Hardwood timber is pricey here in the UK, so I have been investigating a number of alternative sources of hardwood for small home woodworking projects - including recycling of pallets and furniture, but also, buying and repurposing stock materials that were actually intended for other uses.
One of these stock materials is hardwood flooring - usually fitted as a non-structural floorcovering over the top of a structural floor - this sort of stuff - typically metre-long boards made up either from sawn planks, or comb-jointed smaller pieces glued and pressed, but still solid timber.
I ordered some free samples to evaluate it for my purposes (actually, I’m most interested in the bamboo variants). All of the samples are finished flat on the face side, obviously, but they all have two shallow furrows or grooves on the underside - almost like roller marks from compression or feed through a thicknessing machine.
I don’t think they are compression marks though - I think they’re actually cut into the undersurface of the material. Here is a representative cross section that shows the grooves clearly.
What are these grooves for? Are they to accommodate glue squeeze out?
As far as I can tell, the original reason was to relieve stress and prevent ‘cupping’. This is not valid with today’s processing methods and it is still done because tradesmen expect them and would reject flooring timber without them. They also make it easy to see which side is up.
Some people suggest that it’s for excess glue, but my floors are not glued, but ‘float’ over the original floor.
We put engineered Bamboo flooring down in a few areas of the house when we renovated - Kitchen, Front Entrance, and Laundry.
Awesome, stylish and affordable.
And flaming hard - I had to be very careful when I was drilling to fit the track for the laundry cupboards. In fact, I tried to polyurethane the laundry - the installer was very clear the use of the flooring was not recommended in a possibly wet area like the laundry. After the first coat of polyurethane started flaking the next day, we gave up. Most of it has already flaked away over the last year.
And like bob++ said, it is a floating install over a neoprene barrier sheet.
I’m actually looking at strand-woven bamboo - seems like a very interesting product - rather than cutting rectangular-section pieces and regluing them into boards, they split and crush the bamboo stalks, pile them into a big metal box, add resin and compress under massive pressure - the result is a solid material that looks and (apparently) behaves a lot like solid timber - it has good strength because the fibres are more or less longitudinal, and it seems it can be sawn into planks just like wood.
I need to run my samples through a planer/thickenesser to see if I can a)get rid of the grooves, and b) remove the surface coat that’s been added for flooring use.
It does relieve stress, and that helps the flooring conform to uneven surfaces when nailed or glued.
Mangetout, why do you need to remove the grooves? Are you just trying to get thinner stock? Are you using this for something besides flooring? You need to be careful planing engineered materials, they could wear out your planer blades quickly or delamination could occur in the planer making an unholy mess.
I want to make things like boxes, where both faces of the timber will potentially be seen - and it’s driven by a combination of economy and curiosity.
Point taken about working with it and damage to tools - I’ll give it a try on a small scale with hand tools before diving in any deeper. I’m not planning to use the engineered varieties or laminates (although of course all of these materials are ‘engineered’ to some extent).
Strand-woven bamboo dimensional lumber is available in some places, just not readily available here. I’m fairly sure it should behave at least a bit like timber.
I did some testing on my samples - results here (video).
Both the solid bamboo and strand-woven products behave analogously to wood under a a range of different tools. The strand-woven stuff is pretty hard and tough - and I expect it will have a blunting effect equivalent to some of the more dense and heavy hardwoods.
and here i thought the grooves might have allowed for placement of radiant heating elements in the grooves. in hindsight, i can see why this would never have worked … but definitely got me chewing on my tongue.
I always assumed that it was for the same reason that large ceramic tiles have the same kinds of grooves. Which I was told, was to provide greater surface area for glue.
But maybe with wood, it’s to allow air to circulate a bit under it, to prevent moisture buildup from undermining the floor.
Wood breathes. IIRC, the underside is not finished. Wood will expand and contract with humidity - so more surface area, quicker adjustment to the ambient humidity? (We were warned to get a humidifier for the winters for our solid maple strip flooring) Plus with thicker solid wood, it makes sense that the grooves would reduce the incidence of cupping. If it’s like mine, the wood has tongue and groove edges to grip the neighbouring board; the board is hammered onto its neighbour with a rubber mallet, then an angle impact nail driver (?) will nail the board to the subfloor through the exposed lower edge of the side groove every foot or so.
