Short answer
What does IS 2645 say about an integral waterproofing compound? IS 2645 is a test standard for compounds added to cement mortar and concrete. It tests water permeability, setting time and strength, and it caps the dose at 3 percent by weight of cement, as the maker recommends. It does not say where to use the compound, and it does not say it replaces a membrane. Ask the maker and your engineer about the dose and the use.
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A waterproofing compound that is mixed into the cement is called an integral compound. Sellers make many claims for these products, and a reader cannot easily tell which are tested. The Indian standard IS 2645 sets the tests a compound must pass. This page explains what the standard covers, the limits it sets, and what it leaves to the maker and the engineer. It gives no product names, no prices and no site dose.
What does IS 2645 cover?
IS 2645 covers integral waterproofing compounds for cement mortar and concrete (clause 1). It tests a compound by two methods:
- Permeability. Mortar specimens are made with and without the compound, and the water that passes through them is measured.
- Setting and strength. The compound is mixed with the same cement, and the setting time and the compressive strength of the mortar are compared with plain cement.
The standard is about lab-tested products. It is not a set of site instructions. The container must show the maker’s dosage and instructions for use, and the maximum chloride content (clause 6.1), but the standard does not say what those instructions should be.
What limits does the standard set?
| Requirement | What the standard says | Clause |
|---|---|---|
| Dose | The compound is used in the proportions the manufacturer recommends, not exceeding 3 percent by weight of cement. | Clause 1, Note 1 |
| Chloride | The chloride content, tested to IS 6925, is declared by the maker and is not to exceed 2.0 percent by mass of the product. | Clause 3.4 |
| Permeability | The permeability of a specimen with the recommended dose is less than half that of a plain specimen. | Clause 3.1 |
| Setting time | The initial set is not less than 30 minutes and the final set is not more than 600 minutes. The initial set is not reduced, nor the final set increased, by more than 25 percent of the plain-cement value. | Clause 3.2 |
| Strength | The 3-day and 7-day compressive strength of the mortar cubes with the compound is not less than the minimum for the grade of cement used, and not less than 90 percent of the strength of cubes made with the same cement and sand only. | Clause 3.3 (a) and (b) |
The 3 percent figure is a cap. It is not a dose. The dose on a bag or a data sheet comes from the maker, and it should be within the cap.
What does the standard not say?
IS 2645 does not say:
- Where the compound should be used: on a terrace, in plaster, in a bathroom or in the foundation.
- Whether the compound can replace a membrane or another waterproofing layer.
- How the compound is applied: mixed in the concrete, as a slurry, or as a coat.
For the terrace, the choice of method is covered in terrace leakage and waterproofing: methods, slope and ponding test. That page says a cement-based coat or integral compound suits a sound slab with hairline cracks that do not move, and that moving cracks need a flexible membrane.
For a damp-proof layer, see Damp-proof course (DPC): what it is and where it goes. Whether a coat can take the place of a DPC is a decision for the engineer.
What should I ask the maker and the engineer?
- What dose does the maker recommend, and is it within the 3 percent cap in IS 2645?
- Does the product data sheet say it meets IS 2645, and what chloride content is declared?
- Where does the maker say the product is used, and does that match the place where I want it?
- Does the engineer agree that the compound is the right layer for this part of the house?
A curing compound is a different product, used to keep fresh concrete moist. It does not do the same job. See curing compound for concrete: when it can replace water curing.
What mistakes should I avoid?
These are practice points, not code rules:
- Treating an integral compound as a complete replacement for a membrane on a terrace that carries water or moves.
- Adding more compound than the maker recommends, in the belief that more is safer.
- Buying a product because a seller says it “lasts for years”. IS 2645 gives no lifespan, and this page gives none.
- Skipping the slope and the outlets on a terrace because a compound has been used.
Frequently asked questions
Does IS 2645 tell me how much compound to use?
It caps the dose at 3 percent by weight of cement, and says the manufacturer’s recommendation applies within that cap. The actual dose comes from the maker’s data sheet and the engineer.
Is a compound that meets IS 2645 waterproof?
IS 2645 tests permeability against a plain specimen, and it requires the compound to bring the permeability to less than half that of the plain mortar. It does not say the finished wall or roof will stay dry. Workmanship, cracks and slope still matter.
Can I use it in plaster?
IS 2645 covers cement mortar and concrete, but it does not say where the compound should be used. Ask the maker and the engineer.
These answers are practice guidance, not code quotes.
This guide is general information. Read the disclaimer. Your engineer decides which layer suits your house.
Related guides
- Terrace leakage and waterproofing: methods, slope and ponding test
- Damp-proof course (DPC): what it is and where it goes
- Curing compound for concrete: when it can replace water curing
Sources
General information only. It is not a structural design or professional advice. Ask a licensed structural engineer or architect to check your plans and site.