What lurks be­neath can be most im­por­tant!

David Hay­ward, ATFA Tech­ni­cal Man­ager, stresses the im­por­tance of as­sess­ing what lies be­neath the tim­ber floor.

Australasian Timber - - ASSOCIATION NEWS -

“MY JOB was to lay the floor, surely I couldn’t have been ex­pected to”.. are words some­times heard when a floor fails and this is ir­re­spec­tive of whether the floor­ing is solid or en­gi­neered, on joists or di­rect stuck to a slab. No­body wants a prob­lem floor and fail­ures that re­late to in­ap­pro­pri­ate sub-floor con­di­tions of­ten re­sult in highly ex­pen­sive re­pairs.

In such in­stances there will al­ways be con­jec­ture, as so of­ten the build­ing el­e­ment or con­di­tions that af­fected the floor was not di­rectly re­lated to the in­stal­la­tion of the floor. How­ever, the stance that it was only ‘my job to lay the floor..’ is a dan­ger­ous one to take, as in­vari­ably, ir­re­spec­tive of the merit of the ar­gu­ment, the in­staller is likely to get drawn into a lengthy and at times costly de­bate. There are a num­ber of com­mon prob­lems that are ini­ti­ated from be­neath floors and it is im­por­tant that we un­der­stand these and can take the steps to avoid these sit­u­a­tions.

To an ex­tent we cov­ered those re­lat­ing to slabs in a pre­vi­ous is­sue where we con­sid­ered slab mois­ture, the height of slab above ground level and the in­tegrity of the sur­face in terms of clean­li­ness and sound­ness. How­ever, par­tic­u­larly with floors on joists there are a num­ber of spe­cific ar­eas that cause us grief which we will fo­cus on.

Wet con­di­tions be­neath a floor are a com­mon source of prob­lem. There are sit­u­a­tions where some give lit­tle re­gard to runoff into the sub-floor area af­ter the floor has been laid, even though there had been clear signs of this dur­ing the ear­lier part of the build­ing process. There are those that gain a false a sense of se­cu­rity from par­ti­cle­board or ply­wood floor­ing that they are fix­ing to and which hides what is be­neath. Long term mois­ture will pass through these sheet floors. These as­pects must be con­sid­ered and just as im­por­tant is the ven­ti­la­tion that is pro­vided to the sub-floor space.Ven­ti­la­tion pro­vides con­di­tions be­neath the floor that are sim­i­lar to ex­ter­nal con­di­tions and this is im­por­tant. While there are many floors that per­form with less than the de­sired amount of ven­ti­la­tion any­thing that causes higher than nor­mal lev­els of hu­mid­ity in the sub­floor space, which is then trapped due to in­suf­fi­cient ven­ti­la­tion, will be man­i­fested in ex­pan­sion re­lated prob­lems and cup­ping in the tim­ber floor.

Spe­cial at­ten­tion re­quired

Spe­cial at­ten­tion is re­quired when house foun­da­tions are cut into the sur­round­ing land caus­ing part of the sub­floor area to be be­low the ground level, around part of the dwelling.While all may seem fine at the time of floor in­stal­la­tion the pos­si­bil­ity of seep­age must be con­sid­ered. There are many in­stances of this caus­ing prob­lems with floors.

The sub-floor space must be dry, re­main dry and be well ven­ti­lated and if this rule is not fol­lowed then at some stage you will ex­pe­ri­ence a prob­lem floor to deal with, there is no doubt about this. Again the stance can be that these as­pects are the builder’s re­spon­si­bil­ity and they are, but it is the in­staller that has ac­cepted what has been pro­vided when lay­ing the tim­ber floor and for this rea­son the in­staller be­comes part of the prob­lem.

The sec­ond area we need to cover is the fix­ing of par­ti­cle­board and ply­wood floors onto joists. Tim­ber floor­ing is of­ten ad­he­sive bonded and se­cretly fixed to sheet sub-floors. When this is done, a com­pos­ite panel is pro­duced sim­i­lar in some ways to en­gi­neered floor­ing. With a nat­u­ral in­crease in mois­ture con­tent, the floor­ing will ex­pand more than the sheet floor it is bonded to and due to the com­pos­ite na­ture, the panel will try to arch over the width of the sheets. Hence, if the fix­ing of the sheet floor to the joists is not suf­fi­cient, it can re­sult in buck­ling with sep­a­ra­tion of the sheet floor from the joists. Most floors and par­tic­u­larly those of lower den­sity tim­bers do not ex­pe­ri­ence any prob­lems as they gen­er­ally do not have suf­fi­cient strength. How­ever, if the sheet floor­ing is not fixed strongly to the joists and the floor­ing is of higher den­sity species, then un­der con­di­tions where the floor ex­pands it can re­sult in the buck­ling of the sheet floor­ing off the joists. In­cor­rectly sized nails, poor ad­he­sive bond­ing of the sheet floor to the joist, an in­suf­fi­cient num­ber of fix­ings and the in­cor­rect screw type in steel joists are all rea­sons why the fix­ing strength be­tween the sheet floor and joists can be in­ad­e­quate. Also re­alise that nail fix­ing to pine joists will have sig­nif­i­cantly less hold­ing power than to hard­wood joists. Sheet floor­ing gen­er­ally has more fix­ings around the perime­ter than in the main body of the sheet. Due to the arch­ing of the sheet floor that can po­ten­tially oc­cur, what is of greater im­por­tance to re­sist buck­ling of the sheet is the fix­ing in the main body of it.

Con­sid­er­ing all as­pects

Again, a floor in­staller would say they did not lay the sheet floor and that you can­not see what size fix­ing was used, how­ever it is con­sid­ered that the pru­dent floor in­staller will have con­sid­ered these as­pects along with the floor­ing species be­ing laid and cli­mate in the area and had the op­por­tu­nity to raise pos­si­ble con­cerns with the builder prior to lay­ing the floor. In the sit­u­a­tions out­lined above, whether it is per­haps seep­age into a sub­floor space or the in­cor­rect screw type into a steel joist, floor fail­ures do oc­cur. When prob­lems oc­cur ev­ery­body is quick to try to hide from the is­sues. How­ever, it would be bet­ter for the in­staller, their clients and the in­dus­try if a more thor­ough assess­ment was made of what may ‘lurk be­neath the floor’ be­fore com­menc­ing in­stal­la­tion.

ATFA can be con­tacted via our web­site www.atfa.com.au by phone 1300 36 1693 or email ad­min@atfa.com.au

Newspapers in English

Newspapers from Australia

© PressReader. All rights reserved.