Health wise you can but don't stay too long. But if he wants you to stay out until he's done fixing it. THen you stay out.

Wear a mask or a damp handkerchief over your mouth so you don't breath in the molds. You should be alright. I don't know how your uncle will be treating the mold but though I should say that contrary to popular thought, bleach does NOT kill mold. It does remove the visible stains but it doesn't kill it under the surface. To get rid of mold, what you do fist is kill it, then clean it with bleach and then cover it back over after making sure you won't have a moisture problem again. If you just cover it over and haven't addressed where the moisture is coming from, it will happen again and again. Here is a great formula for killing mold spores. 1/2 gal. white vinegar 1/2 gal. hydrogen peroxide-common peroxide available from your drugstore 1 cup boric acid keep closed tightly mix well - use in a spray bottle on a dry surface. Shake well and spray area well. The vinegar/peroxide kills active live mold and the boric acid keeps them that way. (Note: uncapped peroxide loses it's oxygen molecules to the air when not capped tight and becomes H2O [water], so keep this solution in a bottle that can be capped off tight). Boric acid works on mold bodies like it does on roach bodies - cuts them and they bleed to death because they cannot "coagulate". This solution will not "bleach" out the mold stain. After mold is under control, then you can bring out the bleach and whiten the mold stains.