I og med at kostnadsoverslaget er høyt, blir felleskostnadene høyere.

It means since, as, or because.

In this sentence, i og med at kostnadsoverslaget er høyt gives the reason for what follows: the cost estimate is high, so the shared costs will be higher.

A few notes:

• i og med at is a fixed expression.
• It often sounds a bit more formal or explanatory than plain fordi.
• In many contexts, fordi could also work:
  • Fordi kostnadsoverslaget er høyt, blir felleskostnadene høyere.

So the meaning is basically causal: because the cost estimate is high.

Norwegian very often makes compound nouns where English uses several separate words.

So:

• kostnad = cost
• overslag = estimate

Together:

• kostnadsoverslag = cost estimate

Then the ending -et makes it definite:

• et kostnadsoverslag = a cost estimate
• kostnadsoverslaget = the cost estimate

This kind of compounding is extremely common in Norwegian.

Because the sentence refers to the cost estimate, not just a cost estimate.

Compare:

• et kostnadsoverslag = a cost estimate
• kostnadsoverslaget = the cost estimate

In Norwegian, definiteness is often shown by adding an ending to the noun, instead of using a separate word like the.

So:

• overslag → indefinite
• overslaget → definite

That is why you see kostnadsoverslaget er høyt = the cost estimate is high.

Because kostnadsoverslaget is a neuter noun.

The base adjective is høy = high, but predicate adjectives must agree with the noun:

• common gender singular: høy
• neuter singular: høyt
• plural/definite contexts: often høye

Since:

• et overslag = a neuter noun

you get:

• kostnadsoverslaget er høyt

So the -t is there because the noun is neuter.

Because høyere is the comparative form of høy.

So:

• høy = high
• høyere = higher

The sentence is saying that the shared costs are not just high, but higher as a result of the high cost estimate.

This is similar to English:

• The estimate is high
• The shared costs become higher

So høyt and høyere are related, but they do different jobs:

• høyt = basic adjective agreeing with a neuter singular noun
• høyere = comparative form

It means the shared costs, the common expenses, or in housing contexts often the monthly common charges/shared building fees.

The word is built like this:

• felles = shared/common
• kostnader = costs/expenses

And with the definite ending:

• felleskostnader = shared costs
• felleskostnadene = the shared costs

In real-life Norwegian, this word is especially common in discussions about apartments, housing cooperatives, and monthly fees paid jointly by residents.

Because the sentence begins with a subordinate clause, and then the main clause follows normal Norwegian verb-second word order.

The structure is:

• I og med at kostnadsoverslaget er høyt, = subordinate clause first
• then the main clause starts
• in a main clause, the finite verb usually comes in second position

So you get:

• I og med at kostnadsoverslaget er høyt, blir felleskostnadene høyere.

Not:

• I og med at kostnadsoverslaget er høyt, felleskostnadene blir høyere.

That second version sounds wrong in standard Norwegian.

You can compare:

• Felleskostnadene blir høyere.
• Derfor blir felleskostnadene høyere.
• I og med at kostnadsoverslaget er høyt, blir felleskostnadene høyere.

In all of these, the finite verb blir stays in second position in the main clause.

Because blir means becomes / gets / will be, while er means is / are.

So:

• felleskostnadene er høyere = the shared costs are higher
• felleskostnadene blir høyere = the shared costs become / will become higher

Here, blir suggests a result or change: because the estimate is high, the shared costs will end up higher.

In many practical contexts, this sounds more natural than er, because we are talking about an effect of the estimate.

Yes, in many situations you could.

For example:

• Fordi kostnadsoverslaget er høyt, blir felleskostnadene høyere.

That would mean almost the same thing.

However, there can be a slight nuance:

• fordi = straightforward because
• i og med at = since / given that / in view of the fact that

So i og med at can sound a little more formal, explanatory, or like the speaker is presenting a reason that is already accepted or obvious in the context.

Yes. A very natural alternative is:

• Felleskostnadene blir høyere i og med at kostnadsoverslaget er høyt.

This puts the main statement first and the reason after it.

Both versions are correct:

• I og med at kostnadsoverslaget er høyt, blir felleskostnadene høyere.
• Felleskostnadene blir høyere i og med at kostnadsoverslaget er høyt.

The difference is mainly one of emphasis:

• reason first → stronger focus on the cause
• result first → stronger focus on the outcome

It sounds fairly natural, but a bit more formal or written than very casual everyday speech.

Reasons:

• i og med at is a slightly more formal connector than fordi
• words like kostnadsoverslaget and felleskostnadene are typical of administrative, financial, or housing-related language

A more everyday version might be:

• Siden kostnadsoverslaget er høyt, blir felleskostnadene høyere.
• Fordi kostnadsoverslaget er høyt, blir felleskostnadene høyere.

So the original sentence is perfectly normal Norwegian, especially in written or semi-formal contexts.