Technical guide · Pandaboard

WPC Fence: Post Spacing, Concrete Footings and Wind Load

A WPC fence is typically 1000–1800 mm high with 90×90 mm posts at 1800–2400 mm centers. Each post sits on its own concrete footing of at least 300×300 mm, embedded 600 mm or more and below local frost depth, finished 50 mm above grade with a slope away from the post. Top and bottom rails are fixed to the posts with stainless brackets and bolts, and pickets clip or screw on with 5–8 mm between them. Leave a 10 mm expansion joint every 6–8 m and where the run meets a wall; close up post spacing to 1500 mm in coastal or high-wind sites.

A WPC fence consists of posts, rails and slats. It looks like timber but needs no painting or preservative treatment. A fence is a wind-loaded structure: safety depends on the post foundation and the fixing method, not on the slats.

Safety prerequisiteWhere fence height is >1.5 m, the windward face is long, or the site is in a coastal typhoon zone, a concrete foundation and a wind-load check are mandatory. Fixing with plastic bases plus expansion bolts into paving is acceptable only for decorative fences up to 1.2 m.

01Key specifications and suitability

Suitable

• Garden and villa boundaries

• Community and park screening

• Pool and plant enclosure screens

• Terrace and balcony infill panels

• Commercial outdoor seating dividers

Not suitable

• Retaining walls carrying soil pressure

• Boundary walls above 1800 mm without structural design

• Roof decks in high wind where footings cannot be deepened

• Street boundaries exposed to vehicle impact

• Shorelines with permanent or tidal water

02Before Installation

2.1 Site survey

• Confirm the position of underground services (water, power, gas, drainage) — they must be located before excavation;

• Confirm the boundary line, fence alignment, corner and gate opening positions;

• Confirm ground type: soil (in-ground type) or concrete / stone (base-plate type);

• On coastal or open sites, check post spacing and embedment against the local basic wind pressure.

2.2 Materials and tools

Fence components, C20 concrete (or ready-mix), crushed-stone bedding, spirit level, tape measure, string line, shovel, rotary hammer, wrench, timber props, sealant.

Parts list and reference quantities：Per 100 m of fence, posts at 2000 mm, two rails; includes normal wastage.

2.3 Delivery and site conditioning

• Move panels indoors 24 h ahead and store flat; never lean them against a wall, which sets a permanent bow

• Keep one batch and one shade per elevation or room

• Spot-check 5 %: intact tongue or click, unmarked face, straightness within 2 mm over 1 m

• Cut and drill in a separate area and clear swarf at once so the face is not scratched

03Method 1: In-ground (soil, planting areas)

1. Set out - Run a string line along the boundary and mark each post position from the spacing; locate corners and gate openings separately.

2. Excavate - Pit size ≥300×300×800; place 100 of compacted crushed stone in the base.

3. Position posts - Insert the post, prop it in two directions with timber, and plumb it with a spirit level (≤2 mm/m).

4. Cast concrete - Place C20 concrete in layers with compaction, stopping 50 below ground level; finish the surface with a drainage fall.

5. Cure - Cure for ≥72 h (longer in cold weather). Do not knock the posts or fit slats during curing.

6. Fit rails - Install the top and bottom rails to the design level and fix them to the posts with stainless connectors.

7. Fit slats - Work from the bottom up or the top down, keeping the slat gap consistent at 20–50; leave a 3–5 expansion gap at both ends of each slat.

8. Fit post caps - Apply sealant inside the cap and press it on to keep rain out of the post.

9. Terminations - Fit trim at gate openings and corners; seal every cut end.

Never shorten the curing periodConcrete reaches only about 50 % strength at 3 days and about 70 % at 7 days. Fitting slats while it cures drags the posts out of plumb and there is no way to correct this later. Allow at least 72 h, preferably 7 days.

04Method 2: Base plate (hard surfaces)

1. Mark out - Snap lines for the post positions on the concrete, clear of services.

2. Fix the base plate - Anchor the plate with 4 × M10 expansion bolts, embedment ≥60; on tiled paving, drill through the glaze with a glass bit first.

