Drain wa­ter out of new base­ment now

Winnipeg Free Press - Section G - - HOMES - ARI MARANTZ

QUES­TION: I en­joy read­ing your col­umn ev­ery week for the prac­ti­cal ad­vice you have. I am hop­ing for some ad­vice on a new condo that I re­cently pur­chased that is cur­rently in con­struc­tion.

It is a town­house-style condo that is two sto­ries, plus a base­ment. From the very be­gin­ning, the base­ment floor has been cov­ered in what looks like at least a foot of wa­ter. I was told by the real es­tate agent that is sell­ing these units for the builder that it will even­tu­ally be pumped out and the base­ment floor poured. I re­cently vis­ited the condo again and it now is at the stage where the elec­tri­cal and plumb­ing are done and the dry­wall is up. How­ever, there is still the same amount of wa­ter in the base­ment.

Is that nor­mal pro­to­col? I am not concerned about the wa­ter as long it is re­moved and a proper floor poured, but is there a con­cern about mould form­ing in the walls and floors with so much hu­mid­ity from the stag­nant wa­ter in the house sit­ting in the base­ment all the time?

Thanks for any ad­vice you might have on this.

AN­SWER: I thought your ques­tion would be a good one to an­swer af­ter the re­cent heavy rains that have flooded dozens of base­ments in our area. While

Su­san Tsang, Win­nipeg the sit­u­a­tion may be dif­fer­ent in your condo un­der con­struc­tion, the sources of the wa­ter may be the sim­i­lar and the out­comes have the same con­cerns.

There are two main is­sues with the large amount of wa­ter sit­ting in the un­fin­ished base­ment in your condo. Firstly, the ques­tion of­ten arises in this sit­u­a­tion of the ef­fects of the high mois­ture con­tent of the soil un­der­neath the newly poured base­ment-floor slab.

I have heard builders and oth­ers tell cus­tomers that hav­ing the wa­ter in there is a good thing. The the­ory pre­sented is that the soil is sat­u­rated and at its max­i­mum den­sity, so that when it dries out it will shrink and pre­vent the typ­i­cal floor slab heav­ing and crack­ing seen in many new homes.

Un­for­tu­nately, this is not true and ex­ces­sive mois­ture may in­crease the risk of crack­ing and heav­ing in the floor slab. Be­cause the soil in this area is sat­u­rated, it will shrink ex­ces­sively as it dries, which will in­crease the chance of fur­ther ex­pan­sion when re­soaked. If the soil is damp, but not com­pletely sat­u­rated, be­fore pour­ing of the slab it will min­i­mize the large swings in shrink­age and ex­pan­sion and pre­vent dam­age to the slab.

The next con­cern is the one that you have iden­ti­fied in your ques­tion. Hav­ing the dry­wall com­plete in the home with a small lake in the base­ment will in­crease the chance of mould growth due to high hu­mid­ity. This will be com­pounded once the dry­wall is taped and painted, which adds con­sid­er­ably more mois­ture to the home as these ma­te­ri­als dry.

Nor­mal build­ing ma­te­ri­als will re­lease a sig­nif­i­cant amount of wa­ter vapour into the en­vi­ron­ment of a new home, but this will be pre­vented from dry­ing due to the ad­di­tional mois­ture in the base­ment. Once the wa­ter is fi­nally pumped out and the foun­da­tion in­su­lated and cov­ered with a plas­tic air/vapour bar­rier, mois­ture will be trapped in this wall cav­ity and may have dif­fi­culty es­cap­ing. This will be ac­com­pa­nied by the mois­ture that evap­o­rates from the freshly poured con­crete. It is quite com­mon to see ar­eas of mould and mildew be­hind the fi­bre­glass in­su­la­tion in base­ments in new homes for this rea­son.

An­other is­sue that you have not in­quired about should also be ad­dressed. The plumb­ing drains and weep­ing tile pipes are in­stalled on top of or slightly embed­ded in the soil be­low the base­ment floor slab and they may be af­fected by the wa­ter. With that much wa­ter in the base­ment, it will be very dif­fi­cult to near-im­pos­si­ble for the plumber to in­stall the proper plumb­ing drains and con­nec­tions. The wa­ter will have to be re­moved, al­most com­pletely, be­fore this can be com­pleted. If the ground is swelled to its max­i­mum due to the stand­ing wa­ter, these pipes may shift sig­nif­i­cantly if in­stalled im­me­di­ately af­ter the wa­ter is re­moved. This may pre­vent them from hav­ing the ideal slope for proper drainage, which can cause the drains to be slug­gish.

It is likely that the wa­ter in the base­ment is pri­mar­ily com­ing from the weep­ing tiles, but they should be ter­mi­nat­ing in a sump pit so that the wa­ter can be pumped back out­side the house. Your builder may be re­luc­tant to in­stall the pit and pump be­fore the con­crete floor slab, for good rea­son. Be­cause of the high mois­ture con­tent of the soil, a newly in­stalled plas­tic sump pit may heave and pop right out of the ground if it does not have the weight of the con­crete floor slab and pea gravel on top to hold it down.

Re­gard­less, a tem­po­rary pump and pit could be eas­ily in­stalled to get rid of the ex­ces­sive mois­ture or the proper pit tem­po­rar­ily held in place with braces that are re­moved af­ter the floor is poured. Also, the drainage-tile pip­ing in­stalled un­der­neath the floor slab should be in­stalled with suf­fi­cient slope for drainage, which may be ad­versely af­fected if the soil heaves or shrinks too much.

To briefly sum­ma­rize, and an­swer your di­rect ques­tion, the wa­ter should be pumped out as soon as pos­si­ble to al­low rea­son­able dry­ing of the soil prior to com­ple­tion of the in­su­la­tion, dry­wall and floor slab. It doesn’t mat­ter whether this is done with a tem­po­rary pump or with a proper sump pump and pit but you should put pres­sure on the builder to do it now, ei­ther way.

Any de­lay in drain­ing your base­ment could re­sult in sky­rock­et­ings costs for re­pair.

Newspapers in English

Newspapers from Canada

© PressReader. All rights reserved.