Base­ment floors re­quire prepa­ra­tion prior to floor­ing in­stall

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

QI like your col­umn in the Free Press, and I have a ques­tion for you. We have re­moved our car­pet­ing from our base­ment and now are con­sid­er­ing what we should put in place of the car­pet. We would like to put in lam­i­nate floor­ing, but peo­ple have told us this is not a good idea de­pend­ing on mois­ture and that car­pet tiles would be bet­ter. I’m con­fused. Is it OK to in­stall lam­i­nate floor­ing? Thank you, Shirley Trafton An­swer: In­stalling floor­ing on a con­crete base­ment floor is of­ten prob­lem­atic, even in a dry base­ment. Con­den­sa­tion is al­ways a con­sid­er­a­tion be­cause the floor may be con­sid­er­ably cooler than the other base­ment sur­faces, and spe­cial mea­sures may have to be taken to pre­vent this from oc­cur­ring. Lam­i­nate floor­ing may be a good choice, but should have sub­floor pro­tec­tion to pre­vent dam­age from mois­ture. Be­cause the con­crete slab in a base­ment floor is in con­tact with the soil be­neath and touch­ing the foun­da­tion walls at the perime­ter, it may be con­sid­er­ably cooler than the air and sur­round­ing sur­faces in the same area. If the rel­a­tive hu­mid­ity (RH) is too high in the base­ment and air move­ment is stag­nant, there is a high prob­a­bil­ity of con­den­sa­tion on the cool base­ment slab. If there is no floor cov­er­ing on this slab, a small amount of con­den­sa­tion should even­tu­ally dry with­out any se­ri­ous con­se­quences. Some white, pow­dery ef­flo­res­cence may be left be­hind, but there should be lit­tle chance of any ma­jor mould growth or dam­age hap­pen­ing, if the damp sur­face is al­lowed to dry unim­peded. As soon as the con­crete is cov­ered, whether it is with floor­ing, stor­age boxes, suit­cases, or other items, prob­lems can oc­cur. The main con­sid­er­a­tions for choos­ing your base­ment floor­ing is it does not in­crease the chance of con­den­sa­tion and will not al­low mould growth if that does oc­cur. Car­pets, whether they are made from syn­thetic fi­bres or nat­u­ral ones, are not the best op­tion. Even ny­lon or polyester car­pets can ab­sorb some mois­ture de­pend­ing on the tex­ture and can be dif­fi­cult to clean. Not only can they trap mois­ture against the cool con­crete, they may also be a great col­lec­tor of dirt and dust. If this de­bris gets wet while em­bed­ded in the car­pet fi­bres, mould growth is likely. This may only be no­ticed as a damp, musty smell in the base­ment, but should be avoided, none­the­less. Car­pet tiles of­ten have foam back­ing that may pre­vent the ac­tual fi­bres from touch­ing the con­crete sur­face, pre­vent­ing wet­ting, but this can pose an­other dilemma. The foam back­ing can also act as in­su­la­tion, pre­vent­ing warm air from the heat­ing sys­tem con­tact­ing the con­crete sur­face. This can make the con­crete tem­per­a­ture slightly colder than when un­cov­ered, fur­ther in­creas­ing the chance of con­den­sa­tion. To make mat­ters worse, the foam back­ing can also act as a par­tial vapour bar­rier, trap­ping mois­ture un­der­neath. For th­ese rea­sons, I al­ways rec­om­mend re­moval of any ex­ist­ing car­pets from the base­ment to my clients and avoid­ing re­place­ment di­rectly on the con­crete floor. Lam­i­nate floor­ing is nor­mally com­prised of medium to high den­sity wood fi­bre with a mois­tur­ere­sis­tant and scratch-re­sis­tant sur­face. The prob­lem with in­stalling this ma­te­rial in any lo­ca­tion is it is not very mois­ture re­sis­tant on the un­der­side. Also, wa­ter spilled or sit­ting on the sur­face for more than a short pe­riod of time will leak into the seams be­tween the in­di­vid­ual planks. Ei­ther of th­ese wa­ter-re­lated is­sues can cause the floor­ing to swell, ren­der­ing it use­less. To pre­vent the un­der­side from ab­sorb­ing mois­ture from the sub­strate or sub­floor below, a thin foam un­der­lay is nor­mally in­stalled, which also gives the floor a more cush­ioned feel­ing when walked on. The foam un­der­lay may be highly mois­ture re­sis­tant, which nor­mally will in­hibit wa­ter vapour from trav­el­ling from the sub­strate to the fi­bre­board core of the lam­i­nate floor­ing. The down­side of this same prop­erty is con­den­sa­tion oc­cur­ring on the sur­face of the cool con­crete slab may not be able to eas­ily dry for long pe­ri­ods of time. In that case, mould may be­gin to grow on dust, dirt and de­bris un­der­neath the foam un­der­lay­ment. If it re­mains wet, it will fur­ther the spread of the mould un­til the floor­ing is re­moved. Even worse, if a wet­ting does oc­cur be­cause of foun­da­tion seep­age, the wa­ter trapped un­der the floor­ing may have dis­as­trous con­se­quences, ul­ti­mately re­quir­ing the re­moval and dis­card­ing of the lam­i­nate floor­ing. The so­lu­tion to this prob­lem may be to in­stall an un­der­lay that not only is mois­ture re­sis­tant, but also has a mech­a­nism to al­low wa­ter vapour to es­cape in case of mi­nor seep­age or con­den­sa­tion. There are sev­eral sub­floor prod­ucts that in­cor­po­rate a ply­wood or OSB sheath­ing sur­face with a plas­tic or foam base and are mod­er­ately priced. The best ones have a par­tially raised or dim­pled bot­tom layer that al­lows some air­flow un­der­neath to help dry­ing. Once th­ese prod­ucts are in­stalled, there is lit­tle chance of mois­ture ab­sorp­tion from ei­ther lam­i­nate or car­pet be­cause they are no longer in con­tact with the cool sur­face of the con­crete floor. Even if con­den­sa­tion does hap­pen, it should be lim­ited to the small air space un­der the sub­floor­ing, which should even­tu­ally dry if the sub­floor is prop­erly in­stalled and vented. If the base­ment is known to have pe­ri­odic seep­age, the sub­floor may be ef­fec­tive, or a more com­plex sub­floor ven­ti­la­tion sys­tem may be re­quired. No mat­ter what type of floor­ing is cho­sen for your base­ment, it should be in­stalled with preven­tion of con­den­sa­tion from the cool con­crete floor taken into con­sid­er­a­tion. The best method to en­sure this is to in­stall a sub­floor with a vented airspace be­neath, to pre­vent di­rect con­tact be­tween the floor­ing and the sub­strate. Ari Marantz is the owner of Trained Eye Home In­spec­tion Ltd. and the past pres­i­dent of the Cana­dian As­so­ci­a­tion of Home & Prop­erty In­spec­tors — Man­i­toba (cahpi.mb.ca). Ques­tions can be emailed to the ad­dress below. Ari can be reached at 204-291-5358, or check

out his web­site at trained­eye.ca.

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