Building during the monsoon in Nepal: what to do before, during and after the rains

Every year, from around June to September, the monsoon brings heavy rain to Kathmandu Valley and most of Nepal. Many families wonder whether they should stop construction for the season or push on.

The honest answer: the monsoon doesn’t have to stop your project, but it changes what you can do on site. With the right plan, a house can keep moving through the rains without risking quality.

In short: finish excavation and foundations before the rains, keep working under a completed slab during the monsoon, pour concrete only around the forecast, and save exterior plaster, painting and waterproofing for the dry months after.

Before the rains: get out of the ground

The most weather-sensitive work happens at and below ground level. If you can, plan your start date so these are done before the heavy rain arrives:

• Excavation and foundations. Open trenches fill with water, the sides can collapse, and wet soil loses strength. Pumping out pits and re-cleaning the bottom wastes days.
• Plinth and backfilling. Once the foundation is back-filled and the plinth beam is cast, the site is far less vulnerable to flooding.
• Site drainage. Dig temporary drains so rainwater flows away from the building, not into the foundations or a neighbour’s plot.
• Material storage. Build a raised, covered store for cement, and plan where steel, sand and aggregate will sit off the wet ground.

If your naksa pass is still in progress, this is another reason to start the permit early. A permit that comes through in May lets you get the foundations in before the rain. One that comes through in July often means waiting.

During the monsoon: work under cover

Once the first slab is cast, a lot of work can continue underneath it, protected from the rain:

• Brick or block masonry on the floors below the slab.
• Electrical conduits and plumbing inside walls and floors.
• Internal plaster in rooms that are covered and drying properly.
• Doors and window frames, if the openings are protected.

Structural work above, such as columns and the next slab, can also carry on, but it needs more care.

Pouring concrete in the rain

Rain on fresh concrete washes out the cement, weakens the surface and changes the water-cement ratio the engineer designed for. We manage this by:

• Planning pours around the forecast and starting early in the day, when monsoon rain is less likely in the valley.
• Keeping tarpaulins and plastic sheets ready on site before the pour begins, to cover the slab within minutes if a shower arrives.
• Never adding extra water to make wet concrete easier to work. It looks convenient but makes the concrete weaker.
• Stopping at a planned construction joint if heavy rain sets in, rather than finishing a pour badly.

The upside: the monsoon is actually good for curing. Concrete needs to stay moist for at least seven days to gain strength, and the humid weather helps, as long as the surface isn’t damaged by heavy rain in the first few hours.

Protecting materials

• Cement absorbs moisture and goes lumpy. Store bags on a raised platform, under cover, away from walls, and use the oldest stock first.
• Steel reinforcement should be kept off the ground on timber or blocks and covered, so it doesn’t rust badly before use.
• Sand and aggregate need covering and a firm base so they don’t wash away or mix with mud.
• Bricks should be stacked on dry ground. They can be wetted before laying, but shouldn’t sit in standing water.

Safety on a wet site

Rain makes sites more dangerous. Scaffolding, ladders and formwork get slippery, trenches can collapse, and wet electrical cables are a serious risk. We check scaffolding after heavy rain, keep temporary wiring off the ground and stop work in thunderstorms.

After the rains: finish the outside

Some jobs simply turn out better once the walls have dried, usually from October onwards:

• Exterior plaster and painting. Paint on damp walls peels and blisters, and plaster dries unevenly.
• Roof and terrace waterproofing. Membranes and coatings need a dry, clean surface to bond properly.
• External paving and landscaping, once the ground has firmed up.

The dry season after the monsoon is also the best time to look for leaks and damp patches. The rains will have shown you exactly where water gets in, so you can fix it before the final finishes go on.

A simple monsoon planning guide

Season	Best work to schedule	Avoid if possible
Before the monsoon (March–May)	Excavation, foundations, plinth, site drainage	Leaving open trenches into June
Monsoon (June–September)	Masonry, conduits, plumbing and internal plaster under cover; carefully planned slabs	Excavation, pouring concrete in heavy rain, exterior finishes
After the monsoon (October onwards)	Exterior plaster, painting, waterproofing, paving	Rushing finishes onto walls that are still damp

Planning a build this year?

Good timing can save weeks on a project. If you’re about to start, read our checklist of what to sort out before you build in Kathmandu, then get a free estimate. We’ll plan your schedule around the seasons from day one.