Is a Class B engineering brick the same as a Category 30 engineering brick?

[Adsibob]

Sorry for the stupid question, but structural drawings are specifying Class B and the brick colour I have found which works with my scheme is available as a Category 30 or 50. So I'm confused.

[Temp]

My understanding is that Class 30 or 50 refers to the compressive strength of 30 or 50 N/mm^2 (Newtons per square mm). 

 

According to this Class B engineering  bricks need a compressive strength of at least 75 N/mm^2 so Class 30 and 50 don't meet Class B..

 

 

https://www.wienerberger.co.uk/tips-and-advice/brickwork/how-can-i-identify-different-types-of-bricks.html#:~:text=Class B engineering bricks have,red and blue engineering bricks.

 

Quote

Engineering bricks are rated as Class A or Class B, with Class A being the strongest but Class B being more common.  Class A engineering bricks have a compressive strength greater than 125N/mm² and water absorption less than 4.5%. Class B engineering bricks have a compressive strength greater than 75N/mm² and water absorption less than 7%.
 

 

Engineering bricks are normally hidden away in piers or foundations so perhaps go back to your SE if you are having problems finding the right colour. See if he can't design them out or hide them or agree 50N/mm^2 is ok. They should have a frost rating as well.

 

I also recommend choosing bricks with low effervescence to minimise white salt deposits on visible bricks.

 

Edited February 1, 2021 by Temp

[Adsibob]

33 minutes ago, Temp said:

My understanding is that Class 30 or 50 refers to the compressive strength of 30 or 50 N/mm^2 (Newtons per square mm). 

 

According to this Class B engineering  bricks need a compressive strength of at least 75 N/mm^2 so Class 30 and 50 don't meet Class B..

 

 

https://www.wienerberger.co.uk/tips-and-advice/brickwork/how-can-i-identify-different-types-of-bricks.html#:~:text=Class B engineering bricks have,red and blue engineering bricks.

 

 

Engineering bricks are normally hidden away in piers or foundations so perhaps go back to your SE if you are having problems finding the right colour. See if he can't design them out or hide them or agree 50N/mm^2 is ok. They should have a frost rating as well.

 

I also recommend choosing bricks with low effervescence to minimise white salt deposits on visible bricks.

 

Thanks @Temp I also thought that engineering bricks weren't usually visible; but in discussing it with the builder today he said that the DPC is 6 inches above ground level and that all bricks beneath the DPC should be engineering bricks. Looking at the engineer's drawings, that is consistent. But I'm having a french drain filled with pea shingle around the perimeter of the property, so I would have though those 6 inches will be covered with pea shingle. We started building 3 weeks ago and it's only over the course of those last three weeks that I've come to realise that our plans weren't detailed enough...

[tonyshouse]

Any stock brick (frost resistant) will do the job. 

[PeterW]

Class B are available in red or blue, commonly called Staffordshire blues. They are used below DPC for a number of reasons including being near impervious to water and very strong under frost damage situations. 
 

Category 30/50 are ordinary bricks with higher strength - I doubt they meet the frost damage level of a Class B. You will only see 2 courses at most so I would just get the closest Class B to your scheme in red. Just check manufacturers as they do look slightly different colours between factory locations. 

[Temp]

We have engineering bricks below ground but regular (frost resistant) bricks everywhere else inc between ground and DPC.

 

 

[Temp]

51 minutes ago, Adsibob said:

the DPC is 6 inches above ground level.... snip.. but I'm having a french drain filled with pea shingle around the perimeter of the property, so I would have though those 6 inches will be covered with pea shingle

 

No.  The DPC is normally 150mm /6"normally above ground even if the ground is actually a French drain full of pea shingle.

 

 

[Adsibob]

8 minutes ago, Temp said:

 

No.  The DPC is normally 150mm /6"normally above ground even if the ground is actually a French drain full of pea shingle.

 

 

okay, thanks. What about covering the bricks in between ground level and the dpc with some form of damp proof render/cement?

[Temp]

You can render below DPC (just check with the render manufacturer as not all approve their products for that). Personally I would just find frost resistant bricks. 

 

Edit: I'm not sure if you can render all engineering bricks as some are slightly glossy? Would render bond well to those?

Edited February 1, 2021 by Temp

[Adsibob]

7 minutes ago, Temp said:

You can render below DPC (just check with the render manufacturer as not all approve their products for that). Personally I would just find frost resistant bricks. 

 

Edit: I'm not sure if you can render all engineering bricks as some are slightly glossy? Would render bond well to those?

The facing bricks we are using are "fully frost resistant" apparently, but the engineer has specified engineering bricks below the DPC. It's a two storey extension, so needs to take quite a lot of weight.

[Temp]

I'd go back to the SE and ask if you can use engineering bricks below ground and regular/class 50 between ground and DPC. 

 

Our house is also two storey. 

 

 

Edited February 1, 2021 by Temp

[Ian]

@Adsibob

Any grade F2 (frost proof) brick below DPC should be acceptable to the engineer. You’re not building a railway viaduct so I’d be very surprised if the engineer specified engineering bricks because of their high strength - it’s probably just because that’s what is often used below DPC level.