Wet base­ment? Don’t blame neigh­bour’s reno

Winnipeg Free Press - Section G - - HOMES - MIKE HOLMES

ROB from On­tario asks in an email if a neigh­bour’s ren­o­va­tion could give him wa­ter prob­lems in his base­ment. Rob’s neigh­bour, whose house backs onto his in an or­di­nary sub­di­vi­sion, put an ad­di­tion on his home. Ever since it was com­pleted, there has been wa­ter in Rob’s base­ment af­ter heavy rain, and es­pe­cially dur­ing spring thaw.

The short an­swer is: Yes, it’s pos­si­ble, depend­ing on how the neigh­bour might have changed the grade dur­ing his ren­o­va­tion.

Tech­ni­cally, in most sit­u­a­tions, you aren’t al­lowed to change the grade of your lot dur­ing a ren­o­va­tion. When you ap­ply for a build­ing per­mit, you need to in­di­cate the grade slop­ing away from the house. But a full site-plan ap­proval — where a change in grade would be marked and could be ver­i­fied — is usu­ally only re­quired for new con­struc­tion. A build­ing in­spec­tor might no­tice dur­ing one of the site vis­its, but odds are, the fo­cus is go­ing to be on the con­struc­tion, so these things might slip by.

Even a sub­tle change in grade can af­fect how sur­face runoff will flow. If your neigh­bour ex­ca­vated for a base­ment or crawl space un­der the ad­di­tion, it’s in­evitable the grade would be al­tered — even if it were put back to, more or less, where it was. The fact that their lot has now got more cov­er­age than it did be­fore means there is less area for wa­ter to per­co­late back down un­der the sur­face. It’s got to go some­where — and, in Rob’s sit­u­a­tion, maybe it’s find­ing its way over to his prop­erty.

Now, I don’t rec­om­mend ac­cus­ing your neigh­bour if you start to find wa­ter in your base­ment. It might just be a mat­ter of a crack hav­ing de­vel­oped in your foun­da­tion some­where. That def­i­nitely does hap­pen over time, or as a re­sult of poor work­man­ship when the foun­da­tion was poured.

Odds are, the prob­lem is on your side. Could your down­spouts be emp­ty­ing too close to your foun­da­tion? Are the eave­stroughs filled with leaves and de­bris, so they spill over when it rains — right along­side your house? Have you changed your drive­way or pa­tio? That could eas­ily ex­plain the change in drainage and ac­count for wa­ter find­ing its way into your base­ment.

Are your down­spouts con­nected to weep­ing tile at your foot­ings in­stead of emp­ty­ing on the sur­face? Is your weep­ing tile bro­ken or clogged with tree roots? Do you have a sump pump, and does it dis­charge right out­side the wall of your house? If so, find a way to chan­nel that wa­ter away from your foun­da­tion wall or it will just find its way back in.

Or maybe you done some land­scap­ing, say, put in gar­den beds next to your house? That usu­ally causes some prob­lems. When you dig near the foun­da­tion walls — ei­ther to pull out old shrubs or to plant new — you are dis­turb­ing the soil there. It’s left less com­pressed and with more air pock­ets in it — air pock­ets that eas­ily let wa­ter flow through, al­low­ing it to get in next to your base­ment walls.

That wa­ter might come from your ir­ri­ga­tion sys­tem in the sum­mer months, or from snowmelt or heavy rain. The prob­lem isn’t caused by the wa­ter; it’s caused by the fact that the soil is dis­turbed and al­lows wa­ter in.

Wa­ter will al­ways fol­low the path of least re­sis­tance, and it al­ways flows down­hill.

An ob­vi­ous clue to check for if you sus­pect the prob­lem starts on your neigh­bour’s side is down­spouts di­rect­ing wa­ter onto your prop­erty. That’s a def­i­nite no-no, and you should dis­cuss it with him or her. If the prob­lem is caused by a change in grade, then you need to redi­rect the wa­ter at the sur­face be­fore it makes its way to your house. Dig swales — ba­si­cally, grassy ditches — that will in­ter­cept the wa­ter flow and chan­nel it away so your base­ment stays dry.

— Postmedia News


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