Are these block 7.3N or 10N?

[iMCaan]

Hi all

 

I ordered 10N concrete blocks. However, it's stated 7.3N on the delivered concrete blocks.

I contacted the building merchant and their supplier states, "our 100mm 7n concrete paintgrade are manufactured to 10.5n strength". 

 

I'm going with ground and first floor block and beam floor. Would 7.3n concrete blocks be sufficient to take weight of the block and beam floors?

 

Any advise highly appreciated.

 

iMCaan

[nod]

7n would be fine to put a block of flats on 

[Gus Potter]

Hello iMCann.

 

Unfortunately there are at least a couple of other things to consider. Generally a wall of 7.0N (Newtons / mm^2 compressive unit strength i.e each individual block) can carry a surprising amount of vertical load if the wall is loaded about it's centreline and not subject to other sideways forces.

 

But beam and block flooring can introduce quite high local stresses where the beams rest on the blocks, an over stress can lead to local crushing of the block.

 

The walls may also be designed to resist horizontal wind loads which cause bending (flexure) in the wall.

 

Even internal walls are subject to wind load! Imagine you have a big set of sliding doors open and a gust of wind blows in.. it can load the internal walls sideways. It's usually not a problem on domestic houses but on large industrial buildings or houses with two storeys and a vaulted ceiling this "internal wind loading" needs checked.

 

The flexural stength of the wall is partly dictated by the unit strength of the blocks. The higher the block stength generally the stronger (up to a point) the wall in flexure.

 

I would err on the safe side and check first with your SE. Seems odd though that an SE would spec 10N blocks when 7.3 would have done. At the same time ask your SE  how to phrase the question (so they don't give you the run around) to the supplier so you can ascertain the strength of the block if 10N are indeed required with some evidence to back up any claim they may make, even though the blocks are stamped 7.3N.

 

 

[iMCaan]

Thank you nod.

Thank you Gus potter for a very detailed reply. 

 

I don't have a SE.

 

I thought 10N blocks would be better up to first floor. Just for a piece of mind,

 

Above first floor would be 7.3N blocks.

 

 

[Gus Potter]

4 minutes ago, iMCaan said:

I don't have a SE

Please be safe.

 

You are building two storeys so odd / unexpected / bad things can start to happen and you have higher loads than say single storey.

 

If you need to ask about the block strength then you don't have sufficient experience in structural design to make sure what you are doing is safe.. and be able to prove it now / later if you need to sell. Sorry to be blunt.

 

What about running this by say an SE, they may be able to say..  hey you can save money here as you are over designing, but here you need to up your game. Ideally an SE / experienced designer should be able to save you more than their fee in the round?

 

 

 

 

[Temp]

Our SE specified 14N blocks in some highly loaded places. 

 

[iMCaan]

Gus Potter you are right. Will try to get some advise from SE.

Thanks. 

[Gus Potter]

31 minutes ago, iMCaan said:

Gus Potter you are right. Will try to get some advise from SE.

Thanks. 

All the best, make a list and pick their brains, offer to pay a bit more for the advise.. is goes down well. From an SE point of view it's often easier to spend half an hour or so chewing the fat with a Client than going through the process of invoicing, also a satisfied Client may just recommend you to their friends!

[Annker]

"our 100mm 7n concrete paintgrade are manufactured to 10.5n strength".

^Could get a job as a script writer for a politician I know?

[iMCaan]

Thank you all.