LESLIE: Tom in Tennessee is on the line and needs some help with a porch. Tell us what you’re working on.
TOM IN TENNESSEE: Well, I just bought the house maybe two months ago. It has a screened-in back porch with different, various sizes of stone. I’m not sure exactly what it is but it has cement in between them.
TOM: Yep.
TOM IN TENNESSEE: And it’s a smooth porch. And when it rains or when the humidity is high, we have a layer of water on the porch. And I know the roof is not leaking, because we have a table and chairs and they’re not wet. And I don’t understand where that water could be coming from.
TOM: Well, if it’s not because of gravity – so if it’s not falling – that means it’s being drawn up into the slab from somewhere underneath that. So, that usually means that there’s water collecting somewhere around that perimeter of that porch area. And it’s saturating that concrete and that stone and it’s sucking it right up and condensing on the surface.
TOM IN TENNESSEE: Yeah, that sounds possible.
TOM: So, then, what you do for that is you try to identify the source of the moisture. It could be grading and gutters, it could be soil that’s sloping into the wall, not sloping away enough. And you try to dry that up as much as possible.
I suspect it’s going to change. Right now, it’s not that hot; it’s fairly damp, a lot of rain. We’re getting into the warmer summer months, so it’s not something you’re going to see every day. But I could understand that in certain periods of the year, with a certain amount of precipitation, that this would be common if that rainwater is not properly managed.
TOM IN TENNESSEE: OK. OK. I don’t think it’s the downspouts, because I’ve checked those. And the only possibility could be the drainage on the outside of the porch.
TOM: Mm-hmm. How far away from the wall are the downspouts extended?
TOM IN TENNESSEE: Well, there’s actually one at the corner of the screened-in porch but there’s no water at that corner. The water is mainly in the middle of the porch itself.
TOM: Well, see, here’s the thing about water: it’s not always logical. You can have it – you can have a malfunctioning downspout or water that’s piling towards one corner and then have it show up 10 feet away, 20 feet away. I’ve seen that happen on a frighteningly regular basis because that’s the water behaves. I would tell you this: make sure the downspouts are at least 6 feet from the house. Don’t let them come out 1 or 2 feet, like most of them do. Get that water well away, even if you have to just throw some extensions – some leader extensions – on those spouts for a few weeks to see if it has an effect. Just get that water away from those corners and regrade it so it slopes away and then let’s see what happens.
TOM IN TENNESSEE: OK. OK. That makes sense. Thank you.
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