The resin smells while it works. Here is what causes it, how to air the room, and who should stay away.
📍 We serve KL, Selangor & Putrajaya.
PU injection does give off a chemical smell while the resin is being pumped and reacting, and the cleaning solvent a crew uses adds to it. The smell is strongest during the job, in the room being injected, and fades as the resin cures and the room is aired out. Polyurethanes are made from isocyanates, which are known sensitisers, so keep children, pets and anyone with asthma out of the room while the work is done, open windows and run a fan, and ask the contractor for the product's safety data sheet. Market rates for the work itself run RM80 – RM250 per point (indicative 2026, Klang Valley).
PU injection seals a leak by pumping liquid polyurethane resin into the crack or slab through small ports called packers. When the resin meets water in the concrete it reacts and foams, filling the leak path, then cures into a flexible seal. ClickBina's PU injection guide explains the chemistry in detail.
Three things produce the smell people notice. The first is the resin itself and its accelerator while they are liquid and reacting. The second is the solvent or flushing agent crews use to clean the pump, hoses and any drips. The third is not chemical at all: a ceiling that has been wet for months often smells musty, and that damp smell is easily blamed on the injection.
Polyurethanes are made from isocyanates. The reference entry on MDI, one of the common isocyanates, notes that it is an allergen and sensitiser. That is the reason for sensible precautions, not panic: the exposure risk is greatest for the people handling the liquid every day, and the occupants' job is simply to stay out of the way and keep the room aired.
A typical bathroom-ceiling job runs in a set order: the ceiling board is opened, holes are drilled at an angle into the slab, packers go in, resin is pumped until it shows at the next packer, then the packers come out and the holes are patched. The PU injection guide notes most single-ceiling jobs are done in two to four hours.
The smell rises during pumping and while any resin that seeped out is wiped up. Drilling makes concrete dust rather than a chemical smell, which is why a careful crew sheets off the area before it starts.
| Stage | What you notice | What to do |
|---|---|---|
| Drilling | Noise and fine concrete dust | Close doors to other rooms; cover furniture below |
| Pumping resin | The strongest chemical smell | Keep children, pets and anyone with asthma out; open windows |
| Cleaning pump and drips | Solvent smell | Keep the fan running; ask the crew to take used rags away |
| Packers out, holes patched | Smell fading | Leave windows open and the fan on for a while |
| Next day | Little or no chemical smell | A musty smell is usually the damp ceiling, not the resin |
| Smell still strong days later | Uncured or spilled resin somewhere | Ask the contractor to come back and check |
Ventilation does most of the work. Before the crew starts, open the bathroom window and any window in the room below, switch on the bathroom exhaust fan, and close internal doors so the smell does not drift into bedrooms. A standing fan pointed out of a window helps in rooms with no exhaust fan.
The value of moving air away from people is well documented. In a UK HSE case study, workers exposed to isocyanate fumes developed occupational asthma, and installing fume extraction dramatically reduced the levels. A home ceiling job is a far smaller exposure, but the principle is the same: move the air out, and keep people out of the room while the liquid is in use.
Everyone else can usually stay at home with the doors closed and windows open. If anyone feels unwell, move them to fresh air and seek medical advice.
Once the packers are out, the holes are patched, any spilled resin is cleaned off and the smell has faded with the windows open, the room can be used normally. The exact time depends on the product, so ask the crew what the safety data sheet and technical sheet say, and keep the room aired in the meantime.
The bathroom above, if that is where the water came from, can usually go back into use after the job so the seal can be checked. ClickBina's PU injection ceiling leak guide explains why the area is checked again once the bathroom is used normally.
Every resin product comes with a safety data sheet. It lists what is in the product, the hazards, the protective equipment the applicator should wear and how spills are cleaned up. It is a reasonable thing to ask for before the job, and a careful contractor will not mind.
Good practice is mostly common sense. The crew wears gloves and eye protection, sheets the floor and furniture below, pumps no more resin than the leak path takes, wipes up any resin that bleeds out before it cures on the tiles, and takes empty containers and solvent rags away rather than leaving them in your bin.
Cheap DIY injection kits avoid none of this and usually fail anyway: hand-gun pressure pushes resin only a little way into the crack. ClickBina's DIY vs contractor guide covers when a home repair makes sense and when it does not.
A chemical smell that is still strong several days later usually means resin has dripped onto something absorbent, such as a ceiling board or a cabinet top, and is curing slowly there. The fix is to find and remove it. A musty or sour smell is different: it points to a ceiling that is still wet or growing mould.
If the ceiling board stayed wet for a long time it may need replacing rather than drying. ClickBina's ceiling water stains guide explains how to tell an old stain from an active leak.
These are the market ranges ClickBina's PU injection cost guide publishes (indicative 2026, Klang Valley). Ventilation and clean-up are part of doing the job properly, not an extra.
| Work | Market rate | Typical use |
|---|---|---|
| PU injection, slab seepage and ceiling leaks | RM80 – RM250 per point | Homes, condos, dripping ceilings |
| PU grouting, tanks, lift pits, basements | RM120 – RM300 per point | Deeper structures, higher water pressure |
| Epoxy injection, structural cracks | RM150 – RM400 per point | Bonding cracked beams, columns, slabs |
| Standard bathroom ceiling at per-point rates | RM960 – RM2,000 | A typical count of points |
| Minimum charge, small job | RM500 – RM800 whole job | Most crews will not mobilise below this |
WhatsApp us your job details for a quote — we reply within the hour. A renovation site visit is free, and a repair inspection is RM180, deducted from the bill if you go ahead. We serve KL, Selangor & Putrajaya.
💬 WhatsApp for a quoteAsk for the point count, or a fixed price, in writing before drilling starts, and ask how the room will be ventilated and cleaned at the end.
ClickBina is an experienced KL & Selangor contractor for waterproofing and leak repairs. WhatsApp us your job details for a quote and tell us about anyone at home who should be kept away from the work. We reply within the hour, the price we agree is a flat price with no hidden charges, and a renovation site visit is free, and a repair inspection is RM180, deducted from the bill if you go ahead.
How we estimated prices: every RM figure on this page is quoted unchanged from ClickBina's PU injection cost guide, where they are published as indicative 2026 market rates for the Klang Valley. This page is general information, not medical advice.
WhatsApp us your job details for a quote — we reply within the hour. A renovation site visit is free, and a repair inspection is RM180, deducted from the bill if you go ahead. We serve KL, Selangor & Putrajaya.
💬 WhatsApp for a quoteTell us what you need — we reply within the hour.