Капитальный ремонт уже начался.

In Russian, ремонт is very often used as a singular mass/collective noun. So капитальный ремонт is a standard expression meaning something like:

• major repairs
• a major renovation
• an overhaul

Even though English may prefer a plural noun like repairs, Russian naturally uses the singular ремонт.

Капитальный ремонт is a set phrase. It usually means a major repair job, complete renovation, or overhaul, not just a small fix.

Compare:

• ремонт = repair, renovation
• капитальный ремонт = major renovation / full-scale repair / overhaul
• косметический ремонт = cosmetic renovation, superficial redecoration

So капитальный here does not literally mean capital in the English sense. In this phrase, it means something more like thorough, major, or fundamental.

Because the verb here is начаться = to begin / to start.

• начать = to start something
• начаться = to begin, to start

So:

• Он начал ремонт. = He started the renovation.
• Ремонт начался. = The renovation started / began.

In your sentence, ремонт is the thing that began, so Russian uses начаться, not начать.

The -ся marks the verb as reflexive, but in many cases like this it is better understood as part of the dictionary form rather than literally meaning it started itself.

Here:

• начать = to start something
• начаться = to start, to begin

So -ся often helps make the verb intransitive. In this sentence, it shows that ремонт is not the object being started by someone else in the grammar of the sentence; instead, it is the subject of beginning.

In the past tense, Russian verbs agree with the subject in gender and number.

The subject is ремонт, which is:

• masculine
• singular

So the past tense form is:

• начался = masculine singular

Compare:

• ремонт начался = the renovation began
• работа началась = the work began (работа is feminine)
• занятия начались = the classes began (занятия is plural)

Уже means already, and its position is quite natural here.

Капитальный ремонт уже начался is the neutral word order:
The major renovation has already started.

Russian word order is flexible, so you may also hear:

• Уже начался капитальный ремонт.
• Капитальный ремонт начался уже. — possible, but less neutral in many contexts

Placing уже before the verb is a very common way to say that the action has already happened.

Начался is perfective.

Dictionary forms:

• начинаться = to be beginning / to begin repeatedly / to start unfolding
• начаться = to begin, to start

The perfective is used because the sentence presents the beginning as a completed event: the renovation has already begun.

If you used the imperfective, it would usually sound different in meaning or context:

• ремонт начинался = the renovation was beginning / used to begin

That is not what this sentence is expressing. Here the point is that the starting point has already been reached.

Russian does not form the present perfect the way English does.

English says:

• has started
• has already begun

Russian usually just uses the past tense, often with a word like уже if needed:

• уже начался

So начался can correspond to English started, has started, or began, depending on context.

Yes. That is a very natural translation.

Depending on context, капитальный ремонт may be translated as:

• major renovation
• major repairs
• overhaul

And уже начался can be:

• has already started
• has already begun
• already started

So The major renovation has already begun is an excellent translation.

It is in the nominative case, because it is the subject of the sentence.

• ремонт = nominative singular
• капитальный agrees with it, so it is also nominative singular masculine

The subject is the thing that began:

• Капитальный ремонт = the major renovation
• уже начался = has already begun

The main stresses are:

• капита́льный
• ремо́нт
• уже́
• начался́

A rough pronunciation guide:

kapi-TAL-nyy re-MONT oo-ZHE na-chal-SYA

A more careful note:

• льн in капита́льный can be tricky for English speakers
• ё does not appear here; it is ремо́нт, not рёмонт
• the stress in начался́ is on the last syllable

Yes, Russian word order is flexible, but different orders can sound more or less natural depending on emphasis.

Neutral:

• Капитальный ремонт уже начался.

Other possible orders:

• Уже начался капитальный ремонт.
  This can sound like you are presenting the event itself first: The major renovation has already started.

• Капитальный ремонт начался уже.
  Possible, but often more marked, and it may sound like already is being emphasized in contrast with some expectation.

For learners, the original order is the safest and most neutral.

Yes, very common. You will often see it in everyday life, building management, public notices, and official language.

For example, it is commonly used when talking about:

• apartment buildings
• roads
• schools
• plumbing or infrastructure
• long-term building maintenance

So this is a useful real-world phrase, not an unusual textbook expression.