For words ending in the -ing suffix, is the suffix stressed? Unstressed? Does adding the -ing suffix affect the stress of the other syllables?
Example: (u is untressed, ‘ is stressed)
Deteriorate is (U ‘ U U ‘), is deteriorating (U ‘ U U ‘ U)? Is it (U ‘ U U ‘ ‘)?
It’s common to distinguish primary stress from other kinds of stress in English. For example, the word deˈterioˌrate has primary stress on the second syllable but the word deˌterioˈration has primary stress on the penultimate syllable, and secondary stress on the second syllable. In some traditions, the final syllable of "deteriorate" is not considered to have even secondary stress (see my answer here about secondary stress and tertiary stress). So deteriorate can also be transcribed deˈteriorate.
The word deteriorating has no stress of any kind on the final syllable. I don’t recall hearing of any speakers who move the primary stress to the penultimate syllable. Its stress pattern would be transcribed as deˈterioˌrating or deˈteriorating (depending on how you transcribe the base form).
The addition of the inflectional suffix -ing is not expected to cause any kind of stress shift, but there might be a few possible exceptions.
Possible candidates for stress shift
I can only think of one marginal case where a word ending in -ing might have a different stress pattern from the corresponding unprefixed form.
In the base form inˈdwell, it seems to be usual to put the primary stress on the second syllable (possibly with secondary stress on the first). The form ˈinˌdwelling however often takes primary stress on the first syllable—at least, when used as an adjective or as a noun. I don’t know whether the verb indwelling tends to take the same stress as the base form.
In cases like these, the nouns/adjectives can be viewed as taking stress as a compound (as with the word ˈbabyˌsitting) while the base verbs can be viewed as taking stress as a prefixed form (as with the word inˈscribe).
"Verb-centred Compound Nouns in English and Bulgarian", by Мaria Kolarova (2015), mentions indwelling as an (allegedly archaic) example of a verb-centered compound noun (p. 174).
British English "ricochet"?
The OED entry for the verb ricochet implies that in British English, stress on the third syllable may be more common in inflected forms (ricocheted/ricochetted and ricocheting/ricochetting) than in the base form ricochet (transcribed as /ˈrɪkəʃeɪ/, /ˈrɪkəʃɛt/). I’m not sure what the basis for that statement is, though. It is definitely possible to stress the same syllable throughout the paradigm of the verb: what the OED says is that "In [inflected forms] the main stress often falls on the third syllable, as it does sometimes also in other forms."