kitchen solid bench top corner problem.

[DJ’s Timber]

I'm interested to know how many timber bench tops your boss done using a mason mitre? Can you go and see any that he may have done and how have they held up?

I have done a few bench tops using a full mitre and haven't received any callbacks yet and this includes laminated and full width slabs.

Ask around and see if there is any locals with timber tops and if you can get permission to see them to give you an idea of what has held up and what hasn't.

[JDarvall]

Sorry, I'm probably going on about it too much. Just can't really afford to stuff it up.

I get fridays off. So, I'll ask him monday.

He's visualising it, like I did initially, that any movement will open it up.

At smoko yesterday I brought it up again, and from what I gathered, his idea was to epoxy up just around the mitre (mason mitre) and let the rest of it float towards the wall. But that made me question him on there being too much movement at the wall for the seal. ???

Seems to be two lines of thought on this one. anyway.

[arms]

ahh the idea ,worries me greatly when people think about what to do and then ask someone who tells them that this is the way that they would do it ,then the someone takes the advice on board ,then when it may or does go wrong they say well you should have made your own decision.
coat all exposed esges with whatever finish you are going to use ,do not do this sparingly as you will be sorry,timber tops for for that matter anything timber HAS to be allowed room to move ,to not do so is to your own waste of money

[JDarvall]

Want to say, I am appreciative of all the ideas. I won't be blaming anyone, except myself should it stuff up.

Wondering what would you do Tom ? ....big butt joint, mason mitre, or just a big mitre at the corner. Sounding like you'd prefer to just butt it (?)

[journeyman Mick]

Jake,
I love working with timber but I don't generally recomend timber kitchen tops to my clients for a couple of reasons.
1. It's quicker and easier to get the job done and the cheque in my hand using pretty much any material other than timber.
2. Cross grain joint problems/expansion/contraction issues.

I won't mitre the corner joins - ever. Relative humidity here swings from 100% in the wet season down to about 20% in winter. There's a lot of potential for movement.

Did a "L" shaped timber top not too long ago. It was a butt joint with biscuits to align it and metal benchtop connectors to pull it together. The cut outs for the connectors were made with elongated openings to allow for movement. The first piece was fitted to the cabinets, screwed from underneath with the screw holes at the front of the cabinet elongated to allow for movement from back to front, which is pretty standard.

The second piece was then fitted and pulled up tight with the metal connectors (after all surfaces had been coated, of course). The holes in the cabinet for this piece had to allow for movemet of this piece (back to front of cabinet) but also had to allow for the movement of the other piece (along the grain of this piece). So all the holes were drilled hugely oversized and screws went through a piece of ply as a washer. Our wet season has started and they've had no problems and I don't anticipate any.

I hope my explanation has been clear enough, some diagrams would probably be helpful but I can't drive any of the drawing programs and my scanner is buried under a pile of paperwork.

Mick

[arms]

Want to say, I am appreciative of all the ideas. I won't be blaming anyone, except myself should it stuff up.

Wondering what would you do Tom ? ....big butt joint, mason mitre, or just a big mitre at the corner. Sounding like you'd prefer to just butt it (?)

what mick has said is correct ,butt joint ,elongate holes ,oversize washers ,this is the industries recommendation so i would recommend you go with the people that know what to do and are willing to share their knowledge with you

[Dirty Doogie]

HI Jake,

I have been watching this thread and your kitchen querie since it started but havent posted becuase my experiences with making a hardwood kitchen benchtop have been largely negative or at least a trial.

I don't want to say don't do it becuase if it works a Blue Gum benchtop is a beautiful thing. All I will do is recount my experience.

About 15 years I made a kitchen for some friends. In the design stage it was decided that the benchtop would be made from some old dressed blue gum boards my friends father had been keeping under his house for 30 years. The boards were machine dressed to 140 wide x 32 thick and had been kept very straight, dry and clean. The timber had been back sawn.

I glued and dowelled 5 boards together using Resorcinol making sure the radial grain alternated on adjioning boards. The benchtop was L shaped 2100 x 2700 and I put a mitred corner and used benchtop jioners (bolt type). The corner was total PITA and had to machine planed and sanded to get the boards level with each other.

Before installing the benchtop I sealled the underside and end grain with polyurethane clear finish and the top was finished with a non yellow Poppyseed oil (from artists suppliers) and polished to a satin sheen.

Now to this day I really dont know what happened or why - but 6 months later - cracks began developping in centre of the boards and ran from end to end AND the mitre opened up. The splitting continued over the next summer. At first I went over and filled the cracks and refinished - but was very disappointed as was the friend.

