This past Succos, a porch collapsed with people in the succa. Bechasdei Hashem, no one got hurt, but it brings to mind an important point: Are porches strong enough for a large crowd; what are the limits of porches?
I have heard a few such stories in the past (there was once a Simchas Bais Hashoeva by a rav, and they sold the tape ‘SBH with succa fall!’). I also once heard about a porch collapsing with a kiddy pool on it, and the mother got quite an injury. I asked an expert that it seems surprising – because you can have a porch full of snow, and there’s no problem. He answered that this is disproportionate weight. Also, they checked the porch, and found that the board against the house had only two screws (thick bolts – bolting it onto the house); one at each end – it should really have had one every foot or so (the nails are just strong enough to hold on the board itself, but to hold on the whole porch, it needs thick bolts). I would imagine that frum builders take this into account – as any porch can be used for a gathering, so we Yidden need special construction!
I know a yid who made a bar mitzva in his succa, and he asked an expert to come and check it – as he was going to have a large crowd, and especially because there was going to be dancing. I was there, and could see the floor flexing a bit, but apparently that in itself is not a problem. (One should also check for rotted wood etc.) He said the expert told him to check afterwards also, to make sure nothing loosened.
It should also be noted that it makes no difference how high a porch is off the ground – even just a few feet can be a danger. Also, children or anyone should not be underneath – or right next to – a porch at such a time.
In the picture above, note how there is a bolt every foot – one up, one down.