Can I use a gerundive like I would use an adjective as in the following example? It sounds fine to me, but I am somewhat suspicious; my intuition has failed before.
Infans lavandus clamabat.
The child that was supposed to take bath cried.
Urbs nobis capienda militiam novam paraverat.
The city which we were supposed to capture had acquired a new army.
This kind of use would make perfect sense to me. Participles can be used this way — often, at least — and I do not see the gerundive as any less of an adjective than a participle. However, my grammar does not mention this kind of use.
My grammar (Tuomo Pekkanen's Ars grammatica) has a title "Gerundive as attribute", but in all examples of the section the gerundive is used together with a noun modified by it — semantically an object. These are his examples:
spes urbis capiendae (also gerund urbem capiendi is possible)
in libertatem defendendam
legibus scribendis (also gerund leges scribendo is possible)
libro legendo
