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Question DetailsAsked on 12/7/2016

I have wet spots on my wall downstairs wall only. No plumbing is in this exterior wall. Who can diagnose?

There are also no windows near these spots, upstairs or down stairs. Only appeared after bad rain and wind. Hasn't gotten worse since and the outside doesn't seem to have damage or anything. Sides of house are plastic.

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Answered 3 years ago by Member Services


You said it - blowing / heavy rain - probably either because of no or blocked gutters/downspouts, or just rain blowing against the house, saturated the soil right against the foundation and it found a void or crack in the foundation or in the waterproof sealant on the outside of it - or maybe even overtopped the foundation and came in through the bottom of the first story wall. Most commonly, if significant breakthrough it means it ponded against the foundation, but just saturating the soil can sometimes cause damp spots without significant actual free water pooling in the basement/ground floor.

Of course, it is possible it came in through the siding, but without doors or windows nearby (usually entry points) unless there is visible siding damage or gaps, pretty unlikely to be from that.

Since this evidently is not a recurring event, I will assume it is not due to generally high groundwater or elevated groundwater due to continued heavy rain over an extended period - which would have caused continued wetness for days or weeks, not just a one-time damp spot.

If wet spot is coming up through the floor or at the slab/foundation interface and the slab is damp, could be the water table rose in the heavy rain. IF higher up on the wall, then almost certainly due to water seeping dowen along the foundation and coming in through a void in the wall.

Simplest solution: make sure the gutters and downspouts are directing roof runoff (the biggest source of water getting near the foundation unless you are subject to surface flooding or high groundwater) well away from the house - 3 or more feet in generally "tight" or fine-grained clayey or silty soils, or more like 6-10 feet in coarser, free-draining soils. Generally, if your lawn is mushy after a rain you have tight soil, if you can walk around on it in street shoes (no raised edge on sole) just minutes after a good rainfall stops without getting wet feet, and you do not have ponding in the yard for more than minutes after the rain stops, you have free-draining soil. Also - if ground is generally muddy after a rain, probably tight soil.

Then check along the house and be sure the ground surface slopes away from the house for at least that above distance from the house, at least at a 2% slope 1/4" drop per foot of run) and preferably more like 8-10% (about 1 inch per foot) for at least the first couple of feet away from the foundation. If you have bare ground around the house, then in free-draining soils you can cover that with compacted clayey soil (about 1 inch thick) or with outdoor "permanent" plastic pond liner (about $0.30-0.50/SF) sloping correctly away from the house, which can be covered with bark or stone or other architectural covering such as you desire for appearance sake. If you have plantings or lawn close to the house then takes a lot of work to take that up in areas where the water is ponding buy the foundation, and with "bush" plantings the plastic liner has to be raised where the plant roots go through it so that is not a drain hole for the runoff back to the foundation. Deep rooted trees and shrubs and individual plants like that are not recommended close to foundations anyway because the roots tend to break them up - better to use shallow-rooted planter beds with annuals or bulb perennials or groundcovers.

Concrete or asphalt around the house, sloping away from it, can also work extremely well if desired architecturally - but need good bitumastic or flashing sealing at the foundation and water seals cast into the expansion joints in concrete to really stop concentrated infiltration at the joints. Asphalt works well if kept sealed at any cracks. Of course, it has to slope away from house 2% or more - which makes for uncomfortable walking if used as a path, so this is not the normal solution.

Generally, if you get proper slope on the ground around the house AND have gutters and downspouts leading the roof runoff well away, you will be protected against water coming through the foundation - or over the slab for slab-on-grade houses. Of course, if you are subject to surface runoff from the yard or neighboring areas coming up to your foundation, then generally berming or swale construction at least 6-10 feet from the house to keep it from getting near the foundation is the best solution.

Note in doing sloping, there should be 4-6 inches of exposed foundation below the siding to reduce the risk of insect infestations (they commonly will not climb more than a few inches on bare concrete or cinderblock). In serious ant country no height protects because they are climbing toward the smells from the house, not just randomnm exploring, so periodic treatment around the foundation with poison or diatamaceous earth is best. Subterranean termite country generally recommneded to have 8-12 inches of exposed concrete wall below the siding.

Last resort, though does not sound like needed for your apparently sporadic wetting, sometimes with very porous soil or if in a low-lying area or in high groundwater area, a french drain outside the foundation is needed to intercept and carry the infiltrated water away. Also, in chronic or seasonal high groundwater cases, underdrains under the basement slab and sump pump are commonly needed - but again, does not sound like the case for you.

You can find a LOT more commentary in the previous questions on this issue in the Home > Basement Waterproofing link in Browse Projects, at lower left.

For major waterproofing of the foundation Basement Waterproofing is your normal Search the List category - but bear in mind even with a minor case that could be solved by outdoor regrading, many of those contractors will advise a very expensive drain or exterior lining system or both, so try the prevention of ponding or water by the foundation and draining it away first - go to deliberate buried drains or waterproofing only if surface water control will not handle it.

In your case sounds like you need (if you cannot DIY) probably just a Gutter Cleaner (if gutters overflowed) or Gutter contractor or Handyman if gutters are leaking. Gutters would be the Search the List category if you have no gutters and roof runoff is falling right by and able to pool at the foundation (need for gutters becomes more definite if roof overhang is less than about 3 feet or ground slopes toward the foundation). For ground resloping or putting in a clay or plastic cutoff layer Landscaping would be the normal Search the List category.

Note - if you put in a liner material (impervious compacted soil or plastic ) this does not mean you cannot have plantings near the foundation - though best not to have deep-rooted ones there anyway. It is common to put in plastic liner with sliced-open raised "dimples" or mounds for plants like rose bushes and such to go through (to keep the bulk of the runoff water out) though watering those plants so their roots get wet but not the foundation is tough- usually requires a timed weep hose. Overlying a liner with a few inches to foot or so of planterbed material is common as well, using plants whose roots do not go deeper than to the liner - as long as both the liner and the ground surface slope away from the house properly, and as long as gardening does not dig into the liner. Decorative stones or bark or such oer a liner material is fine too, as long as it is free-draining and the liner slopes away to ensure any water coming down through the decorative material drains away from the foundation well.

Generally, for your type case, once you have ruled out infiltration through the siding, the fix for a single damp spot is generally quite simple and normally a minor DIY job - except if you need gutters and do not have them that is not an easy DIY job if you want metal gutters, though RainGo or similar plastic ones are quite easy to DIY if you don't mind ladder work and have decent roof height.

Of course, you need to dry out the damp spot in the house well to prevent the mildew/mold growth that will commonly start in a couple of days if left wet. Simple dehumidifier and/or ventilation with a strong fan blowing on it commonly works for bare surfaces - finished walls you commonly have to open up the wall to dry it out - though generally small openings near the floor with a small fan directed right into it, then a foot or so opening at the top for exhaust works well, as of course do the professional ducted blowers (rentable) that blow into the wall through a 2-3 inch opening with an opening provided near the top for venting, or better yet pull air through the wall and exhaust it outside to get the humid air out of the area. Each damp stud bay needs to be dried out individually if doing it this way - don't count on drying openings just every 4-6 feet reaching all parts of the wall in a reasonable (couple of day) time.

Answered 3 years ago by LCD

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