Minimum mortar strength needed to satisfy building inspector

[desperateofderby]

Building inspector has just been round & it turns out that the builder who knocked thru' our kitchen/diner has not sat the RSJ on a "padstone" (engineering bricks would suffice according to the inspector) as per the engineer's specification.

The stress under the beam is very low = 0.66 N/mm2

My husband is a civil engineer, but does not deal with domestic materials.

He reckons that it could be reasoned that the steel beam bearing on a suitable mortar layer will be sufficient. Whilst we do not know exactly how strong average building mortar should be, we think it should be stronger than 1MPa?

 

[Architexeter]

Speak to the engineer who did the original calcs and let them know the end bearing "as built" so that he can accurately work things out.

The padstone does two thing, it has the compressive strength but also a large enough footprint to pass the load below onto a larger area. Would the motar as you propose do both?

 

[tony1851]

If hubby is an engineer, surely he would know where to look this up?

 

[desperateofderby]

He tells me that such information does not come cheap (and we are already facing considerable expense here).

He deals with large infrastructure, not domestic, so the specs will differ.

 

[Architexeter]

Would it be possible to retrospectively put in some engineering bricks/padstones?

 

[desperateofderby]

I am hoping that if that becomes necessary, it will be possible without having to dismantle fitted kitchen units.

To quote one of my husband's favourite sayings, "We can build anything you like, anywhere you like.... it's a matter of how much you are willing to pay for it."

 

[tony1851]

He tells me that such information does not come cheap

Thought it was just in any basic book on masonry - it's elementary stuff really.

 

[Static]

Class iv mortar (which is about as poor as it gets) is about 2N/mm2, but the calc for bearing takes the combined block or brick and mortar class into account.. that said even a 2.9N block on class iv mortar can achieve 1.4N/mm2

Just get a bearing calc done to prove the wall fine.. tell your husband to run through BS5628-1 or pay someone else to prove the bearing is adequate for building control.

 

[jeds]

At that sort of loading a padstone is unnecessary. Engineering brick is fine.

 

[desperateofderby]

That's what the building inspector suggested.