Why isn't "read" spelled "reat"

Question

Why isn't read spelled reat?

I mean build, building, built -> read, reading, reat?

PS I have dyslexia and I'm not native in English.

Answer 1

Build and read are irregular verbs, so called because they don't follow the regular rules of English verb conjugation. While occasional groups of irregular verbs behave similarly (for example, bleed and breed resemble read, at least when spoken), a given irregular verb need not resemble any other.

You can find a list of irregular verbs with conjugations here.

Answer 2

The Oxford English Dictionary has some remarks directed to the use of past tense in the case of the verb 'read':

▪ III.read, v.
(riːd)
Pa. tense and pa. pple. read (red). Forms: inf. 1 rǽdan, (-on, ræddan, north. reda, reða), 3 ræden(n), raden, 2–4 reden, 5 redyn; (and pres.) 2, 4 rade, 3–6 rede, 5–6 reede, Sc. red, reid, 6 (8 Sc.) reed; (3) 6–7 reade, 6– read. (Also 3 sing. pres. 1 ræt, 2–4 ret, 3 red, 3–4 rat.) pa. tense 1 pl. reordun; 1 rǽdde, 3–4, 6 radde, (4 rade), 4, 6 rad, (4 rat); 1 pl. red(d)on, 3, 6 (9) redd, 4 redde, 4–6 rede, 4–6 (7–8) red, 7– read. pa. pple. 1 rǽden, 4 reddynn, 6 readen; 1 rǽded, 3–4 redd, 3–6 redde, (4 radde), 3–6 (7–8) red, 4 rede, 6 reed(e, 6– read; 1 ᵹeredd, 3 ired, 3–4 irad, 4 iredde, yrade, 4–5 iradde.
[Comm. Teut.: OE. rǽdan = OFris. rêda, OS. râdan (MLG. raden, MDu. and Du. raden), OHG. râtan (MHG. râten, G. raten, rathen), ON. ráða (Sw. råda, Da. raade), Goth. -rêdan:—OTeut. *ræ̂đan, prob. related to OIr. im-rádim to deliberate, consider, OSl. raditi to take thought, attend to, Skr. rādh- to succeed, accomplish, etc.
The Comm. Teut. verb belonged to the reduplicating ablaut-class, with pa. tense *rerōđ and pa. pple. *garæ̂đono-z, whence Goth. -rairôþ, *-rêdans, ON. réð, ráðinn, OHG. riat, girâtan (G. riet, geraten), OS. ried or rêd, *girâdan (Du. ried, geraden). The corresponding forms in OE. are reord and (ᵹe)rǽden, but these are found only in a few instances in Anglian texts, the usual conjugation being rǽdde, ᵹerǽd(e)d, on the analogy of weak verbs such as lǽdan: cf. MLG. radde, redde, Sw. rådde, and G. rathete (for usual riet), Da. raadede. The typical ME. forms are redde or radde in the pa. tense, and (i)red or (i)rad in the pa. pple.; in the later language (from the 17th c.) all tenses of the verb have the same spelling, read, though in pronunication the vowel of the preterite forms differs from that of the present and infinitive. Individual writers have from time to time denoted this by writing red or redd for the pa. tense and pa. pple., but the practice has never been widely adopted.
The original senses of the Teut. verb are those of taking or giving counsel, taking care or charge of a thing, having or exercising control over something, etc. These are also prominent in OE., and the sense of ‘advise’ still survives as an archaism, usually distinguished from the prevailing sense of the word by the retention of the older spelling rede. The sense of considering or explaining something obscure or mysterious is also common to the various languages, but the application of this to the interpretation of ordinary writing, and to the expression of this in speech, is confined to English and ON. (in the latter perhaps under Eng. influence).]

This, again, is more an explanation of 'what' happened to the past tense of the verb, rather than 'why' it happened. But perhaps it has some small merit as an explanation of 'how' it happened.

My own sense of it is that it is an example of the tendency of language towards economy, the effort to use (and understand) 'red' or 'redd' to denote the past tense or past participle was not repaid in significantly greater clarity about what was being written, even though it is a reflected in the different pronunciation of the past tense ('I once read', 'I will read'). Furthermore, the form 'red' and even more so 'redd' were already 'staked out' by other (completely different) meanings.

EL&U member 'medica' has largely addressed this in this question-answer: Why do we say and write "read" instead of "readed" for the past?.

Incidentally, 'builded' was once not uncommon (from the OED):

'c 1150 The Grave in Thorpe Analecta 142 Ðe wes bold ᵹebyld er þu iboren were.] c 1205 Lay. 2656 He wolde bulden twa burh. 1297 R. Glouc. 439 At Wyndelsore..þat noble stede ys, Þat he let bulde hym sulf. c 1400 Mandeville 98 [He] destroyed it [Jerico] and cursed it, and alle hem that bylled it aȝen. 1430 Lydg. Story of Thebes d j in Dom. Archit. III. 47 A porche bylte of square stons. 1480 Caxton Descr. Brit. 13 He bylded Caunterbury. 1526 Pilgr. Perf. (W. de W. 1531) 138 b, Jerico, Hay, and Gabaon, whiche y⊇ pagans buylded. 1541 in Turner Sel. Rec. Oxford 164 Standyngs now made and buyldyd or hereafter to be made and buyld for the said fayre. 1562 J. Heywood Prov. & Epigr. (1867) 168 Roome was not bylt on one day. 1601 Chester Love's Mart. cx. (1878) 27 At Mount Paladour he built his Tent. 1644 Evelyn Mem. (1857) I. 75 A castle builded on a very steep cliff. 1718 Lady M. W. Montague Lett. II. liii. 78 The houses are tolerably well built. 1794 S. Williams Vermont 138 When the Indian builded his house. 1861 F. Nightingale Nursing 18 Your house must be so built as that the outer air shall find its way..to every corner of it.'

The question of why we settled on certain forms of words is - as others have said - a slippery slope to madness. But what is apparent is that the extraordinary imprecision in spelling and pronunciation in former times created the opportunity for so much variation (random or otherwise) to come down to us today.