Rigid sheet choices - aluminium or what?

[Eusebius]

Need to replace some rotten wood panels that go under some outdoor decking. It's a door that hinges up in the middle of the decking to go down some st airs to the external cellar door which is under the decking. Dimensions alt ogether are 217cm length and 77cm width. Would be easiest to split this int o three parts of roughly 750x750cm.

So need some backing sheets that are rigid but not too heavy. 750x750 in 3m m aluminium tread weighs 4.5 kilos by my calculation. The decking itself be ars the weight but the backing should be solid and shatterproof.

Wondering about something like carbon fibre, or some plastic material or wh atever - just not wood that will rot. I don't know the weight of marine ply wood, but I imagine it's similar to aluminium tread.

Ideas?

[Bill Wright]

Will the panels be upright or horizontal?

external cellar door which is under the decking.

Do you mean the panels form a door with the decking attached?

Dimensions altogether are 217cm length and 77cm width. Would be easiest to split thi

s into three parts of roughly 750x750cm.

not too heavy.

Why is weight important? Do you have to lift them up?

750x750 in 3mm aluminium tread weighs 4.5 kilos by my calculation. The decking itself bears the weight but the backing should be solid and shatterproof.

ight of marine plywood, but I imagine it's similar to aluminium tread.

Bill

[Eusebius]

Horizontal. Imagine decking at the back of a house. Under the centre part o f the decking is the cellar door with steps going down to it. So there like a trap door which hinges up so you can go down the steps. When it's closed it looks like the rest of the decking, i.e. strips of wood. You need to li ft up this trap door so it can't be too heavy. The door has strips of wood on top (decking) and a rigid sheet on the underside. It's this rigid sheet I'm talking about.

Yes

sheets that are rigid but not too heavy.

Yes. They're hinged on one side, so you lift from the other side to expose the stairs down.

[newshound]

Polycarbonate is lighter and cheaper than aluminium, and shatterproof, but it will degrade in direct sunlight over 10 years or so. You might also cover a light frame with PVC T&G cladding.

You can buy cheap plastic coated steel, either flat

or corrugated

Buffalo board is heavier and more expensive, but *very* durable.

[meow2222]

of the decking is the cellar door with steps going down to it. So there li ke a trap door which hinges up so you can go down the steps. When it's clos ed it looks like the rest of the decking, i.e. strips of wood. You need to lift up this trap door so it can't be too heavy. The door has strips of woo d on top (decking) and a rigid sheet on the underside. It's this rigid shee t I'm talking about.

Counterbalance. Very easy to do. Strimmer line, weight, pulley. Don't overs tress the line.

NT

[Bill Wright]

Floorboards, tongue and groove? 18mm ply?

Bill

[Vir Campestris]

Marine ply is no different in weight to any other ply. (which means it varies a good bit). Wood boatbuilders these days coat everything in epoxy to keep the water out. If it's in the dark (under the decking) it should last years like that.

If you _really_ want light - look at a pre-preg carbon-epoxy laminate skin over a foam core. You should be able to build a door sized bit, strong enough to walk on, under 5Kg. Be a bit expensive though ;)

Andy

[Nightjar]

I would go with metal, for maximum durability.

If you divide the length into four, hinge between the parts so that they form an inverted W when part open, you could slide them along tracks from the top end of the steps. The only lifting needed would be at the two upward hinges, just to get the opening started.

[Eusebius]

That's a bright idea, and so is counterbalancing the door. Some real brains on this group as usual!

[meow2222]

I'd expect debris in the tracks - no problem when its leaves, but could be a pain when its stones, depending how is designed. You could just divide the flap into 2 halves to reduce weight.

NT

[Nightjar]

If the sheets drop into a recess and cover the tracks, it shouldn't be a problem. In any case, for outdoor tracks, you are always best off using grooved rollers running on an inverted T or V rail.

[meow2222]

but will be

yes

NT