Filling knots in Oak flooring

[WoodyNZ]

Hi all

I've recently laid some Oak flooring at our house and I'm looking for advice on filling some large knot holes.

We've laid about 50 sq mtrs all of which is over concrete. We've gone with a very rustic grade timber, partly because of price but mostly because we wanted the knotty look. I do need to fill the knots but we want to keep them as a feature of the timber. The knots are up to a few centimeters in diameter and there are lots of them - hence I need a cost effective solution.

The floors will be stained (fairly dark) and oiled afterward, not polyurethaned.

I've heard some ideas about using coffee grinds (I can generate as much of that as required). I also have more Oak sawdust than you can shake a stick at. I've done a few searches on this forum but I'm still a bit confused. Some seem to suggest epoxy, which will go very hard, but is rather inflexible. Will that be a problem with expansion/contraction over the seasons? Or maybe the timber won't move very much anyway as it's glued to the concrete base. Also, if I have to do the whole floor using those little two part epoxy tubes from Bunnings then it will get very expensive.

There seem to be a variety of wood filler products on the market, but are any of these hard enough to handle being walked over every day?


Thanks

[justonething]

G'day Woody,
epoxy when dried will produce a very tough surface, and flexible enough to allow for your floor to move during to expansion and contraction. So that shouldn't be a problem. You will need to try out if a epoxy covered surface and a bare surface will give you the same tone with regard to your stain and adjust accordingly, preferably on a few test samples.
There are cheaper supplies than bunnings. Try your marine services. http://www.adhesivetechnologies.co.nz/west.html. Use 105 resins with 207 clear hardener would be what I'd start off with.

[WoodyNZ]

Thanks justonething. Appreciate the advice.

[justonething]

You probably should stain it first before filling. See what you get with your test samples. trademe would also be a place to shop for epoxy.

[Xanthorrhoeas]

Hi Woody,

I would also recommend epoxy but suggest that you look at Boatcraft Pacific who have EPOX-E-GLUE, which is an excellent epoxy for filling large gaps (they call it thixotropic). http://boatcraft.com.au/informationpages/epoxeglueTDS.htm

I use this with a coloured filler to match the colour of knots in timber, or the timber itself (depending on whether a knot or a crack). You can buy natural earth pigments fillers in many different colours on eBay. I purchased from a UK company called Endless Green Group Limited and they are connected with a company called Bolgers who supply in larger quantities. An eBay search lists some other suppliers in the UK and also shows some Australian suppliers though I am not clear from the description if they are ground finely enough. There may well be other sources. I mix up a tiny amount of the pigment with the adhesive - a small amount goes a long way. Make up a sample with recorded amounts of pigment to set amount of epoxy and let it set to see the final colour in an off cut.

[Christos]

Normally when filling knots or splits in timber there could be a chance that the split goes all the way thought. As the floor has already been laid it might be worth seeing if this is the case and make note of these holes to pack with something.

I have used plasticine but for only one project as I was curious.

If you go in this direction the epoxy needs to be tinted(or mixed with sawdust) to ensure the colour of the plasticine does not show through.