Does a RSJ always require a padstone?

[Jason1971]

What is the latest regs for installing an RSJ. I had a knock-through last year, paid the SE for calcs, paid the builder to install, and paid the LA to pass it. Job done.
I went to a friends house when their builder was installing the 2xRSJ on their knock-through. I noticed he had used an old block from the knockdown wall as a padstone! The opening is the outside wall (block and brick) joining the garage/utility to the main kitchen. Above the RSJ is second floor then the apex of the side of the house. (alot of brickwork). The 2xRSJ are at least 2.5m long.
Are there any circumstances when a padstone is not required? Thanks

 

[^woody^]

The requirement its that whatever the beam is bearing on needs to be able to take the load, not that a padstone must be used

 

[Jason1971]

Hi Woody, Most houses are brick and block so when would you ever need to use a padstone?

 

[^woody^]

If the concentrated load from the beam at the bearing was too great for the brick or block, then something else would be needed - a padstone or a stronger brick/block etc

 

[Jason1971]

Which is where the calculations come into it I suppose. The LA inspector is coming this wednesday. Is he qualified to judge whether the blocks are sufficient. As the SE is the builders pal.
I know I appear very cynical, but the kitchen refit is high-end finish, and there are some cowboys out there.
If you google RSJ, you always see comments/instructions about also fitting padstones. I can't get out of my head the fact that this RSJ is holding up the side of the house (2nd floor) and the triangular roof section of bricks.(gable end I think it's called) If that weight doesn't require a padstone I don't know what does.

 

[Jason1971]

Addition to the note above.
I understand about the calcs.
Lets say a padstone was required as the load was too great.
The padstone then sits on-top of the original pillar blockwork, surely that block can't take the load either. Do you know what I mean?

 

[tony1851]

If a padstone is necessary, it will be larger in surface area than the underside of the steels which rest directly on the wall.
For example, if the 2 steels are each 4" wide and sit, say, 6" into the wall, the total contact area would be 48 sq in..
A padstone would be necessary if the stress (pressure) on the brick/block on that 48sq.in. immediately below the steel was too much for the brick or block to the point where it would cause local crushing.
The padstone would be designed to have a larger contact area than the underside of the steels, so it will spread the load over a larger area of brick/block and so reduce the stress.
As Woody has in effect pointed out, if the load on the beams is not great, or
if the existing brickwork/blockwork is high-strength, a padstone may not be necessary.

 

[^woody^]

The bizarre thing is, and I have never been able to work this out, but if you use a lintel, the BCO wont bat an eyelid if it rests directly on a wall.

But if you use a steel beam in exactly the same situation, then the BCO will invariably want calculations for the bearing or a padstone to be fitted

 

[Jason1971]

Thanks both..
So Woody, with your last comment are the BCO qualified to check the maths on the calcs to determine whether an RSJ is required? Excuse my ingnorance, but are the BCO the Local Authority planning inspector?

 

[Jason1971]

Another observation with the RSJ..
The RSJ that supported the block work(not the brick work) was thinner than the block work itself by about 1/2" to 1" both sides.

 

[tony1851]

(Jason, I was waiting to see if Woody would answer your last questions but he's probably having his tea at the moment, so here's my 2 cents worth!).

The Building Inspector wil probably not be qualified to look at the calcs to check regarding a padstone. This job is usually done by the Council's engineer, though you probably won't get a quick answer back from them. Remember that they won't do the calcs for you, they will only check the figures you provide.

No, the BCO is nothing to do with Planning - he is only concerned with building construction matters.
Re your 2nd post. If the flange of the beam is thinner than the blockwork, it's probably a 6" x 3 1/2" RSJ.

 

[^woody^]

Some BCO's (Building Control Officer or " building inspector'") are able/qualified to check calcs, but most depts have a dedicated structural engineer to do this, or else sub the checking out to a private firm. Its a liability issue in case of complaints later on.

A planning officer is not a BCO - they tend to lack the common sense required of a BCO

There is a massive amount of knowledge and experience within the dept's and all experienced BCO's should be able to tell at a glance that a beam of certain dimensions, and a certain padstone or brick or block will be adequate.

Some councils even produce a 'ready reckoner' covering all situations up to a certain sizes, so calcs are not required if a given beam is used

Beams don't need to be as wide as the wall above ... within reason

 

[Jason1971]

Called my pal, and yes you're right with the dimensions. Also the blockwork overhung by 1/4" either side not what I said before.
Does the Council engineer always check the dimensions or is it left that the SE knows what he is doing?
How can I get the calcs rechecked? How do the BCO know what crush load factor thingy is being used for the calculations?

 

[^woody^]

The BCO will check that the beam is of the same dimensions specified

The factor for the bearing capacity of the masonry is within the calculations - again the BCO will check what is there now, and would normally reference this against known bearing capacities for any given material

In practice, the council engineer validates the calculations and makes a note to the effect of "this is OK without a padstone as long as the wall is made of 'x' masonry". The BCO will then just check that the wall is made of 'x' masonry or better

 

[Jason1971]

So the BCO is/should be qualified to determine the padstone requirement.
Wednesday is D-day, I'll let you know what happens.
It looks like the builder/SE has used to bare minimun regarding regs, he overhung the RSJ 6" into the wall and 12" the otherside. I believe 8" or 9" is recommended.
Thanks Lads, you've been a great help.

How do I 'thank-you'? You know.. so and so has been thanked!!!! How do I do it? Don't bother... just found it...... Divvy