Learn Hardcore Indonesian: Di ruang tamu ada rak buku dan karpet tipis di atas ubin. - In the living room there is a bookshelf and a thin carpet on top of the tiles.

Di ruang tamu = in the living room.
Di atas is a compound preposition meaning on top of/over. So di atas ubin = on the tiles. Using di twice is normal because each phrase marks a different location: the overall place (living room) and the surface (tiles).

Can I start with Ada instead: Ada rak buku dan karpet tipis di ruang tamu?

Yes. Both orders are correct:

Di ruang tamu ada … highlights the place first (topic: the living room).
Ada … di ruang tamu presents the existence first. Meaning is the same; it’s just a difference in emphasis.

Do I need words for “a/the” before rak buku and karpet?

Indonesian has no articles. Bare nouns can be indefinite or definite from context. To make it explicit:

Indefinite: sebuah rak buku, sebuah karpet tipis.
Definite: add itu/ini (that/this), e.g., rak buku itu, karpet tipis itu.

How do I make it plural (e.g., “bookshelves,” “rugs”)?

Use quantifiers or context; Indonesian doesn’t require a plural ending.

Quantifiers: beberapa rak buku, dua rak buku, banyak karpet.
Reduplication: rak-rak buku, karpet-karpet (possible but less common in everyday speech for inanimates; quantifiers are more natural).

What’s the difference between rak buku, lemari buku, and lemari?

Rak buku: open book shelves/rack.
Lemari buku: book cabinet, often with doors/glass.
Lemari: cabinet/wardrobe in general (could be for clothes, dishes, etc.).

What does ruang tamu literally mean, and how is it different from ruang keluarga and kamar tamu?

Ruang tamu: literally “guest room,” but it means the living room/reception area.
Ruang keluarga: family room/den.
Kamar tamu: guest bedroom. Don’t say kamar tamu if you mean living room.

Is di atas one word, and how is it different from the prefix di-?

Di atas is two words (preposition + noun). Writing diatas as one word here is incorrect.
Di- (with a hyphen) is a passive prefix attached to verbs, e.g., ditulis, dimakan. Different function and spelling.

Does di atas mean “on (touching)” or “above (not touching)”?

Context decides. Often it implies contact (like a rug on tiles). It can also mean “above” without contact, but you’d usually make that clear from context or add clarification.

Is di atas ubin necessary? Carpets are obviously on the floor.

Not necessary. You could say Di ruang tamu ada karpet tipis. Di atas ubin adds the detail that the floor surface is tiled. Alternatives: di lantai (on the floor), di lantai ubin (on the tiled floor).

What is ubin, and how is it different from lantai, tegel, or keramik?

Ubin: tile (individual floor tile).
Lantai: floor (the surface in general).
Tegel: older/loan word for tile; still understood.
Keramik: ceramic; lantai keramik means a ceramic-tiled floor.

What does ada do here? Can I use punya or memiliki instead?

Ada states existence/presence: there is/are.
You can rephrase with possession:

Informal: Ruang tamu ini punya rak buku dan karpet tipis.
Formal: Ruang tamu ini memiliki sebuah rak buku dan karpet tipis. For describing where things are, ada … di … is the most natural.

Can I use terdapat instead of ada?

Yes. It’s more formal/literary: Di ruang tamu terdapat rak buku dan karpet tipis.

Is the adjective order right in karpet tipis? Where do adjectives go?

Yes. Adjectives typically follow the noun: karpet tipis (a thin rug).
Intensifiers go before the adjective: karpet sangat tipis, karpet cukup tipis.

How do I negate the sentence?

Use tidak ada:

Di ruang tamu tidak ada rak buku dan tidak ada karpet tipis. You can also say: Di ruang tamu tidak ada rak buku maupun karpet tipis.

How do I make it definite: “the bookcase and the rug are in the living room”?

Commonly: Rak buku dan karpet itu ada di ruang tamu.
If you worry only the rug sounds definite, repeat itu or clarify: Rak buku itu dan karpet itu ada di ruang tamu or Keduanya ada di ruang tamu.

Do I need to repeat di before each location phrase?

Each phrase takes its own di as needed. In the original, di ruang tamu sets the general location; di atas ubin specifically modifies karpet tipis. Repeating di is normal and not redundant.

Is ruangan tamu acceptable?

The set phrase is ruang tamu. Ruangan means “room/space” generically, but ruangan tamu is not the standard collocation for living room.

Any register or word-choice notes for karpet, permadani, and keset?

Karpet: general rug/carpet (neutral).
Permadani: ornate/fancy carpet (Persian-style; more formal/literary).
Keset: doormat.

What classifiers can I use for quantity with these nouns?

Very common/neutral: sebuah rak buku, sebuah karpet.
For flat/fabric-like items: sehelai or selembar karpet can also work.
Numbers: satu/dua/… rak buku, dua karpet tipis.

Does di atas ubin apply only to the rug, or also to the bookcase?

Grammatically it most naturally attaches to karpet tipis (the nearer noun). If you want it to apply to both, rephrase for clarity, e.g., Di ruang tamu ada rak buku dan karpet tipis; keduanya di atas ubin, or describe the floor: Lantainya ubin.