Code of practice for construction of timber ceilings

IS 5390: Scope - Key Specifications & Tables

Scope:
IS 5390 covers specifications for timber ceilings, including recommended timber species, dimensions, and materials for framework and finishing.

1. Recommended Timber Species for Ceiling Boards (Appendix A)

• Examples:
  • Anjan (Hardwickia binata)
  • Chir (Pinus wallichiana)
  • Deodar London (Cedrus deodara)
  • Teak (Tectona grandis)
  • Rosewood (Dalbergia latifolia)
  • Sissoo (Dalbergia sissoo)
  • Gurjan (Dipterocarpus spp.)
  • Cypress (Cupressus torulosa)

(Full list in Appendix A)

2. Timber Dimensions for Ceiling Components (Clause 5.1, Table 1)

Note: Tolerance = -0 to +3 mm

3. Suspenders for Ceiling Framework (Clause 4.5)

• Material: Mild steel flats (IS:5986-1970) or other metals
• Dimensions: 35 to 65 mm length, 6 mm thickness
• Preferably two-piece for length adjustment
• Top end shaped for firm anchorage to structural floor

4. Units and Symbols (SI Units)

For detailed jointing, finishing, and preservation, refer to respective clauses and referenced IS codes.

flowchart LR
    A[Timber Species] --> B[Ceiling Boards]
    C[Dimensions] --> D[Framework, Planks, Beading]
    E[Suspenders] --> F[Steel

IS 5390: Definitions & Key Specifications Summary

1. Definitions:

• Refer to IS 707-1976 and IS 3670-1966 for timber-related definitions.
• Timber ceiling terms align with these standards and IS 5390 clauses.

2. Recommended Timber Species for Ceilings (Appendix A):

• Examples include:
  • Teak (Tectona grandis)
  • Deodar (Cedrus deodara)
  • Sissoo (Dalbergia sissoo)
  • Fir (Abies pindrow)
  • Rosewood (Dalbergia latifolia)
  • Others like Anjan, Cypress, Gurjan, etc.

3. Suspenders for Ceiling Framework (Clause 4.5):

• Material: Mild steel flats (IS 5986-1970).
• Dimensions: 35 to 65 mm length × 6 mm thickness.
• Preferably two-piece adjustable for ease of fixing.
• Top end shaped for firm suspension and anchorage.

4. Designer's Responsibilities (Clause 3.1.1):

• Specify timber type, thickness, grade, preservative treatment.
• Provide ceiling level datum, fixing method, underlay type.
• Detail treatment for junctions and finish (dressing/polish).

5. Units & Symbols (SI Units):

Quick Reference Table: Timber Species for Ceilings

flowchart TD
    A

IS 5390 — Key Specifications for Materials (Timber Ceilings)

1. Recommended Timber Species for Ceiling Boards (Appendix A)

• Examples: Teak, Sissoo, Rosewood, Deodar, Chir, Cypress, Fir, Gurjan, Anjan, Bijasal, etc.
• These species are durable and suitable for ceiling applications.

2. Timber Dimensions for Ceiling Components (Clause 5.1, Table 1)

• Tolerance: -0 to +3 mm on all dimensions.

3. Suspenders for Ceiling Framework (Clause 4.5)

• Material: Mild steel flats (IS: 5986-1970)
• Size: 35 to 65 mm length, 6 mm thickness
• Preferably two-piece for adjustable length and firm anchorage.

4. Standards Referenced for Timber Quality and Treatment

• IS 1708: Structural timber specifications
• IS 401: Maximum moisture content for timber
• IS 401 (Code of practice for seasoning)
• IS 401 (Code of practice for preservation)
• IS 6313 (Anti-termite measures)

Summary Diagram: Timber Ceiling Components

graph LR
A[Timber Scantling] -->|60-75 mm thick| B[Ceiling Framework]
C[Timber Planks] -->|15-20 mm thick| B
D[Beading] -->|12 mm thick| B
E[Mild Steel Suspenders] -->|35-65 mm length, 6 mm thick| B

Use these guidelines for selecting timber species, dimensions, and metal suspenders to ensure compliance with IS 5390 for timber ceilings.

IS 5390 - Types of Joints (Clause 6.1)

The longitudinal edges of planks can be jointed by:

1. Butt and Beading Type Joint (Fig. 1)

   • Planks are joined edge-to-edge with a beading strip for reinforcement.
   • All dimensions are in millimetres.

2. Overlap Type Joint (Fig. 2)

   • Each plank overlaps the adjoining plank by at least 15 mm on both sides.
   • This creates two levels at the joint.
   • Effective width of a plank reduces by at least 30 mm.
   • Dimensions in millimetres.

3. Half Lap Type Joint (Fig. 3)

   • Planks are joined by removing half the thickness at the joint edges and overlapping.
   • Ensures flush surface and better load transfer.
   • Dimensions in millimetres.

Summary Table

flowchart LR
    A[Planks] --> B[Butt and Beading Joint]
    A --> C[Overlap Joint]
    A --> D[Half Lap Joint]
    B --> E[Edge-to-edge + Beading]
    C --> F[Overlap ≥ 15 mm each side]
    D --> G[Half thickness removed]

All dimensions should be taken in millimetres as per IS 5390.

