Technical guide · Pandaboard

Calcium Silicate Board: Framing, Screw Fixing and Jointing

Direct answer

Calcium silicate board is made from silica and lime under autoclave curing, typically 1220×2440 mm, 6–12 mm thick, with a density of 1.2–1.5 g/cm³; it is Class A1 non-combustible and moisture resistant. Fix it to light steel framing: C50 or C75 studs at 400–600 mm centers, furring at 400 mm, screws at 150–200 mm and 10–15 mm from the board edge, heads sunk 0.5–1 mm. Leave 3–5 mm between boards and treat the joint with compound and tape in two passes. Cut with a carbide blade — the dust load is high, so extract at the blade and wear a respirator.

Calcium silicate board is made from siliceous and calcareous materials under autoclave curing. It is Class A1 non-combustible, moisture resistant, dimensionally stable and strong, and is widely used for partitions, ceilings, service shafts and exterior wall sheathing. Installation is close to gypsum board, but the board is harder, heavier and generates more cutting dust.

How to read this document
· Calcium silicate board may be used in damp conditions, but it is not a substitute for a waterproof layer;
· The board is hard: cut it with a carbide-tipped blade — an ordinary utility knife will not score through it.

01Key specifications and suitability

Suitable

• Partitions in bathrooms and kitchens

• Ceilings and pipe boxing

• Corridor partitions in malls and schools

• Fire separation for shafts and plant rooms

• Exterior wall lining and facade backing

• Tile substrate where 8 mm or thicker

Not suitable

• Walls with heavy fixtures and no reinforcement

• Inside water tanks or permanently wet surfaces

• Curved or shaped details without custom work

• Large direct-bond areas without framing

• Temporary partitions that are moved often

02Before Installation

2.1 Site conditions

• The framing system is complete and accepted (see 11 Light Gauge Steel Framing);

• Ambient temperature ≥5 ℃, no rain during exterior work;

• Deliver boards 24 h in advance and store them flat;

• Confirm the access route — boards are heavy, so two people handle them.

2.2 Tools and protection

Carbide-blade cutter or dedicated shear, cordless drill, rotary hammer, self-drilling screws (galvanized), notched trowel, 2 m straightedge, vacuum extractor; PPE: KN95 mask, goggles, cut-resistant gloves.

2.3 Parts list and reference quantities

Per 100 m² of one face, studs at 400 mm; includes normal wastage.

2.4 Delivery and site conditioning

• Move boards indoors at least 24 h before installation and stack them flat on bearers at ≤600 mm centres so moisture content equalises with the room and shrinkage joints do not open later

• Use one batch and one shade per room or elevation; mixing batches shows as a visible colour difference

• Spot-check 5 % on arrival: flat face, intact edges, no blistering or scratches; reject boards with diagonal deviation over 2 mm

• Cut in a separate area, clear dust immediately and seal cut edges as described in this guide

03Method 1: Partitions

Figure 1 — Partition build-up Studs @400/600, joints landing on studs, staggered on the two faces; rock wool in the cavity.

1. Check the framing - Stud spacing 400 (8 mm board) or 600 (10 mm and above), plumb ≤3 mm/m, securely fixed.

2. Set out - Mark the joint lines; stagger joints by ≥300 and make sure every joint falls on a stud.

3. Pre-drill - Pre-drill 10–15 from the board edge with a bit slightly larger than the screw to prevent breakout.

4. Fix - Self-drilling screws φ4×25 at 150–200 spacing, 10–15 from the board edge, heads sunk 0.5 mm — do not overdrive.

5. Leave gaps - Board to board 3–5; board to structure 10, filled with sealant.

6. Jointing - Fill with jointing compound → apply joint tape (mesh) → second coat to level → sand.

7. Corners - Cut an L-shaped piece from a single board at corners and move the joint at least 300 away.

8. Finish - Skim and paint; in damp areas apply a moisture-resistant primer first.

Joint tape (paper/mesh) ≥100 wide3~5 joint, fill with compoundBoard face① Clean and fill the joint ② Bed the tape ③ Second coat to level ④ Sand and touch upJoint width: gypsum board 3~5; calcium silicate / cement board 3~5; MgO board 2~3; joints must land on framing

Figure 2 — Joint treatment 3~5 joint, compound fill, tape, second coat; calcium silicate joints must land on framing.

