Wood movement and moisture –
I have a flooring manufacturer in New England telling me that her product moves less with changes in moisture content than “ordinary” wood flooring on account of:
– being slow grown northern stock
– being slowly and evenly dried first by air, followed by drying low temperature kilns
is there any validity to these claims? Should one expect the moisture coefficients for flooring from this source to be less than coefficients published in standard reference books? If so, by how much, roughly? I’ll have a look at Bruce Hoadley’s Understanding Wood when I go home tonight, but I’d really appreciate any way you might help me to sort out what the saleswoman is telling me.
Wood is wood no matter how it is dried. It will always attempt to come into equilibrium with the relative humidity in which it finds itself. The amount of movement is based on the species, not the method of drying.
The individual's claims are likely hooey but if you want to have some fun -- ask for the data/study that substantiates her allegations!
Northern red oak has radial/tangential shrinkage values (between green and Oven-dry of 4.0/8.6%. Comparatively Southern red oak is listed as having 4.7/11.3% but Pin oak is 4.3/9.5% and Scarlet is 4.4/10.8. The problem is that once cut, there is no way to differentiate one red oak species from another; and the values listed are averages that have incredible variability within the sample. Thus species is a factor but so to are density, genetic variability, site, soils, competition, age, location within the tree and micro-climate.
As stated previously, drying methodology and practices do not significantly change shrinkage/expansion coefficients.
Follow-up question. Wood (sorry) the drying method have any effect on whether it expands gracefully or twists?John O'Connell - JKO Handcrafted Woodworking
Life is tough. It's tougher if you're stupid - John Wayne
The grace of a wood's expansion will depend entirely on the quality of design into which it is incorporated.
Regarding twist, in some instances, the wood will dance to its own tune.
This discussion begs a question that came to me during my current research into which type (species of wood) flooring to choose for our remodel project.
One manufacturer (who's web page I visited) produces a three ply solid wood product. I imagine this is in order to be able to use a higher quality/grade on the exposed face and less good material for the other two plies. There was no information about how the plies were oriented whether cross grain ala plywood or with all the grain parallel.
Assuming for a moment that the plies were cross grain laminated, would that then to produce a more stable product in the same manner that it does with plywood? Given a 3/4" thick plank of flooring, the plies would presumably be 1/4" thick. Would this be too thick to produce the stabalization achieved with more and thinner pieces in regular plywood?
Dennis in Bellevue WA
I felt that the discussion dealt with strip flooring rather than laminated material.
You are however correct that laminated flooring is somewhat more stable. In most instances it is pre-finished in the factory as well.
The top grades of strip flooring (oak) are quartersawn. 3 ply laminated flooring is entirely rotary peeled (tangential). The veneers are layed-up into plywood sheets and then these sheets are ripped to the generally 3, 5 and 7 inch widths, milled to pattern in a matcher and then end-matched with tenoners.
As it is a thinner product to begin with; the plys are less than 3/16" thick which precludes on site sanding and for the most part sanding/refinishing at some later date when damage does occur. Most complaints/damage are associated with the earlywood -- in tangential faces, there can be large areas of earlywood that is less dense and more porous. It wears faster and is more prone to scratching as from the nails of large dogs.
The grade yield from oak peelers used in flooring veneer production produce a pretty consistent product mix -- slightly less than 1/3 is face grade, slightly more than 1/3 is back grade and the remaining third is core stock. I don't know if this is happenstance or whether the grading rules were developed to produce this mix.
As a product, I think it suitable for dining areas and bedrooms but I would be skeptical about using it for entry ways/foyers or other high traffic sites. You also are restricted to the color choices available and lay-outs that use the typical 3, 5, and 7" mix.
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