Screw & plug fixing

[rick]

Apologies if this is a bit long .... looking for some advice on plug & screw fixing. I have a large quantity of raised garden beds ... so effectively a 100 wide brick wall. On advice here - I will be fixing 5mm plastic spaces to maintain an airgap (keep wood off brick) ...... end result will be:

Also on here have purchased 152 x 7.5 concrete fixing screws

I will counterbore holes so I can glue in wood plugs ... intend using router to do this.

There are 2 approaches ...

Fixing option A

Where screws go in at 90 degree, would mean I need a jig of some sort to match angle of sloped section.

Or I simply dill in at 90 degree to surface of angled section - meaning fixing will be angled. Fixing option B

This 'may' give a better fixing, and would mean no jig needed router would go flat on sloped section. Welcome thoughts on this.

Secondly ....... Screw is 11.1mm across head ......... so need to counter bore to 12mm (or 1/2")

Option would be to use either a screw digger:

with plug cutter:

concern is only tool steel, and more than 200 plugs to cut.

not sure if these would be any better:

Welcome advice from those that have used these before.

[stuart noble]

A couple of thoughts. The nosing looks like the key, or rather the joint between the nosing and the "sill". Add on bits, trims, or small sections generally don't work well where wood is concerned. I would rout or circ saw a groove on the underside instead. Neater, more effective and certainly longer lasting IME. I've always used dowelling instead of plugs on the basis that ramin is infinitely longer lasting than anything you're likely to cut plugs from. Have them a bit longer than required, hammer them in, and redefine them as "pegs". Rustic ennit?

[rick]

The nosing serves 3 purposes ...

# creates a drip # neatly covers gap between top of cladding & cill # makes leading edge the same thickness (appearance of rear edge)

I have the nosing here (also treated) ... not decided yet how to fix ... probably waterproof PVA and pin with nail gun at 300mm centres.

My biggest 'ponder' is whether to fix with 2 screws as drawing options ... of just one screw at centre line of brick .. every 600mm