Papan gipsum itu tidak kedap air.

Indonesian usually does not need a verb like is / am / are in simple descriptive sentences.

So:

• Papan gipsum itu = that gypsum board
• tidak kedap air = not waterproof / not water-tight

Put together, it naturally means:

• That gypsum board is not waterproof

This is very normal Indonesian. A word like adalah is generally not used for this kind of adjective phrase.

Itu usually means that.

In this sentence, papan gipsum itu means:

• that gypsum board
• or the gypsum board (depending on context)

In Indonesian, itu after a noun often works like a specifier. It can point to something already known in the conversation, so in real usage it may feel like English that or the.

Compare:

• papan gipsum = gypsum board / a gypsum board
• papan gipsum itu = that gypsum board / the gypsum board

In Indonesian, words like ini and itu normally come after the noun they modify.

So:

• papan gipsum itu = literally gypsum board that
• natural English: that gypsum board

This is one of the common word-order differences between Indonesian and English.

Examples:

• rumah itu = that house
• buku ini = this book
• mobil itu = that car

Use tidak to negate:

• verbs
• adjectives
• some stative expressions

Use bukan to negate:

• nouns
• pronouns
• noun phrases
• classifications/identifications

Here, kedap air functions like an adjectival expression meaning waterproof / water-tight, so tidak is correct:

• tidak kedap air = not waterproof

Compare:

• Papan gipsum itu tidak kuat. = That gypsum board is not strong.
• Itu bukan papan gipsum. = That is not gypsum board.

So the choice depends on what is being negated.

Kedap air means waterproof, water-tight, or impermeable to water, depending on context.

Breakdown:

• kedap = airtight / sealed / impermeable
• air = water

Together, kedap air literally means something like impermeable to water.

In everyday translation, waterproof is usually the most natural English choice.

Related expressions:

• kedap suara = soundproof
• kedap udara = airtight

It is a fixed expression made of two words, but it functions together like a single descriptive unit.

So in the sentence:

• tidak kedap air

the whole phrase means:

• not waterproof

You should learn kedap air as a set phrase, much like learning waterproof in English as one idea.

Papan means board or plank, and gipsum means gypsum.

So papan gipsum means:

• gypsum board
• plasterboard
• drywall (depending on region and context)

The exact English translation can vary:

• In American English, people often say drywall
• In British English, plasterboard is common
• Gypsum board is a more direct, technical translation

Yes. Although itu literally corresponds to that, in real Indonesian it often helps mark something as specific or already known.

So depending on context, papan gipsum itu could be understood as:

• that gypsum board
• the gypsum board

For example, if you are already discussing one particular board in a room, itu may feel closer to English the.

A simple approximate pronunciation is:

• PAH-pan GIP-soom EE-too TEE-dahk KAY-dahp AH-eer

A few notes:

• papan = PAH-pan
• gipsum = GIP-soom
• itu = EE-too
• tidak = often TEE-dahk; in casual speech the final k may be very unreleased or soft
• kedap = KAY-dahp
• air = usually pronounced like ah-EER or AH-eer, not like English air

Indonesian pronunciation is generally quite regular compared with English.

Yes, depending on context.

Kedap air strongly suggests waterproof or water-tight, but in practical translation people may choose:

• not waterproof
• not water-resistant
• not impervious to water

If the context is construction materials, the intended meaning is often that the material does not fully block water and should not be assumed safe in wet conditions.

So not waterproof is usually the clearest everyday translation, but context can shift the nuance slightly.

You would replace itu with ini:

• Papan gipsum ini tidak kedap air.

That means:

• This gypsum board is not waterproof.

So:

• ini = this
• itu = that

And both come after the noun:

• papan gipsum ini
• papan gipsum itu

Yes, it is natural and grammatical.

Its structure is very typical:

• noun phrase: Papan gipsum itu
• negation: tidak
• description: kedap air

So it follows a common Indonesian pattern:

• [thing] + [not] + [adjective/description]

For example:

• Rumah itu tidak besar. = That house is not big.
• Tas ini tidak mahal. = This bag is not expensive.
• Papan gipsum itu tidak kedap air. = That gypsum board is not waterproof.