Wij hebben de plank opgehangen zonder dat we nieuwe spijkers hoefden te kopen.

Because ophangen is a separable verb in Dutch.

• Base verb: ophangen = to hang up
• It is made of:
  • op = up
  • hangen = hang

In the perfect tense, separable verbs usually split like this:

• Wij hebben de plank opgehangen.

So the prefix op gets attached to the past participle gehangen, giving opgehangen.

If you used only gehangen, it would mean just hung, not specifically hung up.

This is the perfect tense in Dutch, used here to describe a completed action.

The pattern is:

• hebben/zijn + past participle

Here:

• wij hebben opgehangen = we have hung up / we hung up

The verb ophangen takes hebben, not zijn, because it is normally used as a transitive verb here: something is being hung up, namely de plank.

De plank means the shelf/board/plank, so it refers to a specific one.

• de plank = the shelf / the plank
• een plank = a shelf / a plank

A learner may also wonder why it is de rather than het. That is simply because plank is a de-word in Dutch:

• de plank
• de planken

You just have to learn the noun with its article.

Zonder dat means without ... followed by a clause, often something like without the fact that or more naturally in English without doing / without having to do.

In this sentence:

• zonder dat we nieuwe spijkers hoefden te kopen

literally means something like:

• without that we needed to buy new nails

Natural English would be:

• without needing to buy new nails

The dat is there because zonder dat introduces a subordinate clause.

A useful comparison:

• zonder nieuwe spijkers te kopen = without buying new nails
• zonder dat we nieuwe spijkers hoefden te kopen = without us needing to buy new nails

The version with zonder dat is a bit fuller and explicitly includes the subject we.

Because after zonder dat, you get a subordinate clause, and Dutch subordinate clauses usually push the verbs toward the end.

Main clause:

• Wij hebben de plank opgehangen

Subordinate clause:

• zonder dat we nieuwe spijkers hoefden te kopen

Inside that subordinate clause:

• we = subject
• nieuwe spijkers = object
• hoefden te kopen = verbal part at the end

This is very normal Dutch word order. English keeps the verb earlier, but Dutch often saves it for later in subordinate clauses.

Hoefden is the past tense plural of hoeven.

Hoeven often means:

• to need to
• to have to

especially in contexts that are negative, conditional, or limiting.

So:

• we hoefden te kopen = we needed to buy
• but in this full sentence:
  • zonder dat we ... hoefden te kopen
  • = without needing to buy ...

Forms of hoeven:

• ik hoefde
• jij hoefde / hoefde jij
• wij hoefden

So hoefden agrees with we.

Because hoeven is followed by a te-infinitive.

So the pattern is:

• hoeven te + infinitive

Examples:

• Ik hoef niet te werken. = I do not need to work.
• We hoefden geen nieuwe spijkers te kopen. = We did not need to buy new nails.

That is why you get:

• hoefden te kopen

Not all Dutch verbs take te, but hoeven does.

Because nieuwe spijkers is the object of kopen, and in Dutch subordinate clauses the object often comes before the final verb cluster.

So the structure is:

• we = subject
• nieuwe spijkers = object
• hoefden te kopen = verbs

This may feel unusual to an English speaker, because English would say:

• we needed to buy new nails

But Dutch commonly says:

• we nieuwe spijkers hoefden te kopen

with the object before the verbs at the end.

Because spijkers means nails, and in this context Dutch naturally uses the plural to mean some nails in general.

• een spijker = a nail
• spijkers = nails

Using the plural sounds natural if you would normally need more than one nail for the task. Even if English also uses the plural here, it is still worth noticing that Dutch does the same.

Both wij and we mean we.

• wij is the full, stressed form
• we is the unstressed, very common spoken/written form

So:

• Wij hebben ...
• we ... hoefden ...

is completely normal.

A learner may expect one form to be used throughout, but Dutch often mixes them naturally. If you want, you could also say:

• We hebben de plank opgehangen zonder dat we nieuwe spijkers hoefden te kopen.

That would sound very natural too.

Yes. A shorter and very natural alternative is:

• Wij hebben de plank opgehangen zonder nieuwe spijkers te hoeven kopen.

This avoids zonder dat and uses an infinitive structure instead.

Both versions are correct, but there is a small difference in style:

• zonder dat we nieuwe spijkers hoefden te kopen
  more explicit, full clause
• zonder nieuwe spijkers te hoeven kopen
  more compact

For learners, the original sentence is useful because it clearly shows the subordinate clause structure.

It can depend on context.

Plank can mean:

• a plank
• a board
• a shelf

In a sentence about hanging it up, English might translate it as shelf if that fits the situation better. Dutch plank is broader than English plank in some contexts.

So if the meaning shown to the learner is shelf, that is perfectly possible. If the context is more literal, plank or board may also fit.

Because the sentence is not saying we didn’t buy new nails. It is saying we did not need to buy new nails.

That is an important difference:

• we kochten geen nieuwe spijkers = we did not buy new nails
• we hoefden geen nieuwe spijkers te kopen = we did not need to buy new nails

The actual sentence expresses lack of necessity, not simply whether the buying happened.

That is why hoefden te kopen is used.