04Method 2: Ceilings

• Main runner U50, furring channel C50 @400 (8 mm board);

• The board is heavy: hanger points at 1000×1000;

• Joints fall on the furring channels, staggered ≥300;

• Screw spacing 150–200, heads flush and not overdriven;

• Apply a moisture-resistant coating to the ceiling in damp areas.

05Method 3: Exterior Sheathing

1. Install vertical framing - At the designed 400–600 spacing, fixed to the structure with connectors, leaving a 20 movement gap.

2. Install boards - Work from the bottom up, aligning joints with the framing, leaving 8–10 between boards.

3. Fix - Stainless or hot-dip galvanized screws at 200 spacing, at least 15 in from the board edge, never at a corner.

4. Seal - Backer rod plus neutral silicone in the joints, recessed 2–3.

5. Finish - Alkali-resistant primer plus exterior paint / texture coating, or the specified curtain wall system.

06Quality Acceptance

Table 6-1 — Permissible deviations

07Common Problems

Table 7-1 — Typical defects

08Storage and Handling

Figure 3 — Stacking methods Store flat, support at several points, keep clear of the ground; the board is hard and brittle, so control both stack height and support positions.

Table 8-1 — Storage conditions

09Transport and Safety

• Load flat with dunnage supports ≤600 apart, stack ≤1.2 m, secured with strapping;

• Cover with a rain tarpaulin;

• Cutting produces heavy dust: cut wet or with extraction and wear a KN95 mask;

• Board edges are sharp — wear cut-resistant gloves;

• Use a harness for work at height and never stand on the framing or the board face.

10Appendix: Checklist

10.1 Goods receiving

• □Size, thickness and density match the order

• □Faces flat, no cracks or missing corners

• □No moisture damage, no delamination

• □Edges straight, chamfers intact

• □Class A1 test report supplied with the goods

10.2 Before installation

• □Framing accepted, spacing suited to board thickness

• □Pre-drilling method agreed

• □Jointing materials on site

• □Dust extraction and PPE available

• □Access route clear

11Frequently asked questions

Calcium silicate or gypsum board — which is better?

Calcium silicate is non-combustible, moisture resistant and strong, so it suits kitchens, bathrooms, shafts and fire separation, but it is heavy, brittle and dusty to cut. Gypsum is light, easy to work and cheaper for dry-room partitions. Choose calcium silicate where moisture or fire performance matters.

Can calcium silicate board be used outdoors?

Yes, as part of an exterior system: 8–12 mm board, closer framing with corrosion protection, a drained cavity with a breather membrane, and weatherproof sealant over a backer rod. Interior board fixed straight to a facade will crack.

Why leave a 3–5 mm joint?

The board moves slightly with moisture and temperature, so the gap is both a movement allowance and a reservoir for the joint compound. Butted tight, the boards expand and crack the skim; filled and taped, the stress spreads across the full width of the tape.

Can tiles be fixed directly to the board?

Yes, with 8 mm board or thicker, framing closed up to 400 mm and a full-bed thin-set adhesive. The face must be dry and dust free, and a sealing primer reduces suction so the adhesive does not dry out and debond.

How do I keep the cutting dust down?

Use a carbide blade with dust extraction at the cut, or a hand-held cutter with a shroud. Score-and-snap only works on thin boards and leaves a rough edge. Screen the cutting area, wear an N95 mask and goggles, and wet-mop afterwards.

How heavy is the board?

At 1.2–1.5 g/cm³, 12 mm board weighs roughly 14–18 kg/m², so one 1220×2440 sheet is close to 45 kg. Two people lift every sheet; use a trolley for stairs and never carry, throw or lift by one corner.

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.