The Shulchan Arukh (OC 632:1) rules that invalid sekhakh at the edge of a sukkah does not invalidate the sukkah if it is less than four amoth, based on the principle of dofen akuma. He also rules that one can fulfill one's obligation of sitting in a sukkah while sitting under sekhakh that is invalid for less than four tefachim. Assuming a dofen akuma is more than four tefachim but less than four amoth, can one fulfill one's obligation by sitting partially/entirely under the innermost less-than-four tefachim (adjacent the valid sekhakh), or is that considered an invalid combining of lenient halachoth l'moshe misinai?

  • I don't understand the question. Once it's wider than four tefachim how can you sit under it? Commented Oct 2, 2017 at 9:27
  • 1
    @DannySchoemann Because the last 3.5 are Lavud to the Sekhach. It's only the initial 3.8 Ammah which are a Dofen. You are allowed 4 Tefachim next to the Dofen that you can sit under. Why does it matter if the Dofen is vertical or horizontal?
    – Double AA
    Commented Oct 2, 2017 at 13:15

1 Answer 1


Shulchan Aruch Orach Chaim 632,1 says one can sit under invalid schach in the middle of the schach, but one cannot sit under invalid schach on the side of the schach next to the wall: .

סְכָךְ פָּסוּל, פּוֹסֵל בָּאֶמְצַע בְּד' טְפָחִים; אֲבָל פָּחוֹת מִד', כְּשֵׁרָה, וּמֻתָּר לִישַׁן תַּחְתָּיו מִן הַצַּד אֵינוֹ פּוֹסֵל אֶלָּא בְּד' אַמּוֹת, אֲבָל פָּחוֹת מִד' אַמּוֹת, כְּשֵׁרָה דְּאָמְרִינָן דֹּפֶן עֲקֻמָּה, דְּהַיְנוּ לוֹמַר שֶׁאָנוּ רוֹאִים כְּאִלּוּ הַכֹּתֶל נֶעֱקָם וְיֵחָשֵׁב זֶה הַסְכָךְ הַפָּסוּל מִגּוּף הַכֹּתֶל, וְדָבָר זֶה הֲלָכָה לְמֹשֶׁה מִסִינַי. הִילְכָּךְ בַּיִת שֶׁנִּפְחַת בָּאֶמְצַע וְסִכֵּךְ בִּמְקוֹם הַפְּחָת וְנִשְׁאַר מִן הַתִּקְרָה סָבִיב בֵּין סְכָךְ כָּשֵׁר לַכְּתָלִים פָּחוֹת מֵאַרְבַּע אַמּוֹת, כְּשֵׁרָה, וּמִיהוּ אֵין יְשֵׁנִים תַּחְתָּיו כָּל זְמַן שֶׁיֵּשׁ בּוֹ אַרְבָּעָה טְפָחִים

Sechach posul (invalid) is only permitted in the centre of the Succah when surrounded by kosher Sechach up to less than 4 tephachim (hand-breaths), when less then 4 tephachim one can sleep underneath the sechach pasul it (the Mishna brura says many poskim disagree and its better to not sleep underneath unless less than 3 tefachim יש פוסקים שסוברין דאף דפחות מד"ט הסוכה כשרה מ"מ תחת אותו המקום אסור לישן ולאכול אא"כ אותו המקום הוא פחות מג"ט לכן יש להחמיר לכתחלה). On the side, if 1 of the 3 essential walls is 4 amos (24 tefachim) the sechach is pasul but less than 4 amos (24 tefachim) the sechach is kosher because Dofen Akuma (the wall bends) so this possul sechach on the side is considered like the wall a law from Moses at Sinai. Therefore an opened roof of a house that sechach was placed in the middle and there is some roof material unfit sechach on the sides less than 4 amos (24 tefachim), the succah is Kosher, but you cannot sleep underneath the unfit sechach at all when 4 tefachim or wider

If there is 4 tefachim or a larger distance from Sechach till the wall the Mishna Brura explains:

ר"ל דאף דהסוכה כולה כשרה היא מ"מ אותו המקום כיון שהוא ד"ט הוא מקום חשוב לעצמו ואין מתבטל לגבי הסוכה
i.e 4 tefachim or more is Choshuv (Like a Resus Hayochid to itself) and cannot be considered part of the Succah, therefore one cannot move himself under there and he should only stay under the Sechach Kosher*.

Conclusion: You cannot sleep under the 3.9 amos even though we say Dofen Akuma on the walls that sides the sechach if it is 4 tefachim or larger.

*Note:as long as most of his body, his entire head and some of his table are under the sechach kosher in-case he leans over out of the kosher sechach,this from Succah 3a אמר רב שמואל בר יצחק הלכה צריכה שתהא מחזקת ראשו ורובו ושולחנו And is brought down in S.A O.C 634,1.

  • @loewian is this the answer you are looking for
    – user15464
    Commented Sep 26, 2018 at 16:54

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