Building Works · 20 August 2026

Wet Weather on a Landed Build in Singapore: What Actually Stops

Every landed programme we have ever been shown by an owner has one thing in common. Somewhere in it is a bar chart that assumes it does not rain.

Singapore has no dry season. There are two monsoon surges and an inter-monsoon period of afternoon thunderstorms, and between them they produce a lot of days on which some part of a building site cannot work. A programme that makes no allowance for that is not optimistic — it is simply wrong, and the argument about whose fault the slippage is arrives about four months in.

What follows is what genuinely stops when it rains, what does not, and the two clauses in your contract that decide who carries the cost when it does.

What actually stops

Rain does not halt a site. It halts specific activities, and which ones they are is the whole point — because a well-sequenced job can carry on through weather that flattens a badly sequenced one.

Concrete pours

A pour caught by heavy rain part-way through is the expensive one. Surface water works into the top of the fresh concrete, and what you are left with is a weak, dusty layer exactly where you least want it. Once that happens the remedy is to cut it out and make good, which costs more than losing the day would have.

So pours are called on the forecast rather than on the sky. Cancelling a pour means standing down a pump, a supply of ready-mix and a full gang, and rebooking them — which is why a run of unsettled weather costs more days than the number it actually rained on.

Excavation and anything in an open hole

Singapore's residual soils turn to slurry quickly. An open excavation takes water in from the surface and from the ground, the base becomes unworkable, the sides soften, and plant loses traction on the access route. Then the water has to be pumped out and disposed of properly rather than pushed into the road drain, which takes its own time.

Deep work near a boundary is the version to watch, because a softened excavation is not just a delay — it is a risk to the neighbour's ground. We wrote separately about excavation on landed sites.

Anything that needs a dry substrate or a dry cure

External plaster and skim coat, external painting, and — the important one — applied waterproofing. A membrane put down on a damp substrate, or rained on before it has cured, does not fail loudly. It fails in about three years, from inside a completed house, which is the most expensive way for it to fail. This is why we will stand a waterproofing gang down rather than push on, and it is the same failure mechanism described in where waterproofing actually fails on landed homes.

Lifting, and work at height, in a storm

Lightning stops work outright, and it is not negotiable. Craneage, scaffolding, roof work and steel erection all come down when a warning is active, and the stoppage lasts until it is safe rather than until it stops being inconvenient. On a build with a lot of structural steel this is a real programme item, not a footnote.

What does not stop

Once a structure is topped out and made watertight, most of the remaining value is internal: M&E first fix, internal blockwork and plaster, screeds, tiling, carpentry, second fix. None of that cares about the weather.

That is the single most useful thing to understand about wet-weather planning, because it converts a weather problem into a sequencing decision. A programme that gets the roof and the external envelope closed before the wetter months has somewhere to put its labour when it rains. A programme that leaves the house open while chasing an earlier finish on paper has nowhere to go, and it is the one that loses whole weeks.

Ask your builder where the labour goes on a wet day. If the honest answer is "home", the programme has a hole in it.

The A&A version, which is worse

On a new build an open structure is a nuisance. On an A&A or a partial reconstruction, the open structure is attached to a house that still has finishes, still has services, and quite often still has an owner's belongings in it.

Taking a roof off, opening up a floor, or removing part of an external wall creates a period during which the existing house is only as dry as the temporary protection over it. Temporary protection is not a roof. Wind takes sheeting off; a surge finds the one lap that was not tied down; and the water that gets in does not stay where it landed — it runs along a ceiling and comes out somewhere with a finish on it.

Three things reduce this to a manageable risk. Plan the open period to be as short as the structure allows and treat it as a critical activity rather than a gap. Specify the temporary protection properly and inspect it, rather than assuming. And move what matters out of the affected part of the house first, because arguing afterwards about a damaged floor is a poor substitute for it not being there.

Silt, runoff and the complaint that arrives from outside

Heavy rain on a site with exposed earth produces silty water, and silty water leaving the site and reaching a public drain or the road is an enforcement matter, not a housekeeping one. It is also the thing your neighbours will photograph.

Earth control measures — perimeter drains, silt traps, a wash bay for wheels leaving the site, covering stockpiles — exist for this and belong on site before the wet weather, not after the first complaint. When an owner asks why the preliminaries line on a quotation is not smaller, some of the answer is here.