3. Position the post - Insert the post into the plate, plumb it, then tighten the bolts.

4. Add bracing (tall fences) - Where height is >1.5 m or the windward face is long, add 45° braces or tie-back rods.

5. Fit rails and slats - As for the in-ground method, with a consistent slat gap.

6. Seal - Apply neutral silicone between plate and paving to stop water pooling and corrosion.

05Junctions and Details

• Corner posts: use a reinforced post or twin posts, each fixed independently in its own direction;

• Gate posts: increase the section or deepen the foundation (leaf weight plus opening impact);

• Junction with a wall: leave a 10–15 gap covered by trim; never force the fence hard against the wall;

• Changes of level: extend the posts at steps and cut the slats to follow the level, keeping ≥50 clear of the ground at the bottom;

• Drainage: seal the post caps and fall the top of the foundation so water cannot run down the post.

06Quality Acceptance

Table 6-1 — Acceptance requirements

07Common Problems

Table 7-1 — Typical defects

08Storage and Handling

Figure 2 — Stacking methods Store posts and slats flat in separate stacks on dunnage; support long lengths at several points to prevent bowing.

Table 8-1 — Storage conditions

Recommended stock life ≤12 months. Posts stored flat for long periods need multiple supports; discard any with mid-span sag >5 mm.

09Transport and Safety

• Load long lengths flat with supports ≤800 apart, lash them down and fit corner protectors at both ends;

• Avoid direct sun and rain;

• Locate underground services before excavation — never excavate blind;

• Wear gloves and goggles when handling concrete to avoid cement burns;

• Use a harness for work at height or near open edges, and set temporary warning signs while the fence is being installed.

10Appendix: Checklist

10.1 Goods receiving

• □Post, rail and slat specifications match the order

• □Same batch number, color difference acceptable

• □Profiles free of distortion, scratches and chipped edges

• □Hardware is stainless and complete

• □Post caps and trim present

10.2 Before installation

• □Underground services located

• □Boundary line and post positions confirmed

• □Foundation size and embedment depth as designed

• □Concrete and curing conditions available

• □Wind-load check complete (tall or coastal fences)

11Frequently asked questions

How deep should fence posts be?

At least 600 mm, and always below local frost depth so frost heave cannot lift the post. In soft ground, made-up ground or high-wind areas, go to 800–900 mm and enlarge the footing to 400×400 mm.

Can I bolt posts down with base plates instead?

Yes, if the slab is at least 100 mm thick and sound, with 6 mm base plates and four M10 anchors per post. On exposed boundaries an independent footing is safer; base plates suit low, sheltered screens.

What post spacing should I use?

1800–2400 mm. Thinner pickets, taller fences and higher wind pressures all call for the tight end of that range. Coastal, hilltop and gap sites should go to 1500 mm, or rails sag and pickets rattle.

Does a WPC fence need expansion joints?

Yes. Leave 10 mm every 6–8 m and where the run meets a wall or gate post, covered by a cap. WPC expands in summer, and a run pinned at both ends pushes its posts out of plumb.

Will a WPC fence rot or fade?

WPC does not rot, resists insects and needs no coating, but long UV exposure lightens the color as normal aging. Co-extruded boards carry a protective cap and fade more slowly. Washing with water limits staining and mold.

How do I install on a slope?

Step the fence. Keep posts plumb and rails level, cut pickets to suit each bay and put the level change at a post. Never bevel pickets to follow the slope, as the cut exposes the core and traps water.

About Pandaboard

Guangzhou Panda Commercial Development Co., Ltd. · Pandaboard / PEIDA

We manufacture and export gypsum board, mineral fiber and fiberglass ceiling tiles, calcium silicate and magnesium oxide boards, fiber cement board, aluminum ceilings, WPC and SPC wall panels, exterior decking, fencing and handrails, together with the matching grid and framing systems. The methods on this page are compiled from product behaviour and standard trade practice; for any project, follow the approved drawings, local codes and the specification confirmed on your order.

Website: www.pandamanufacturer.com Contact sales: contactus

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Guangzhou Panda Commercial Development Co., Ltd. · Pandaboard / PEIDA
This guide is technical information for specifiers and installers; it does not replace project drawings or local codes.