Finally it was decided to replace the homemade benchtop with a factory made timber top. At the time Hyne timbers made red color select grade hardwood laminated benchtops and my friend spent $1800 on a new 35 mm thick top.

The timber expert at Hyne told me that the problem was probably that my pieces of timber were too wide and generated too much movement according to humidity. And that stable benchtops needed quarter sawn material cut down to a square or almost square shape - seasoned of course and glued hot .

I have never tried a 30mm thick + hardwood timber benchtop again - but the laminated benchtop from hyne's is still flawless ( well last time I saw it 3 years ago).

I have since then made a red gum benchtop from 15 mm thick x 120 mm wide boards glued to 32mm MR fibreboard without any problems ( including mitre)

So that is my experience - hope your bench is better behaved.

Doog

[journeyman Mick]

Doog,
what a bugger! Can you recall if the cracks were only in the top face or if they ran right through the boards top to bottom? I'm wondering if the problem may have been caused, at least in part, by there being different finishes top and bottom. I'm not familiar with poppyseed oil at all but I'm guessing it was able to absorb more moisture than the polyurethane and it certainly would have been exposed to more moisture as the top face. That said, I can't understand the cracking, one would expect a cupping or bowing.

Mick

[Dirty Doogie]

HI Mick - over the years I have wondered the same thing about the oil - the cracks started out as fine fissures on the top surface but by the end of the first summer had gone about 30% the way down and had actually gone all the way through at the mitred corner.

Poppyseed oil is a hard finish oil that they used to make artists oil paint and old fashioned white house enamel from, especially light colors becuase it doesnt yellow. I have used it on other moisture senstive timber like hoop pine without any problems.

The way I look at things - if something doesnt work but you've learnt something (even if it is to never try it again) then it hasnt been wasted time LOL

[JDarvall]

I was wondering Doog, .......How did you fastern the bench to the frame ? Did you have it so the wood could move freely around the fasterners ? Thinking that may explain it.

Sorry to bring up questions about something you probably want to forget.

[journeyman Mick]

Doog,
my guess is that even though the timber was well seasoned it's moisture content was greater than the environment in which it was eventually fitted. The poly would have been close to impervious to moisture, at least compared to the oil. So the top surface started drying out whilst the timber below stayed where it was. The timber below didn't allow the top surface to move so small fissures opened up. As these fissures opened up they allowed more timber to dry out, but the bottom face was still impervious and unmoving. This resulted in major cracking. The mitre would have opened up regardless of the finish. As the timber expands or contracts the angles at the end of each piece change so that they're no longer at a true 45 deg. resulting in a dodgy mitre. Be interesting to see if anyone else has any other explanations for this failure.

Mick

[Dirty Doogie]

Hi Jake - the carcasses were MR chipboard and the bench top was fixed to the cabinet sides by 35 x 35 x 150 long angle brackets screwed on. As I rememebr there were only 4 or 5 of these brackets for the whole job. The brackets were fixed mainly under the centre plank of the benchtop leaving the other planks to move around.


Hi Mick - I would have thought that the humidity in the kitchen would have been quite high and the first summer was very wet. Perhaps it was due to some difference in "breathabilty" caused by different surface finishes that did it. Never the less I have never seen hardwood crack like this before - even in structural work where stresses would be much greater.

AS it turned out I cannibalised the old blue gum top and made some sliding timber window frames out of it without any great problems.

The 2 or 3 timber bench surfaces I have made since then by laminating thinner timber onto man made board, using good old sikaflex, have worked perfectly with difficult timbers, RED GUM and Northern Scribbly Gum (E. signata).

[JDarvall]

. As the timber expands or contracts the angles at the end of each piece change so that they're no longer at a true 45 deg. resulting in a dodgy mitre.

Thats it in a nutshell I origionally thought...all mitres seem subjected to this. Sounds like your probably right about it being a worry due to the moisture swing here.

Thanks doogie for the explaination and everybody else.

So i wont be mitring it. Seriously considering not having a solid bench top now at all. I don't like butted slabs. Sounding like dramas. Might use the blue gum for something else.

[Dirty Doogie]

I didn't mean to put you off the idea Jake!

I think the timber guy from Hynes may have been on the right track though - my boards were too wide and/or thick and the grain travelled the wrong way through the boards. When they boards wanted to move the edges were stuck rock solid so stresses built up along the center.

Why not try the benchtop with narrower sections? I always meant to try it that way myself - but never got around to it.

Maybe not have a corner return section ?

[juan]

Great discussion guys. You have helped me decide on my new kitchen benchtops. Caeserstone or granite.