🇱🇰 Sri Lanka · Standards & approvals · Updated 2026
Wind loading & roofs in Sri Lanka
Roofs in Sri Lanka are conventionally pitched at 25° with a 450 mm overhang, in a high wind band. That means strengthened fixings and roof tie-downs are required — the roof must be strapped down to the structure, not just rested on it.
Wind loading & roofs is one of the requirements that decides what your building actually has to be — and therefore what it costs. This page sets it out for Sri Lanka specifically, from that country's own construction conventions and site conditions, with the practical sequence to follow and the cost consequences spelled out.
Requirements in Sri Lanka
| Requirement | Value | Why it matters |
|---|---|---|
| Wind band | high | Uplift, not weight, governs the roof. Wind lifts roofs off buildings far more often than it pushes them over. |
| Roof pitch | 25° | Converts plan area to real surface at a factor of about 1.10, and interacts with wind uplift — very low pitches suffer higher uplift. |
| Eaves overhang | 450 mm | Shades walls and throws rainwater clear of the foundation. |
| Tie-downs | Required | Straps carrying uplift from rafter through wall plate into the wall, and in cyclonic areas continuously to the foundation. |
| Impact glazing | Not required | Standard glazing is adequate for the design wind speed. |
| Rainwater goods | Sized to local rainfall | Gutter and downpipe sizing should follow local rainfall intensity, not habit. Undersized gutters overflow into the wall head. |
What to do, in order
- 01Establish the design wind speed
It comes from the national wind map and your site's terrain category. Exposed and coastal sites carry substantially higher loads than sheltered suburban ones a few kilometres away.
- 02Design the load path for uplift
Covering to purlin, purlin to rafter, rafter to wall plate, wall plate to wall, wall to foundation. The roof fails at whichever link is weakest.
- 03Specify the fixing schedule
Use the prescribed schedule for the wind band. Fixing spacing is the whole design — it is not a place to economise.
- 04Detail the edges
Ridges, eaves and verges see the highest local pressures. Most roof failures start at an edge, not in the middle.
- 05Size the drainage
At 25° the roof sheds fast. Gutters, downpipes and the ground-level disposal must take the peak intensity, not the average.
What it does to the cost
- —Roofing is typically 12–16% of construction cost on a single-storey house — the third largest element after substructure and walling.
- —Tie-downs, strengthened fixings and (in cyclonic zones) impact glazing add materially to both the roof and the envelope. They are code items, not optional upgrades.
- —Measuring roof area as plan area under-measures by 10–30% depending on pitch — the most common single costing error there is.
Price the building these rules describe
Upload your drawings and get an itemised bill of quantities in LKR (₨), measured to the SLS 573 standard Sri Lanka professionals use.
Generate my Sri Lanka BoQWind loading & roofs in Sri Lanka — frequently asked
What are the wind and roofing requirements in Sri Lanka?
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Roofs in Sri Lanka are conventionally pitched at 25° with a 450 mm overhang, in a high wind band. That means strengthened fixings and roof tie-downs are required — the roof must be strapped down to the structure, not just rested on it.
Wind band in Sri Lanka — what is it?
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high. Uplift, not weight, governs the roof. Wind lifts roofs off buildings far more often than it pushes them over.
How does this affect what the building costs?
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Roofing is typically 12–16% of construction cost on a single-storey house — the third largest element after substructure and walling. Tie-downs, strengthened fixings and (in cyclonic zones) impact glazing add materially to both the roof and the envelope. They are code items, not optional upgrades. Measuring roof area as plan area under-measures by 10–30% depending on pitch — the most common single costing error there is.
What is the first thing I should do?
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Establish the design wind speed: It comes from the national wind map and your site's terrain category. Exposed and coastal sites carry substantially higher loads than sheltered suburban ones a few kilometres away.
Is this legal or code advice?
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No. These are conventional practice and planning allowances, compiled so a cost estimate is realistic rather than confidently wrong. The building authority in your municipality, and a professional registered in Sri Lanka, are the only authorities on what your project must comply with.