Thread: Help in Building Granite top Desk

That's 70 kilos of granite - your biggest problem (aside from moving it around) will be supporting a sheet of 30mm thick granite so that it has zero tendency to sag (rapidly followed by cracking) over 1500mm once you factor in someone standing or sitting on it one day.

The maximum unsupported overhang for granite benchtops is like 300mm, so I'd be doing some serious testing of support beam sizes to make sure you find something that won't deflect under load. I don't think you'll get away with anything less that about 40-50mm thickness to keep deflection under, say, 1mm.

Master splinter has summed it up well. I know your preference is for timber, but given you also require a minimal amount of support structure visible, my suggestion is to seek advice from the Metalwork forum. The hairpin legs appear to be steel, so welding them to an appropriate sized frame would seem to be the way to go. Good luck.

I just realised that it's going be 60 to 70kg weight. That's a lot of weight for desk. Maybe I should look for thinner slab say 20mm one.
At least that would cut down the weight to around 45kg.
Say if I use 20mm slab instead, what sort of wood thickness would be preferred?

About the steel alternative, I think that would be cost ineffective for me at this stage as that means sending it to be welded with extra beams. I'd probably opt for thicker timber support solution.

35mm timber should do for 20mm of stone. Steel may cost more, but it will be much stronger.
Even with timber I'd still be using steel bracing.

Alright then. We're still waiting for the slab options before we can pick which granite to go with.

For the timber itself, what sort of timber do you recommend? Furniture grade plywood still a good option at this stage? Or should I go hardwood and a bit thick one so it won't bow? But I don't think bunnings got dressed hardwood.

I did have a table like that with the same legs. Roughly 19mm x 1200mm x 450mm in marble. Ply was 12mm, legs light wire, glue bog standard silicone. It was a display table that became an outdoor table and now sits in a lounge room on wooden legs. 30mm is too thick for spindly legs, anyone that sits on a thin piece of granite should be castrated, you don't want that level of stupidity breeding.

Haha don't worry no one is going to sit/stand on the desk. It will be my computer desk. What timber you use as base? Do we need to use furniture grade to make sure that it's level and glued evenly? (I don't have the resource to smooth the board)

The original base looked like marine ply, the remade table had a base of chipboard flooring because it was handy. Wood surrounds hid the chipboard, it no longer lives with me and the remake was by someone else. The main thing I would be worried about is your design being top heavy, you don't want it toppling onto small kids. 20mm thick I would be a bit worried about it snapping over that width when it is being used as a desk, have a look at some of the marble topped furniture made over the 20th century, generally it had good support underneath and a stable base. I've done quite a bit of work with stone, what you are planning is not something I would be that keen on in ply. Perhaps the steel suggestion might have merit. Generally you don't fix the top to the base it remains loose so it can be removed for transport. You would need to protect it from the steel though otherwise you run the risk of rust bleeding through the material.

Cool thanks for the tips. I'll make sure that whatever material I use is sturdy and wide/thick enough to cover the whole slab

you might be able to get the granite with a laminated edge, so it looks thicker, but without the weight of a single solid piece.

UPDATE
So I've bought the following :
- 20mm granite slab 1500 x 500
- 25mm structural Plywood (for the base): 1240 x 420

The plywood is just 1 piece, so I guess I don't need to reinforce this? I will screw the legs to the 4 edges of plywood, and then glue the granite to plywood base, and let gravity spread the weight to the 4 legs.

I hope it would be solid enough. To glue the granite to plywood, what glue do you recommend? Thanks.

Silicone will do the trick, plenty of squiggles though