Who carries the delay: the two clauses that decide it

This is the part worth reading before signing rather than during an argument.

Extension of time. Most building contracts allow the contractor additional time for exceptionally inclement weather. Two things about that are worth understanding. First, "exceptionally" is doing a lot of work in that sentence — ordinary rain in a country with two monsoons is not exceptional, and the contract usually defines a threshold rather than leaving it to opinion. Second, an extension of time is normally time and not money: the contractor is relieved of liability for lateness, but is not necessarily paid for the extra weeks. Read your own contract, because the wording varies and the difference between "time only" and "time and cost" is the whole of the argument.

How weather is evidenced. A claim for weather days is worth exactly as much as the record behind it. That record is the site diary and, where the contract requires it, rainfall data. If nobody is keeping a daily record of what was stopped and for how long, the claim becomes a memory contest six months later.

So: agree at the outset who keeps the diary, that it records the activity stopped rather than just "rain", and that it is issued to you regularly rather than produced at the end. The same principle applies to milestone billing — the record has to exist while the events are happening.

What to ask before you sign

How many wet-weather days are allowed for in this programme? A specific number is a sign someone has thought about it. Zero is a sign the completion date is decoration.
What is planned for wet days? There should be an answer involving internal work, not an empty site.
When does the envelope close? The date the structure becomes watertight is the most important date on a landed programme and it is rarely the one owners are shown.
On an A&A, how long is the house open, and what protects it? Get this described, not assumed.
What does the contract say about inclement weather — time only, or time and cost? And what evidence does it require?
Who keeps the site diary and will I see it?

The short version

Rain does not stop a site; it stops pours, excavation, anything needing a dry substrate, and all lifting during lightning. Everything internal carries on, which makes wet weather a sequencing question rather than a weather question — the programme that closes the envelope early has somewhere to put its people, and the one that does not loses weeks. On an A&A the exposure is worse because the house being protected is still yours and still furnished. And when time is lost, what decides who carries it is the extension-of-time wording and whether anyone was keeping a daily record at the time. Both of those are settled before the first day on site, or not at all.

Planning a landed build or A&A and want the programme to survive the weather?

We build landed A&A and reconstruction work in Singapore as a BCA General Builder Class 2 (GB2) contractor. Tell us what you are planning and when you want to start, and we will tell you where the weather risk actually sits in that sequence — including when moving a start date by a few weeks is worth more than anything else you could do. Message us on WhatsApp, or see A&A works and in-house metal fabrication.

Common questions

How many wet-weather days should a landed programme allow for?

There is no single correct number, and any builder quoting one without reference to your sequence is guessing. What matters is that the programme allows for some, and that the allowance is stated rather than hidden. A programme showing zero weather days on a project spanning a monsoon period is not an aggressive programme, it is an inaccurate one, and the completion date it produces will not survive contact with the site.

Does rain always delay the whole project?

No, and this is the most useful thing to understand. Once the structure is topped out and the envelope is watertight, the remaining work is largely internal — services, plaster, screeds, tiling, carpentry — and none of it is weather-dependent. The projects that lose whole weeks to rain are the ones still open to the sky. That makes the date the envelope closes one of the most important dates on the programme.

We are doing an A&A and the roof has to come off. What are we exposed to?

For the duration of that opening, the existing house is only as dry as the temporary protection over it, and temporary protection is not a roof. Wind lifts sheeting and a heavy surge finds any lap that was not properly secured, and water that gets in travels along ceilings before it appears. Keep the open period as short as the structure allows and treat it as a critical activity, specify and inspect the protection rather than assuming it, and move anything that matters out of that part of the house first.

If the build is late because of rain, do we pay for the extra weeks?

That depends entirely on your contract. Most forms allow the contractor an extension of time for exceptionally inclement weather, which relieves them of liability for lateness. Whether they are also paid for the prolongation is a separate question, and the wording differs between contracts. Read the clause before signing, and note that "exceptionally" is usually tied to a defined threshold rather than left to opinion.

Why does the builder need a site diary?

Because a weather claim is worth as much as the record behind it and no more. A diary that records which activity was stopped and for how long, kept daily while it is happening, is evidence. A recollection assembled six months later during a dispute is not. Agree at the outset who keeps it, that it records the stopped activity rather than just noting rain, and that it is issued to you regularly rather than produced at the end.