RSJs not quite level, acceptable tolerances?

[Smellypunks]

We are in the process of having the chimney removed. So the builders have just put in two RSJs (152x152x23-5350mm). They sit on engineering bricks and steel plates at both ends. One end was chamfered to fit the roofline. The RSJs sit on 10mm steel plates at the roof side and 15mm plates at the chimney end.

Structural engineers report said:-
For purposes of beam bearings conservatively 5N/mm2 bricks in 1:2:9 mortar has been assumed (0.42N/mm2 allowable bearing stress - unfactored) although Fletton brickwork is in place. At the flank wall to avoid the beam protruding through the roof the end will be chamfered.
Bearing R1: 10 mm m.s. bearing plate, size 175 x 100 mm

Now all looks ok bar two small things.
- One there is only 80mm of RSJ on the bearing at the roof side. Note the builder will be moving the plate on Monday so it covers the full brick but that will only be 80mm.
- Two both of the RSJs are not quite level maybe out by 2mm per meter at a guess so maybe 10-12mm over the 5.3 meter length.

See photos.
Are these acceptable tolerances? Building control is coming on Tuesday.

 

[kp00110]

I can't imagine any problem with 10mm out of level for a hidden beam especially. Plus it's spliced in situ so dofficult to get such a beam perfectly level as the splice will always add a small misalignment between the beams either side of splice

 

[^woody^]

How accurate is your small level over 5.3m?

I'd be more concerned about the bearing and the chamfer, and ask the engineer if it conforms with his design.

 

[Smellypunks]

Thanks both.

Well I only used a 1m level and put a small 2mm wedge under it and that made it level. I assumed that 2mm per meter over the 5m span.

I will email the engineer and see if he would be happy with the 80mm bearings.

 

[freddiemercurystwin]

Use a water level if you really want to know. NHBC level tolerance for floors is 3mm/m for up to 6m span.

 

[kp00110]

I'm sure would be fine considering what was usually the norm with gallows brackets but yes best checked

 

[tony1851]

Out of level by that much not an issue. Neither is 80mm bearing - chimney loads are actually quite small, relatively speaking, due to the bonding of the brickwork.
Nice splices btw. Hopefully they supplied the correct grade of bolts?

 

[kingandy2nd]

Out of level by that much not an issue. Neither is 80mm bearing - chimney loads are actually quite small, relatively speaking, due to the bonding of the brickwork.
Nice splices btw. Hopefully they supplied the correct grade of bolts?

Nothing to do with the thread, but very happy to see you back Tony. I was worried about you.

 

[^woody^]

Neither is 80mm bearing -

Even with a chamfer?

Surely the bearing stress would have something to say about it?

 

[Smellypunks]

freddiemercurystwin - thanks good to know NHBC level tolerance for floors is 3mm/m for up to 6m span.

tony1851 - today it is the chimney but who knows in years to come we might want to convert the loft adding more weight. So would prefer it was done correctly now.

kp00110 - I was sure gallows brackets would be used before we started this project but the engineer said that because the next-door neighbour has removed their chimney that we needed all this steel. Seems overkill but them the rules!

Woody - the chamfer does not go to zero, they left an inch before starting the chamfer which I was quite happy to see.

 

[^woody^]

Woody - the chamfer does not go to zero, they left an inch before starting the chamfer which I was quite happy to see.

Was the chamfer designed by the engineer? And is the chamfer in accordance with the design?

 

[Dereekoo]

Sometimes they say the obvious is to obvious but I am at a loss to understand what these 2 beams are supporting. You say you are having the chimney removed so what's left to support, unless you mean the lower chimney breast is being removed and the chimney is remaining and these 2 beams support the chimney side walls and they will have a cross beam to support the chimney front wall?

 

[robinbanks]

Seems a bit lacking in insulation now, in the areas around the steels..

 

[Dereekoo]

Even with a chamfer?

Surely the bearing stress would have something to say about it?

Is it not like a bow string railway bridge with stresses at the edges so much reduced that so can be the amount of steel?

 

[^woody^]

Is it not like a bow string railway bridge with stresses at the edges so much reduced that so can be the amount of steel?

The point is that when calculation was done, that is based on a the full section shape of the beam. So if that section is then cut at instalation and no longer exists, the calculations are no longer valid. So it's important to know whether the engineer has designed the bearing with that exact chamfer.