Levelling the top of a wooden structure

They won't be in sunlight?

They would be, unless I masked the open gap between the current and the new top surfaces, or positioned the fixings sufficiently far inside the edges to avoid the sunlight. And if the supplied screws are unplated steel they'd probably be vulnerable to rust in the salty seaside air here.

Screwfix and Toolstation (both near me) stock them, but not in the mini size, annoyingly. I might ask to see them though, to judge the materials.

Alternatively, maybe I could approximate the effect and get the same adjustability (albeit in a rather more fiddly way) with stainless steel bolts and nuts.

You can use stainless steel screws with them.

Bit late on this! Securing plywood sheeting over foam insulation, I used screws sold as *stand off* fixings. Basically a short length of conventional woodscrew a plain shank then some circular retaining ridges under the head. Fitting technique was to fully tighten the screw to engage the retainers and then back off; moving the retained sheeting to the required position. Today, a search on *stand off* screws finds zillions of advertising hoarding fixings and circuit board spacers:-(

Something else I'd never heard of; thanks.

I fixed some wooden tops on to fence posts with pink grip: it took only a couple of years before the tops became loose. The pink grip had cracked and crumbled. Enough of the fancy stuff - st. st. screw did the job. I used pg to fill inunder the top to keep out water. I feel that a slghtly flexible, UV-resistant, material would be better. No Nonsense Exterior Frame Sealant seems to be good. I've used it to seal around things mounted outside on rustic bricks: do top and side; leave bottom open for drainage/ventilation.

Thanks for that. I'm going ahead with a top sheet of 3mm aluminium, screwed down, with the slope set by spacers and the void filled with either adhesive or sealant. From what you say, sealant would probably be the better choice.

With ali you have an impermeable surface - so the glue won't be constantly wet, and the timber it is screwed two ought not change dimensions as much due to moisture changes in the wood.

So a building silicone or frame sealant might work well - or failing that cut some thin firing strips[1] with a wedge profile that counters the slope of the original surface, leaving the ali level. Then you just need a mechanical fixing and there is not need for additional spacing "gloop".

That's the route I've chosen, with a sealant infil.

I've not encountered that term before, so thanks for teaching me something new.

Basically (long) tapered strips of wood...

Commonly used when you want a "flat" roof for example. You set the roof joists properly flat so that your structure is square, and your interior ceiling will be horizontal and the room the same height on all sides, but then place firing strips on top of the joists to add the slight slope you need so that the roof will drain properly.

E.g. when I did my loft, I used 6"x2" roof joists for the rear dormer roof section:

Then set the thick end at the ridge of the roof, and the thin end at the eves:

Thanks. Actually, I picked that up from your description, but I was intrigued by the name.

Should be fiRRing not FIRING

Yes sorry, mea culpa. I should not have bowed to the spell check overlord!

-- Cheers,

John.

/=================================================================\ | Internode Ltd -

That explains my puzzlement, though it's still an intriguing name. Thanks.

Sometimes seen as "furring" as well (which better reflects the pronunciation)

-- Cheers,

John.

/=================================================================\ | Internode Ltd -