit boards (flat or vented)
- Starter trims / F-section or J-section
- Corner joints and inline joints
- Stainless steel pins / poly-headed nails
- Ventilation strip or vented soffit panels
- Colour-matched silicone sealant
- Timber treatment (for rafter ends)
Technical Specifications
Step-by-Step Installation
1 Remove Existing Guttering
Carefully remove the existing guttering system — brackets, downpipes, and all fixings. If the guttering is being reused, label each section for re-fitting. If replacing, remove completely. Plug or cap any open downpipe connections to prevent debris falling into the drainage system during the works.
2 Strip Old Fascia and Soffit
Remove the old timber fascia board first, then the soffit. Use a crowbar and work carefully to avoid damaging the rafter ends. Old timber can be heavy and may break unpredictably — keep the area below clear. Remove all old nails, screws, and fixings from the rafter ends and wall plate. Bag and dispose of old timber responsibly.
3 Inspect and Treat Rafter Ends
With the old boards removed, inspect every rafter end for rot. This is the most important step. Any rotten timber must be cut back to sound wood and spliced with new treated timber. Rafter ends that are merely soft on the surface can be treated with wood hardener. All exposed timber should receive at least two coats of preservative treatment. Check that rafter ends are straight and aligned — pack or trim as needed to create a flat fixing surface.
4 Fit the Soffit Bearer and Wall Trim
Fix a wall-mounted receiver trim (J-section or F-section) along the wall where the soffit meets the brickwork. Fix with plugs and screws at 300mm centres, ensuring the trim is level. If the soffit span exceeds 200mm, install a soffit bearer (25mm × 50mm treated batten) along the underside of the rafter feet to provide mid-span support. The bearer prevents the soffit from sagging over time.
5 Install Soffit Boards
Cut soffit boards to width and slide the wall edge into the J-section or F-section trim. The outer edge will be held by the fascia board. Where the roof space requires ventilation (most pitched roofs do), use vented soffit boards or leave a continuous 5mm ventilation gap between the soffit and the wall. Approved Document C requires a minimum 25,000mm² of ventilation per metre run for cold roofs. Pin the soffit to the bearer with stainless steel pins at 300mm centres.
6 Fit the Fascia Board
Offer up the fascia board and fix to the rafter ends with stainless steel pins or poly-headed nails at 300mm centres. Drive fixings into the centre line of each rafter end. The fascia should overlap the top edge of the soffit and engage with the soffit support detail. Butt joint fascia boards using inline joint strips — leave a 3–5mm expansion gap at each joint. Use corner joints at external and internal angles. Ensure the fascia is straight and true along the full elevation.
7 Ensure Ventilation Compliance
Before fitting guttering, verify that the roof ventilation is adequate. For a cold pitched roof, you need a continuous 10mm gap at eaves level (equivalent to 25,000mm² per metre). This can be achieved through vented soffit boards, a continuous ventilation strip at the fascia/soffit junction, or eaves ventilation trays (over-fascia vents). Do not block ventilation when fitting gutter — use an over-fascia vent strip if needed.
8 Re-install Guttering and Finish
Re-fix guttering brackets to the new fascia following the gutter installation guide for your system (see our half-round or ogee guides). Apply colour-matched silicone sealant to any exposed joints, mitres, or cut edges where moisture could penetrate. Clean all boards with warm soapy water to remove handling marks and any construction dust. Stand back from ground level and inspect the full elevation for alignment.
Common Mistakes to Avoid
- Not treating rafter ends — If you cover rotten rafter ends with PVC, the rot continues and the fixing substrate fails. Always cut back to sound wood and treat.
- Blocking ventilation — A sealed soffit with no ventilation path leads to condensation in the roof space, which causes timber rot and mould. Ventilation is a Building Regulation requirement.
- Using steel nails — Standard steel nails will rust and stain white PVC within months. Always use stainless steel or poly-headed pins.
- No expansion gaps — PVC boards expand significantly in direct sun. Omitting the 3–5mm gap at joints causes buckling and warping in warm weather.
- Nailing too close to the edge — Fix pins at least 15mm from the board edge to prevent splitting. Nails too near the edge also create stress points.
- Cutting boards in cold weather — PVC becomes brittle below 5°C. Bring boards indoors to warm up before cutting, or use a fine-tooth blade at slow speed to prevent cracking.
Related Products
Need Technical Help?
Our technical support team can talk you through any installation query. Available Monday to Friday, 8am–5pm.
0121 693 0373 Contact Technical Support