The FLOSS rule: the spelling, the word list, and the exceptions

Double f, l, s, or z at the end of a one-syllable word when the vowel is short. Reading Universe calls this the FLoSS(Z) rule, or the double-consonant spelling pattern, and uses puff, fill, mess, and buzz. Reach All Readers states the same three conditions: one syllable, a short vowel, and a final f, l, s, or z. The name FLOSS comes from f, l, and s. Z is the same pattern, so buzz belongs with them.

The doubled letters spell one sound. bell is /b/ /e/ /l/, not /b/ /e/ /l/ /l/.

Words that follow the rule

Ending	Words
ff	off, puff, huff, cuff, stuff
ll	bell, fill, hill, well, doll, tell
ss	miss, mess, less, fuss, pass, kiss
zz	buzz, fuzz, fizz

stuff, tell, less, pass, and kiss are still one syllable and short vowels. stuff is /st/ plus /u/ plus /f/. The blend at the start does not stop the doubling at the end, because the final sound is a single f. That is different from a blend at the end, which does not double. Reading Universe uses mask and shelf for that case: the final consonant is not doubled when more than one sound follows the vowel.

Exceptions a teacher will hit

The rule is consistent, and it still has a short exception list. Reading Universe groups them.

Words that fit the shape and do not double: if, bus, gas, us, pal, yes, this. Also chef, gal, and quiz on that list. Teach if, bus, yes, and this as heart words when they show up. Do not build a spelling lesson on chef or quiz in the first FLOSS week.

Words that look like they should double s, but s says /z/: has, is, was. was is not a short-a word either. All three are heart words.

Words that double a different consonant: add, egg, mitt, putt. Those are not FLOSS. Mention them so a child who writes egg does not think the FLOSS list was incomplete. They are a separate odd set.

Final blends do not double: mask, desk, shelf, milk. The last two letters are two sounds. See consonant blends.

all, as in ball, is doubled l, and the vowel is not a plain short a. That chunk is a glued sound, on glued sounds. You can spell ball with ll and still teach the vowel as its own unit.

FLOSS in decodable text

In a decodable sentence, every pattern word should be readable from patterns already taught. A FLOSS word is legal in that sentence only after the doubling has been taught. Before that, bell is a trap: the child sees four letters and taps four sounds.

When the pattern is taught, read the double as one sound.

• The bell is on the hill.
• I miss the doll.
• The puff is in the well.

Heart words in those lines, if you use them, are marked on purpose: the, is, I. is breaks the doubling and the s says /z/, so it is not a pattern word. A decodable page that hides is inside a FLOSS list teaches the wrong rule.

Spelling dictation uses the same test. Say hill. The child should write h-i-ll, not h-i-l, once the rule is in place. If the word is if or bus, say so: this one does not double.

Reading Universe places the rule after digraphs and blends on its continuum, and it says other programs use another order. Short vowels and closed syllables are the real prerequisite, not a calendar date. CVC words such as hat and bed come first, on CVC words.

How to teach it

Keep the lesson on one ending, then mix.

1. Say the rule in the child's words: one syllable, short vowel, one ending sound, so the letter doubles. puff, not puf.
2. Sort a handful of cards: off, puff, and cuff on one side; bus and if on the other. Say why the second pile does not double.
3. Dictate three pattern words and one heart word. hill, miss, buzz, and if. The child should pause on if.
4. Read a line. The bell is on the hill. Tap the double as one sound.
5. Next day, mix ff and ll. Add ss only when those two are stable. zz can wait until buzz is needed.

A child who writes bel for bell needs the sort again, not a longer word list. A child who doubles bus needs the exception pile, not another chant.

One limit: the rule is a spelling pattern for one syllable and a short vowel. It will not tell you how to spell a two-syllable word, and it will not repair was, is, or of. Teach the exceptions as themselves. Do not stretch the chant until it swallows them.

FLOSS words show up across the K-2 Decodable Books units, which give K-2 readers a decodable book for every phonics pattern, in teaching order. Print PDFs need a printer, paper, scissors, and a stapler.