Water absorption for facing bricks %

[Ruggers]

Can anyone answer what I should be looking for when choosing a facing brick for the exterior walls of a house. I have seen 3 bricks, all F2 but they range from 7%, 10%, 19%.

Living in the lake district it does get very wet at times and cold winters so I was concerned higher absorption would lead to frost damage?

I came across this quote:
Many people would think that an absorbent brick would be likely to suffer from frost. The BDA did state there is no connection between the 2.
Also a less absorbent brick can allow more water penetration into the cavity (known as the Raincoat/Overcoat effect)

 

[stuart45]

The overcoat/raincoat effect is that a more absorbent brick soaks evenly in more of the rain and lets it evaporate out again , whereas a less absorbent one lets it run down the wall and in through any cracks in the mortar and into the cavity.
It's more of an issue with a solid wall where hard engineering type bricks were found to perform worse than softer bricks.

 

[Ruggers]

So is a 7-10 or 19% brick suitable for a colder wetter climate, the 19% one was my colour preference.
Apart from the frost concern of them holding water and freezing, I was thinking they might attract more moss/algae if they absorbed more water?

 

[stuart45]

As long as it's F2 rated it will be OK.

 

[^woody^]

The absorption % is more to do with how much suction the brick has and will impact the initial bond with the mortar, not how much it absorbs in use.

IIRC 20% is the maximum for a clay brick, and all it means is that those at the top end are really dry and will suck like a Newcastle lass after a few pints.

10% or so for engineers so a stronger bond.

 

[Ruggers]

The absorption % is more to do with how much suction the brick has and will impact the initial bond with the mortar, not how much it absorbs in use.

IIRC 20% is the maximum for a clay brick, and all it means is that those at the top end are really dry and will suck like a Newcastle lass after a few pints.

10% or so for engineers so a stronger bond.

Nice reference ha.

I'll get some samples an prices then if all are suitable within the 7 to 19 range.
Are you saying the 10% will bond better but all will be as strong as each other?

 

[^woody^]

It doesn't necessarily mean that lower absorption will bond better, rather that the risk is greater of poorer bonding due to rapid removal of water.

So say, laying the bricks in winter will not be the same as in summer, and if you know that you can take precautions - like you would with that Newcastle lass.

 

[Ruggers]

I just had a look at a brick ive used a lot of at home and its 16%, i recall doing some of them with the builder on a hot day with normal sand and white cement having to dip them in water because they were pulling the moisture from the cement.

We then left it until a cooler day. So the 7% bricks would of caused less of a problem i presume.