Thread: Jarrah Kitchen Benchtop Advice needed

If it were me, I would treat the jarrah and substrate as two parts. I'd either glue the tongue and groove together to make one solid panel, or machine the t&g off to give a flat face to joint up to. I would then fix the jarrah with screws from underneath through the substrate with over-sized holes with washers under the screw heads to allow for movement.

Is it a corner bench, island or something else? You have options to fix the floating top down the center and allow it to float front and back on an island bench, effectively halving the movement. If it backs up to a splash back, you need to seal from the bench up the back so I would fix the back and allow the front to float in and out.

I might be wrong here, but if you seal it well (both sides and especially the ends) you should get less than 5mm movement over a 600mm bench top (~1% for hardwood but that's very rough)
Any refinement to those figures is welcome.

I find movement estimates very difficult because so many variables come into play. Even for a particular species, how dry it is and how long it has been that dry for seem to play a big part. If they are old (20+) recycled boards, I would say there will be little movement at all. If they are new there will be much more (up and down)

Im pretty keen to hear others thoughts on this one too, good luck!

here is a table we made from tallowood flooring.

we glued the floor boards togther in the factory by glueing the T&G togther with a marine glue.

the threee sections where then sanded flat using our wide belt sander,

we then made a steel frame which was clad with one layer of 17mm plywood.

the sections of tallowood were then glued to the ply using a polyurthane timber floor adhesive which was trowel spread.

we then put a few screws in from the bottom to hold in place while the glue dried & we clamped the next section togther.

the edge is 70x70 tallowood which is mitered on the corner this was glue & domminoed to the top.

Thanks for your detailed advice Robomanic. I've added a basic drawing of the benchtop here to make the project a bit clearer.

Attachment 186631

I was thinking along the same lines, ie to make the laminate up as a glued board and then allow it to float on the particle board, attached only by screws, however Gaza has shown a great table made from floor boards that were glued down directly to 17mm ply board. Gaza - Why were there three sections in the table top design. Was that somthing to do with minimising the effect of movement between the different timbers?

If there is going to be movement in the timber I believe its only across the grain - is this correct?

[QUOTE=Handydaddy;1396430] Why were there three sections in the table top design. Was that somthing to do with minimising the effect of movement between the different timbers?

QUOTE]

the table is 1.6mt wide by 3.0mts long it was in section so it would fit into a lift on the angle as this table is installed on level 52 of office building.

also meant we could carry it.

[quote=Gaza;1396438]

Originally Posted by Handydaddy

Why were there three sections in the table top design. Was that somthing to do with minimising the effect of movement between the different timbers?

QUOTE]

the table is 1.6mt wide by 3.0mts long it was in section so it would fit into a lift on the angle as this table is installed on level 52 of office building.

also meant we could carry it.

Dohh should have thought of that !

I have used floor boards too, in a kitchen bench top. Looked great I reckon. We fixed it to the front and allowed it to float at the back.

Hi tea lady

Did you lay your floor boards on top of something like Ply, Particle board or MDF and how did you fasten the two together?

I don't know how tight your budget is but in my opinion you are much better of laminating two layers of Jarrah flooring instead of fixing it to chipboard. Even if the underside is of a very low grade Jarrah (should be pretty cheap then)(do make sure you leave them to reach the same moisture content before laminating). That is the best way to avoid a curved bench top.
Good luck!

Also... the way you are going to butt join the sections together, it will be very noticeable if there is any cupping going on.

the price you will pay for t&g flooring and the substrate you could buy recycled jarrah as in old bearers and joists... look around for some house demos and hit them up.

I think you worry too much, I built benchtops with redgum as you are planning and not had an issue in 3 years. I also resurfaced my computer bench using decking boards and that has not shifted.
trees dont grow taller or shorter with moisture so the main expansion is across the top which is not that wide. So if you block moisture getting into the top as you should on a kitchen benchtop the thing will not move.
I painted the bottom and the cut out for the sink and oiled the top with hard burnishing oil. That I repeated several times when it looked a bit dry and it builds up a skin over time so needs less attention. The Merbeau top I used dewaxed shellac and that has never needed more attention.
The T @ G boards may be an issue, I have a jointer and jointed then used biscuits on my top, whether you can get a razor edge with T@ G will be your problem. Oh and sand the wax off the yellowtongue board.

I agree with rrbor. I think there are other issues here apart from the possibility of relative differences in unit shrinkage rates between jarrah and yellow tongue chipboard. I'd be sawing off the tongues and grooves of the jarrah and I'd be straightening and sqaring the edges of the resultant square edge boards. T & G Flooring product was never designed as an edge gluing product and is not made to the straightness tolerances required for fine joinery work. Then I'd join the boards with biscuits or Dominoes or with a zig zag spindle moulder cutter. Probably a good idea to join up the sections to +/- 300 mm wide and then join those.

Yellow tongue is designed as a sheet flooring product with short duration exposure resistance. You should really be using HMR chipboard given the wet area nature of kitchens.

I'd just bond on the 600mm wide jarrah to the chipboard. I'd normally go for marine epoxy or AV 180 but you will have to seek out a product that will bond on to the semi water proof surface of yellow tongue. I don't know what that product is.

In summary the key here will be to use well tried and known joinery practice to join up your jarrah in a manner that doesn't build a bunch of stress into the jarrah panels that will want to release at some later stage. It's not a big deal to get this right.


Good Luck

Old Pete

Originally Posted by rrobor

I think you worry too much, I built benchtops with redgum as you are planning and not had an issue in 3 years. I also resurfaced my computer bench using decking boards and that has not shifted.
trees dont grow taller or shorter with moisture so the main expansion is across the top which is not that wide. So if you block moisture getting into the top as you should on a kitchen benchtop the thing will not move.
I painted the bottom and the cut out for the sink and oiled the top with hard burnishing oil. That I repeated several times when it looked a bit dry and it builds up a skin over time so needs less attention. The Merbeau top I used dewaxed shellac and that has never needed more attention.
The T @ G boards may be an issue, I have a jointer and jointed then used biscuits on my top, whether you can get a razor edge with T@ G will be your problem. Oh and sand the wax off the yellowtongue board.

Originally Posted by old pete

I'd normally go for marine epoxy or AV 180 ........

Old Pete, I find it interesting that you've used marine epoxy and AV180 in the same sentance. Is AV180 considered water proof or water resistant?
Or have I missed the point you're making?

As a structural products executive for a major particleboard manufacturer and timber mill for many years, I would like to add a little to the debate. First, particleboard flooring has a waxed surface to assist with weather protection. This surface needs to be removed (sanded) if an adhesive is to be used. Second, particleboard flooring is a three layer product which responds poorly to single side laminations. The old five layer board responded much better. I dont think anyone makes it anymore.
May I suggest an alternative approach; Rather than using the floor boards on flat over a substrate, what about ripping them to 35mm and glue laminate with the strips on edge? This would give a 35 mm thick benchtop made up with 19mm strips. With this technique, even second hand flooring can be used as the nail holes are not visible on the surface and carefull selection of a nail hole free edge piece makes all look pristine. Epoxy glue the strips. May be easier to glue up half widths (300mm) at a time and then final glue the two 300s together to form the 600.
Hope this helps