bricks

[Stephen]

Hello,

Are bricks frost proof and water proof only on the outside? If the face of one gets chipped, does that mean it becomes susceptible to water ingress or frost damage? I was told this but don't know if it is true.

I have a brick with a damaged face and I wonder whether I should replace it? I also see chipped ones on the shelf at Wickes and wonder whether they can be used or whether they have been left behind by other customers on purpose!

On another brick topic: is an engineering brick different to any other brick or is the only difference that the engineering brick is plain in appearance?

Thanks, Stephen.

[Nightjar]

Bricks are not waterproof. That is why cavity walls were introduced - to stop water soaking right through the wall. The rate at which they absorb water can affect the bond strength of the mortar.

Not all bricks are frost resistant either. There are three categories: Frost resistant - resistant to repeated freezing and thawing when saturated; Moderately Frost Resistant - durable except when saturated and subject to repeated freezing and thawing; Not Frost Resistant - only for use indoors or under an impermeable cladding. If they are frost resistant, minor damage will not affect that.

More trouble than it is worth, unless you are offended by the appearance.

I wouldn't use them anywhere they can be seen.

Engineering bricks are denser and stronger. They also absorb less water. Blue engineering bricks are Class A - 70 N/mm2 and 4.5% water absorption. Red engineering bricks are Class B - 50 N/mm2 and 7%. This makes them more suitable for use in foundations.

For facing bricks, the minimum strength is 5 N/mm2 (although they can be made in different strengths, in which case they mus be at least as strong as the manufacturer says) and there is no set limit for water absorption.

These figures are from BS 3921. Standard BS EN 771-1 gives different compressive strength figures, because it uses a different test method.

Colin Bignell

[Skipweasel]

They're fired at a higher temperature, which makes them less absorbant and harder. You can tell by the almost ringing tone when you strike them.

[The Natural Philosopher]

Not necessarily.

How vulnerable a brick, or indeed a bit of concrete or render is, to frost damage is partly its porosity that allows water in (or not) and partly its mechanical strength that resists spallation (or not).

Composition is probably more important than the minor variations that happen due the the outside being a bit better 'cooked' than the inside.

No, It's got a different composition, and probably is fired at a higher temperature.

Its different all the way through,as you would know if you had ever taken a cold chisel or an angle grinder to one.

[Tabby]

with some bricks yes, some no. Old soft bricks are very susceptible once the face is gone.

You could wait until it disintegrates in 10 years, or replace now.

Harder, less absorbent, good for underground use.

NT

[The Medway Handyman]

Or when you try to drill them :-)