Crack in external render after RSJ fitted

[Kylemacca01]

So around late Nov last year we had a 3m bifold door fitted into an external cavity wall, a steel beam with a welded 6mm plate to carry the outer course was designed by an SE and installed above the doors, on padstones.

There is a small crack in the roughcast render right below the window at 10 o'clock to the beam, I'm 95% sure this happened when the beam was fitted. It goes between the soldiers bricks directly below the window and down about 15cm in the render. I would say it's maybe 1mm in width max. I can't see anything internally but under the window is wallpapered so would be difficult to see anyway. Windows functions without issue.

Obviously this was done 7 months ago now, I don't believe it's gotten worse but it's bothering me as I guess we are out in the garden more and using the doors daily atm. I did point it out to the building inspector when he visited (he was excellent btw) but he didn't seem concerned.

Was hoping for an opinion on what to do. My guess would be the outer course has settled slightly above the beam which has pulled down and caused a small crack in a weak point just under the window.

 

[tony1851]

Not a structural problem; all beams without exception deflect under load, and one-time cracking is not unusual. The centre of the beam has deflected the most, allowing the bulk of the masonry to pull down and sideways at the top, hence the crack in the soldiers.
Just point and forget.

 

[^woody^]

Not a structural problem; all beams without exception deflect under load, and one-time cracking is not unusual. The centre of the beam has deflected the most, allowing the bulk of the masonry to pull down and sideways at the top, hence the crack in the soldiers.
Just point and forget.

Oh, so walls are supposed to crack and its OK? I've been doing it wrong all these years.

The idea is to design a beam so that the wall above (or finishes) do not crack. And then pack the wall so that the wall above does not move.

Its no good just telling the OP to point the crack in render, when the wall behind is cracked and will just keep cracking and keep cracking the render. And water getting in will keep blowing the render.

 

[Kylemacca01]

Oh, so walls are supposed to crack and its OK? I've been doing it wrong all these years.

The idea is to design a beam so that the wall above (or finishes) do not crack. And then pack the wall so that the wall above does not move.

Its no good just telling the OP to point the crack in render, when the wall behind is cracked and will just keep cracking and keep cracking the render. And water getting in will keep blowing the render.

Why would it keep cracking if the crack is raked out and filled with mortar? Would you expect further movement? What would you suggest at this point?

 

[tony1851]

Oh, so walls are supposed to crack and its OK? I've been doing it wrong all these years.

The idea is to design a beam so that the wall above (or finishes) do not crack. And then pack the wall so that the wall above does not move.

Its no good just telling the OP to point the crack in render, when the wall behind is cracked and will just keep cracking and keep cracking the render. And water getting in will keep blowing the render.

It won't keep cracking - the deflection occurs as soon as the props are removed and any increase due to live load will be negligible.
So what deflection limit do you regard as OK for a brick cavity wall with render to prevent cracking? span/360? span/500? span/750? span/10^6.?
The SE has to make a judgement as to what is reasonable allowable deflection taking into account the condition of the wall and its materials and standard of workmanship.

 

[^woody^]

It won't keep cracking

Of course it will.

All walls will move seasonally, and once cracked, each side of the crack will move independently, any finish over the crack will re crack.

This is separate to any cracking caused by deflection - and it may well be that maximum deflection has not been achieved yet.

 

[tony1851]

As the brickwork has cracked as far up as the window cill, that tells us that pretty well all the load has been transferred to the beam.
There will be a small additional live load (eg snow load on the roof) which will cause a tiny increase in deflection, but of no practical significance.
Yes, walls move under extremes of temperature, but on this scale, I humbly and respectfully submit that any movement will be small, not cumulative, and of no consequence.
If the crack continued to get wider after each filling and each heating-up, on that basis the side wall of the house would eventually be pushed over, sometime around 2300 AD perhaps?

Imagine planet Earth as a giant sphere of cast iron. Once every century, a fly lands on the surface and then takes off again, knocking one atom of iron off the
surface. How long would it take for the Earth to be worn away?

 

[^woody^]

As the brickwork has cracked as far up as the window cill, that tells us that pretty well all the load has been transferred to the beam.
There will be a small additional live load (eg snow load on the roof) which will cause a tiny increase in deflection, but of no practical significance.
Yes, walls move under extremes of temperature, but on this scale, I humbly and respectfully submit that any movement will be small, not cumulative, and of no consequence.
If the crack continued to get wider after each filling and each heating-up, on that basis the side wall of the house would eventually be pushed over, sometime around 2300 AD perhaps?

Imagine planet Earth as a giant sphere of cast iron. Once every century, a fly lands on the surface and then takes off again, knocking one atom of iron off the
surface. How long would it take for the Earth to be worn away?

If you think back to your lessons on masonry movement you will recall that there is movement due to loads and movement due to other factors.

You are concentrating on deflection loads, and assuming that they are now complete, but you are forgetting seasonal expansion and contraction of the panel, plus any freezing of moisture that gets into the cracked render.

The seasonal movement may not be cumulative but it will be regular and may wil be progressive. It will also be random due to influence from extreme weather, say the next dry winter and hot spring.