I am located in Bermuda and had Carlisle prepare 8″ hickory floor boards, prefinished all sides. When booking the order, we had pointed out the fact that our humidity was much higher and that the floor needed to take up a fair amount of moisture. We were assured that a good acclimatiztion period would avoid issues. This was an expensive floor.
I was a bit startled to find the floor moisture content was just above 5% on arrival. We stickered the material inside the house and covered it with breathable cloth. After 4 weeks in relative humidity ranging from 60-90%, the moisture content has come up to about 7.8%, but the boards are cupping, some of them pretty dramatic, about 1/2″ of cup accross an 8″ face. I am using a Wagner moisture meter to monitor moisture content.
We have another 5-6 weeks to go before installing the floor. Install is intended to be glued and edge nailed on plywood sub-floor, on joists. We are attempting to ensure that the MC of the plwood will be very close to that of the floor material.
I’ld be interested to have any feed back – a) is 5% moisture content for flooring prior to installation considered to be low or about right in the USA? b) any suggestions to reverse or minimize the cupping before installation or during installation?
Thanks,
James Hallett
Pembroke, Bermuda
Replies
You might want to employ this calculator: http://www.csgnetwork.com/emctablecalc.html
At 70F and 60% humidity the equlibrium moisture content would be 11%. At 70F and 90% RH the MC would be 20.5%.
5% MC corresponds to 23% humidity at 70F.
Carlisle Floor
Jim,
you say the flooring is pre-finished on all sides........is it stain /poly on the walking surface and stain only on the other three?? or stain only on all sides..?....or.....If the finishes are different on the face vs. the back side, this could cause cupping, acclimation could take longer than if the finish was consistent on all sides
Is it square edged or T&G, if T&G why glue AND nailing?? glueing could cause splitting as the wood moves seasonally. I'm assuming this is solid wood product. Since you mention edge nailing I'm assumeing T&G.
Geoff
Hi Geoff,
Finished surface is stain + tung oil + low VOC varnish, bottom and edges are low VOC vanish. Edges and ends are T&G and underside is stress relieved. Carlisle had recommended glue and nailing, presumably to reduce movement to some degree - our movement is not so much seasonal as weather related - it is humid here all year round, but the humidity goes up when weather systems come through for a few days then drops back down again.The humidity here will range from 45% to 85% with some extreme days at 95%., so part of the strategy on the floor was to leave some gap between each board to allow each board to expand and contract . Does that make any sense?
Interestingly, since first posting, the cupping has reversed a bit yet the moisture content has continued to rise. A Carlisle rep also requested that we restack the floor with the cupped boards at the bottom of the pile to exert greater pressure on the cupped boards - at the vey least that should force any of the boards with a tendency to cup into the 10% surplus.
Thanks,
James
Carlisle flooring
Hi JIm,
Since you are finished with a semi-permeable finish ( varnish ) on all sides, acclimation will take longer than if you had raw , or only stained wood. You are seeing that. Re-stacking may or may not help, time is the best cure , it's a much slower process with finished material, and each board absorbs the moisture at a rate that is related to it's individual grain and density, so some will cup more than others. Do you know if these boards are flat sawn or Quarter sawn ? Quarter sawn will be more stable and tend to cup less, whereas flat sawn will tend to move more radically.
Glueing will also be a little more difficult because of the varnish, but I am not a fan of glueing anyway, as it resrricts the wood movement in a way that could cause more damage , i.e. splits along the grain, than would not occur without the glue.
As to the gapping between boards at installation, I would not do that. I would wait until the flooring is flatened and acclimated, then wait for a high humidity day and install the flooring tight , but leave a 3/8" gap all around the perimeter, which I am assuming would be covered by baseboard trim. Leaving a gap in the field boards during install will only lead to larger gaps over time and dirt and crud getting into the gaps. By installing at a higher humidity point , you will reduce the possiblity of cupping etc. during the rest of the year and will reduce the shrinkage gaps that may occur during less humid periods, also the gap at the perimeter will allow for some movement of the wood across the whole floor,which will help to reduce the possibility of cupping occuring.
Be carefull stacking the cupped boards so as not to cause them to split because of the weight from above they will flatten on their own over time , be patient, you've got a good product there, not to mention the investment !
Good Luck,
Geoff
Hi Geoff,
Thanks for your good advice. I will check further as to why Carlisle recommended gluing. A fair amount of the material is flat sawn - possibly all of it.
James