Thickness of mortar around bricks

[Windmill]

If I'm drilling through some material so as to insert a wallplug, and am lucky enough to hit solid brick rather than the softer mortar between bricks (which of course is invisible under a plaster or render surface), how far away vertically and horizontally should I drill the next hole so as to have the best chance of finding brick a second time?

It obviously depends on whether new and old bricks have always been the same size and on the thickness of the mortar at the sides and above and below each brick.

Occasionally it almost seems as if there's more mortar than brick, which is annoying if I want a fixing to be as strong as possible.

[Martin Bonner]

A multiple of the brick spacing. You may be able to find that out by looking outside. Otherwise, just pray.

[Harry Bloomfield]

Windmill used his keyboard to write :

An inch away from your original hole should be enough. Vertical joints are less than half the size of horizontal ones, so you would have a better chance of brick if you move 1" up or down. If you then hit a joint again, you know you are in line with a vertical joint.

Another strategy, perhaps with a better chance of success, would be to drill 1" away, but at a 45 degree angle from your first hole.

[Nightjar]

Bricks have been much the same size since brick making machines were introduced during the industrial revolution. Today the standard is expressed as 65mm high x 102.5mm wide x 215mm long, with a 10mm mortar joint, or, as specified by Parliament in the 18th century, 2.5 inches x

4 inches x 8.5 inches with a 3/8 inch mortar joint.

Colin Bignell

[The Medway Handyman]

The chances of hitting a joint are fairly low I would think, given the area of the brick compared to the area of mortar. If fixing a bracket or similar, the spacing of the holes determines the position anyway.

Also, if the bracket or whatever has 4 holes & you get proper fixings in

3, it ain't gonna fall off :-)

So, use Rawlplug UNO plugs which work well in pretty much anything, or resin anchors for a really heavy load.

[PeterC]

Far worse - and seems Sod's-Law frequency - is hitting the edge or corner of a brick. I once drilled a hole (10mm pilot; 25mm final) from inside, started half way up a brick and caught the bottom edge of an outside brick. This put a near 'step' in the hole and took another half hour to get it to take 25mm conduit (I know - but 25mm was the biggest bit that I had at the time).

[Windmill]

That sounds like what I wanted to know; if I have found what seems to be solid brick for one hole, another hole 2.5 + 3/8 = 2-7/8 inches up, or 4-3/8 inches away horizontally _should_ also find solid brick. Hopefully. I'm talking, of course about a situation where I have some choice when positioning the second hole, which isn't always the case.

It also tells me that if when drilling the first hole I've found mortar rather than brick, and am able to ignore/plug up that hole and try for another and better first hole, my best bet for the next attempt would be to move half those distances away. That ought to be in the middle of a brick. Aren't bricks usually staggered half a brick's length in successive layers? Which would also need to be taken into account.

All much simpler when you are able to actually see the bricks!

[Windmill]

I would have thought so too. Yet there have been times.........

If the first hole seems to have gone into soft mortar, I'm usually tempted to abandon it and try again some small distance away (when that's possible, of course).

That's what I think, in most cases. But I get nervous about things like our 100 mph winds and a satellite dish on top of a 3 story building.

Long ago I read descriptions of the procedure for using resin anchors, but have never actually used them. Are they even a possibility, on the vertical side of a chimney stack? Doesn't the resin have to be poured in from the top?

What's this 'epoxy mortar' stuff? Any help in such a situation?

[The Natural Philosopher]

I've always been far happier to find mortar, than brick. filling holes with car body filler and then inserting the plug (or using body filler as the plug itself) is a much sounder solution IME.

sometimes. Sometimes not. edpends on the bricklayer and the purpose.

or concrete blocks, or lightweight insulating blocks, or generic bits of rubble or whatever the wall is ACTUALLY made of.

[The Natural Philosopher]

resin anchors are probably car body filler. epoxy mortar is similar, but less good at being drilled into.

The art of using CBF is to make a big hole, in many ways the more irregular the better, for grip, and fill it full of car body filler.

before it sets, stick a rod in it to make a hole where the fixing is going to go, or drill it once set.

Then if its BIG hole,. topfill it with decorative mortar or whatever.

a decent screw in it will be stronger than the wall its attached to.

[Nightjar]

On 08/05/2013 04:28, Windmill wrote: ...

If it is a brick built cavity wall, probably. That is known as stretcher bond. There are alternatives, particularly if the wall is solid brick.

Colin Bignell