No padstones required?

[Andyk78]

Knockthrough, single storey extension opening up into the kitchen

Online calcs supplied as follows:

254x254x73 UC at 4.75m

250mm bearing one end and 350mm bearing at the other end, engineers description says no padstones required and to be seated directly onto the masonry, does this sound right as never heard of steel not been seated onto padstones and neither have my bricklayers?

 

[RonnyRaygun]

There must be quite a large load to the bearing if the beam is a 254UC73.

If existing brickwork I certainly wouldn't recommend bearing direct onto the masonry, even if the calcs suggest that the masonry strength is sufficient.

If the masonry is new (and the strength is sufficient) then, as long as the masonry is well built, it should not be a problem. It's not uncommon to have engineering brick pad stones rather than mass concrete.

All depends on the load per mm2 and the local capacity of the masonry.

Sound like in your case it's existing brick, so either use mass concrete pad stones or rebuild the top couple of courses with class b engineering bricks in M6 mortar.

 

[freddiemercurystwin]

250mm bearing one end and 350mm bearing at the other end

 

[tony1851]

254x254x73 UC at 4.75m

are you supporting a railway bridge or what?

If the loads are so heavy as to require a beam that size, you almost certainly need padstones.

 

[^woody^]

It looks like you've been conned with the calcs.

 

[Andyk78]

The beam is supporting the first floor and roof at back of house, the original design was a 203x203x36 I think, will check in a moment. The bco said he wanted me to go a size up as 203 will leave to much brick on either side and best to go a size up which the next is 254 hence why that size and obviously the weight goes up considerably along with it. Why is this not correct?

 

[tony1851]

The bco said he wanted me to go a size up as 203 will leave to much brick on either side and best to go a size up which the next is 254 hence why that size

What does this mean?
Is this guy really a building inspector??
With people like him around, there's no need for calculations any more!
You've struck lucky there!!

 

[Andyk78]

The double skin of brick including the cavity measure 290 inside to out so the 203 would be short either side but with 254 you are closer each side of that makes sense.
And the steel was based on the calcs provided from online structural calcs working from my drawings, these are fed into a software package I presume that pumps out the bearings and steel required although certain assumptions are made and the steel has been sizes up one accordingly by bco to suit the cavity size and both skins on brickwork so its closer to being flush to brickwork inside and out?

 

[tony1851]

A 203 wide beam can be used with padstones which straddle both skins.
You just make your padstone as wide as the wall is thick.

This is elementary stuff. Your bco seems totally inexperienced, and you are paying the price for that in having a whopping big beam.

 

[RonnyRaygun]

A 203 wide beam can be used with padstones which straddle both skins.
You just make your padstone as wide as the wall is thick.

This is elementary stuff. Your bco seems totally inexperienced, and you are paying the price for that in having a whopping big beam.

The issue might be the overhang from the edge of the beam to the edge of the masonry. I'd agree that 45mm or so overhang (plus finishes) is excessive for a 100mm wide brick. I'd agree that a 254 would be better than a 203 with a plate welded on top...

That said, the obvious solution is a pair of (guessing) 203x133 UBs bolted through with spacers.

 

[tony1851]

On older houses, the cavity wall is usually little more than 10" thick, and considering the overhang, a 203 would suffice (I would go to a maximum 1/3 overhang). But on modern (wider-cavity) walls I usually have a 250 wide plate tack-welded on.

Yes, two 203x133s would probably be easier to fix overall. But a 254/73 UC -- Jeez!!

 

[Andyk78]

I did call back about the two steels option as that's how I originally thought it would have been done, however he said he could design a 3 piece spliced steel that could be bolted but he wanted paying again for it! ! So I didn't bother. But now I have a 350kg steel to lift and place in with very limited space.....eeek!! Hope that with about me and 6 others lifting we should do it??
Better hit the gym this week and practice deadlifts!!

 

[tony1851]

he said he could design a 3 piece spliced steel that could be bolted but he wanted paying again for it!

This is often a con because some unscroupulous SEs charge you for designing a monster beam, and then charge again for the splices.
Get in some trestles, and with a few mates you should be able to get it in - just!
Good luck.

 

[freddiemercurystwin]

13 posts in and no mention of a 152x89 yet?

 

[RonnyRaygun]

Get in some trestles, and with a few mates you should be able to get it in - just!
Good luck.

Or get a Genie lift...or swap it for a pair of 152x89s