Siman 87
Presented here for study, not as a practical ruling. The Shulchan Aruch rules by Sephardi custom, the Rema's glosses by Ashkenazi custom, and the Kitzur follows Ashkenazi custom. For a practical question, ask your rabbi.
א אֵין לָאִישׁ חֲזָקָה בְּנִכְסֵי מְלוֹג שֶׁל אִשְׁתּוֹ שֶׁאֲכָלָם שְׁנֵי חֲזָקָה, אַף עַל פִּי שֶׁהִתְנָה עִמָּהּ שֶׁאֵין לוֹ פֵּרוֹת בִּנְכָסֶיהָ. וְכֵן אֵין לָאִשָּׁה חֲזָקָה בְּנִכְסֵי בַּעֲלָהּ, עַל יְדֵי שֶׁאֲכָלָתַם שְׁנֵי חֲזָקָה. הַגָּה: וְדַוְקָא בַּחֲזָקָה כָּזוֹ, אֲבָל בְּחֶזְקַת נְזִיקִין, כְּגוֹן פְּתִיחַת חַלּוֹנוֹת וְכַדּוֹמֶה לָזֶה, יֵשׁ לָאִישׁ חֲזָקָה בְּנִכְסֵי אִשְׁתּוֹ, וְהוּא הַדִּין לְאִשָּׁה עַל בַּעֲלָהּ (רַבֵּנוּ יְרוּחָם בְּמֵישָׁרִים נָתִיב כ"ג ח"ז). וְעַיֵּן בְּחשֶׁן הַמִּשְׁפָּט סִימָן קמ"ט:
1 A man does not have squatting rights in his wife's melog properties (a wife's property which is not listed in the ketuba; the husband has usufruct rights, yet is not responsible for the property. See siman 83:13) which he has used for the years of chazaka (if someone enjoys the usufruct of a property for 3 years without counterclaim from the original owner, he can claim that he purchased the land even if he is unable to produce the document of sale), even if she had previously made a condition that he would not receive the usufruct of her property. Similarly a woman does not have squatting rights on her husband's lands when she has taken the usufruct for the chazaka years. Rema: Specifically with this type of squatting, but with damage rights, e.g. opening windows [in a house] (without counterclaim) and similar instances, the husband does develop damage rights, and the law is similar with respect to the woman on her husband's property (Rabbenu Yerucham in Meisharim, path 23, section 7). And see Choshen Mishpat chapter 149.
ב מִי שֶׁהֶחֱזִיק בְּנִכְסֵי אֵשֶׁת אִישׁ, לֹא עָלְתָה לוֹ חֲזָקָה, אֶלָּא אִם כֵּן הֶחֱזִיק בָּהֶם שְׁלשָׁה שָׁנִים אַחַר מוֹת בַּעֲלָהּ. וְעַיֵּן בְּחשֶׁן הַמִּשְׁפָּט סִימָן קמ"ט:
2 Someone who holds possession of a married woman's property does not accrue squatting rights (see above) unless he maintained possession for three years after the death of her husband. Rema: See Choshen Mishpat chapter 149.