IS 5390: Manner of Fixing of Ceilings – Key Points

Types of Fixing (Clause 7.1)

• Ceilings fixed below roofs or floors to the underside of the frame.
• Fixing methods detailed in Clauses 7.1.2.1 to 7.1.2.5.
• Timber ceilings designed as per IS 883:1970 (Structural Timbers).

Tongued and Grooved Joints (Clause 6.1.4)

• Adjoining planks joined by tongue and groove for tight fit and stability.
• Tongue on one plank fits into groove on adjacent plank.
• Dimensions per Fig. 4 (typically: tongue width ~10-15 mm, groove depth ~10 mm).

Fixing Details

• Ceilings fixed using nails, screws, or adhesives as per recommended methods.
• Beadings fixed as per IS 2441:1984 for neat edges and joint covering.

Typical Tongue and Groove Joint Dimensions (mm)

flowchart LR
    A[Floor/Roof Frame] --> B[Horizontal Ceiling Frame]
    B --> C[Tongued & Grooved Planks]
    C --> D[Beadings fixed as per IS 2441]

Summary: Fix ceilings horizontally below floors/roofs using timber framing, join planks with tongue and groove joints for stability, and finish edges with beadings as per IS standards.

Fixing of Timber Planks to Ceiling Framework (IS 5390)

Key Specifications:

• Ceiling planks fixed directly to the underside of floor joists, ceiling joists, or trussed rafters (Clause 7.1.2.1, Fig. 5).
• For open ceilings, use timber fillets (~400 mm²) nailed to bridging joists or tie beams; planks nailed to fillets from below (Clause 7.1.3, Figs. 12-14).

Timber Dimensions (Clause 5.1, Table 1):

Tolerance: -0 to +3 mm

Fixing Details:

• Use nails or screws suitable for timber.
• Ensure planks are securely fixed to avoid sagging.
• Maintain spacing according to joist or truss spacing.

flowchart TD
    A[Floor Joists / Ceiling Joists] --> B[Timber Planks Fixed Directly Below]
    A --> C[Fillets (~400 mm²) Nailed to Joists]
    C --> D[Timber Planks Nailed to Fillets]

This ensures a stable ceiling with proper load transfer and aesthetic finish.

IS 5390: Finishing of Ceilings — Key Points & Specifications

Designer's Responsibilities (Clause 3.1.1)

The designer must specify:

• Type, species, and grade of timber ceiling.
• Thickness of the ceiling.
• Finished ceiling level relative to a datum.
• Preservative treatment details.
• Service penetrations through ceiling.
• Underlay type, if any.
• Fixing method.
• Junction treatment with adjacent ceilings.
• Dressing or polish needed.
• Contract conditions affecting ceiling work.

Types & Fixing Methods (Clause 7.1 & 7.1.2)

• Ceilings fixed directly to underside of roof/floor framework.
• Must follow design per IS 883-1970 (Structural timber design).
• Fixing methods include nailing, screwing, or using cleats as per sub-clauses.

Timber Dimensions & Species (Appendix A & Clause 2.1)

• Timber species and dimensions suitable for ceilings are standardized.
• Thickness typically ranges from 12 mm to 25 mm, depending on application.
• Alternate species allowed for planks (see Appendix A of IS 5390).

Additional Notes

• Final values for tests/analysis must be rounded as per IS 2-1960.
• Preservative treatment ensures durability against decay and insects.

Typical Fixing Method Diagram

graph LR
A[Roof/Floor Framework]
B[Timber Battens]
C[Ceiling Boards]

A --> B
B --> C

For detailed tables on species, grades, and dimensions, refer to Appendix A of IS 5390 and IS 883-1970 for structural design.

IS 5390: Recommended Timber Species and Dimensions for Timber Ceilings

1. Recommended Timber Species (Appendix A)

• Anjan (Hardwickia binata)
• Axlewood (Anogeissus latifolia)
• Bijasal (Pterocarpus marsupium)
• Chir (Pinus wallichiana)
• Cypress (Cupressus torulosa)
• Deodar (Cedrus deodara)
• Fir (Abies pindrow)
• Gurjan (Dipterocarpus spp.)
• Jarul (Lagerstroemia speciosa)
• Kail (Pinus excelsa)
• Kalasiris (Albizia odoratissima)
• Kasi (Bridelia retusa)
• Kindal (Terminalia paniculata)
• Kokko (Albizia lebbeck)
• Laurel (Terminalia tomentosa)
• Lendi (Lagerstroemia parviflora)
• Machilus (Machilus macrantha)
• Maniawga (Carallia brachiata)
• Pali (Palaquium ellipticum)
• Piney (Hardwickia pinnata)
• Rohini (Soymida febrifuga)
• Rosewood (Dalbergia latifolia)
• Satinwood (Chloroxylon swietenia)
• Sissoo (Dalbergia sissoo)
• Teak (Tectona grandis)
• White cedar (Dysoxylum malabaricum)
• White chuglam (Terminalia bialata sapwood)

2. Dimensions for Timber Units (Clause 5.1, Table 1)

Note: Tolerance on dimensions is -0 to +3 mm.

3. Additional Specifications

• Moisture content as per IS:287-1973.
• Seasoning as per IS:1141-1973.
• Preservation treatment as per IS:401-1982.
• Termite protection as per IS:6313 (Parts 1-3)-1981.

flowchart TD