Plug & Screw fixing (lots of them)

[RickH]

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.
I will be fixing 5mm plastic spacers to maintain an airgap (keep wood off brick) ......
end result will be: http://tinyurl.com/zfxjsar

On advice decided to use 152 x 7.5 concrete fixing screws http://tinyurl.com/z9g7scr
I will counterbore holes so I can glue in wood plugs ... intend using router to do this.

There are 2 approaches ...
Fixing option A http://tinyurl.com/zzkvu2u
where screws go in at 90 degree, would mean I need a jig of some sort to match angle of sloped section.

Fixing option B http://tinyurl.com/hrmgkkr
Or I simply dill in at 90 degree to surface of angled section - meaning fixing will be angled.
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: http://tinyurl.com/zxeef7h
with plug cutter: http://tinyurl.com/jm8qv65 concern is only tool steel, and more than 200 plugs to cut.
not sure if these would be any better: http://tinyurl.com/jjb8jnz

 

[chappers]

total over kill for fixing a 50mm bit of wood onto the wall.
You're over thinking this and over engineering.
First get a 12mm spade bit and drill a single hole down about 20mm into the timber along the centre line of your wall, probably just on the start of the slope of your timber cap. keep it vertical by eye. This will take an off the shelf wooden pellet but if you want to be sure they match better then buy a plug cutter and cut from offcuts of your timber.
next drill through the centre of the hole with a 7mm drill bit, drill through this into the brick with an SDS, fit a brown plug and fix with a 4" screw.
If you try fixing two big frame fixings like that into a single leaf wall, there is a good chance you could end up splitting some of your bricks

 

[RickH]

Appreciate your comment but fixing with plugs is not the way I am going to do this ... many people have advised that direct screw fixings are safer & stronger and much less tendency to burst the brick.
Screwing into a plug tends to expand the plug ... concrete screws cut a 'thread' In any event I have now bought the screws.

I would never use spade bits for joinery work ... they do not cut neat holes. Roughing out a hole for a coach bolt where head covers the hole then fine.

Maybe 1 central screw will be enough .. and 600 centres .............. wa sonly going to use them in pairs after advice here,.

 

[Dave54]

Spade drill will cut a clean hole if you get the sort with "spurs" on them, or file or grind the spurs on a "plain" one. Most will file. Another option for a hand held drill is a brad point drill. In either case use a light touch when starting the hole. Tapered plugs will fit tighter than straight ones.
No reason why doing it this way should result in a "rough" job.
I'd have used plugs personally, and tried to position them into the brick rather than the mortar joint, but I'm old fashioned. I'll bet that cutting the "thread" with the screw puts a fair bit of expansion pressure on the hole, but you've bought the screws.

 

[Burnerman]

I think the concrete screws are best for where they are intended i.e concrete.....I've used loads of them for this but I confess never in brick due to the expansion risks.
I'd consider a wider gap between wood and wall if possible, but I admit to not understanding the project fully!
John

 

[chappers]

I've cut and plugged probably many thousands of holes with a spade bit, the idea behind a tapered pellet is it gets knocked past the diameter of the hole it sits in and expands and shapes to the hole. It won't cut a clean as a router but probably as good as a screwdigger
Go for a tapered plug every time either cut yourself or off the shelf.

 

[RickH]

I've cut and plugged probably many thousands of holes with a spade bit, the idea behind a tapered pellet is it gets knocked past the diameter of the hole it sits in and expands and shapes to the hole. It won't cut a clean as a router but probably as good as a screwdigger
Go for a tapered plug every time either cut yourself or off the shelf.

Looks like I will use a Screw Digger bit ... so won't use a router. http://tinyurl.com/zxeef7h
Take the advice on tapered pellets and buy in manufactured ones... so won't bother with cutting them myself..

 

[RickH]

I think the concrete screws are best for where they are intended i.e concrete.....I've used loads of them for this but I confess never in brick due to the expansion risks.
I'd consider a wider gap between wood and wall if possible, but I admit to not understanding the project fully!
John

The wood is a cill 'top' to single brick raised beds. Around 90m of the cill to fix.
I may also put a layer of dpc on top of wall before fixing (unsure if this is good or bad idea yet)

To drill and line up the holes with plastic plugs would be a nightmare, it was my original thought. had a load of recommendations to use concrete screws .... hence went & bought them it.

Tried them out and they cut really well into brick/block.

 

[Burnerman]

I see now! A DPC will be a good thing here, and if your screws are working well then bash on.
Be lucky!
John