Is this RSJ long enough

[markc]

Intumescent paint has to be thick to get the film thickness as it works be swelling up when exposed to heat. The can or spec sheet should give you the applied thickness to be effective, usually 400 microns (0.4mm) and upwards. 

Edited June 27, 2023 by markc

[saveasteading]

12 minutes ago, Conor said:

don't water down, I'd be tempted to water down the first coat regardless.

It removes the way the paint works. It has to be thick.  Yes it's horrible but don't thin it.

 

Assuming these are planks. They sit on the steel and protect it. Any tiny gaps (mm) are irrelevant and don't need protection. So the top surfaces are fine left raw.

 

I haven't met a bco yet who made any attempt to measure or assess thickness. Or even count empty cans. I assume they don't understand it Plus don't want any blame after a fire.

[Mr Blobby]

2 hours ago, saveasteading said:

 

3 hours ago, Mr Blobby said:

I have a choice of paint or paint.   

Surprised to hear that. Why? Who Says? 

 

 

Architect and builder say so because I'm doing it so it costs them nowt.

 

There is a lot of painting to do though.  Builder says do it after the hollow core slabs are in place but before then sounds more logical as @Conor says.

 

Our BCO is allegedly easygoing on this.

Any tips on the painting to make my life any easier?

What's the sealing coat?

Edited June 27, 2023 by Mr Blobby

[saveasteading]

2 minutes ago, Mr Blobby said:

Any tips on the painting to

Don't paint where it doesn't need it. If you're being told to paint where the beams are already going to be  protected then I worry how (if) they have calculated it.

 

It's thick and gooey. So needs  a hefty brush, like a wallpaper brush. You can use a roller.  I think a small foam one will be best.

The seal coat is easiest because of the ccolour. I assume white.

 

Perhaps I'm interfering soignore and do what you're told if you prefer. It's your effort and money.

It's just I have seen so much done wrong...whether underdone (too thin paint) or overdone (intumescent because its technical, where a sheet or 2  of plasterboard is enough, or is even  already there.

 

Do you have calculations based on the steel sections?

 

But will these beams be on show? 

A steel needs to get to about 300°C to fail. Where will  that fuel be coming from? Isn't there a ceiling?

 

Unless of course you are packing the void with kindling and polystyrene, with a hot light bulb in the middle of it, then leaving holes in the ceiling for ventilation.

 

 

 

[Big Jimbo]

The only time i used it was for a stage set that i made for a production about 30 years ago. I gave the manufacturer (Bolloms i think) the total surface area, and they supplied me with the paint. Loads of it and it cost a fortune. They also provided me with the Fire cert that was required for the production company.  It was hideous stuff to paint. I used loads of brushes, rollers etc. To be honest, i didn't use it all because i had lost the will to live.

The only other time i used it was when i did a loft conversion, and because i had it, used it.  When the building inspector came he said what was i covering it with. I told him, One layer of 12.5 mm plasterboard. As he said, i shouldn't have bothered. By the time the fire got through the plasterboard, and heated the steel to the point that it failed, we would all have been rescued hours before, or long dead.

I swore that i would never use the bloody stuff again. You have a lot of steels. That is not going to be fun.

[saveasteading]

20 minutes ago, Big Jimbo said:

By the time the fire got through the plasterboard,

plasterboard works so well, because it isn't only a physical barrier. When it gets super heated, the chemistry changes and the bonded water is driven out, especially at all the edges, then turns to steam, taking energy out of the fire.

 

we have all thrown a bit on the fire to see what happens, haven't we. ? not a lot happens.

 

26 minutes ago, Big Jimbo said:

the manufacturer (Bolloms i think) provided me with the Fire cert

If I recall it only confirms that you bought x litres of their paint.

 

A painter once told me proudly he had managed to only use half the paint we had supplied, albeit with strict instructions.

[Alan Ambrose]

Of course, it's not how long your RSJ is, it's how you use it...

[Mr Blobby]

Structural Engineer has got back to me about this RSJ (and some other things hence the delay).

He says the bearing is "a bit short".  He says it works in calculation at 210mm but if replacing the steel then he advises 250mm bearing to give some additional capacity.

He has suggested an alternative to replacing the RSJ may be to weld a piece on at the end.

 

Glad I checked this🧐

[saveasteading]

20 minutes ago, Mr Blobby said:

weld a piece on at the end.

A very heavy piece, or it will just bend. I think SE should be telling you this.eg what thickness of plate and what weld.

 

Good to get an answer though.

Edited June 28, 2023 by saveasteading

[Mr Blobby]

1 minute ago, saveasteading said:

A very heavy piece, or it will just bend. I think SE should be telling you this.eg what thickness of plate and what weld.

 

I'd assumed the same cross section as the one installed.  I'll ask...

[Mr Blobby]

 

On 27/06/2023 at 18:12, saveasteading said:

Do you have calculations based on the steel sections?

 

Yes, the paint company had the steels plan and calulated the required quantity.

 

 

On 27/06/2023 at 18:12, saveasteading said:

But will these beams be on show? 

No

 

On 27/06/2023 at 18:12, saveasteading said:

 

A steel needs to get to about 300°C to fail. Where will  that fuel be coming from? Isn't there a ceiling?

I agree, I think the paint is probably a waste of time but building control like to see it.

 

..Painting wasn't as bad as I expected.  But then after reading all the comments here, I was expecting it to be hellish. 😬 

Yes its thick and hard work but my builder actually pitched in to halve the pain.  Which was nice of him.

 

And here's the finished beam, with a bit welded on to take it over the middle of the padstone and beautifully painted. 🤗

 

 

 

[saveasteading]

So it's done and looks good. The ceilng woild probably have done the job, but youre right that the bco will favour the paint.

 

How many voats was that? Have you applied  the same manufacturer's seal coat? 

[jon-lee]

On 26/06/2023 at 18:47, ETC said:

Look at the specification on your SE drawing. You won’t get an answer here.

 

On 26/06/2023 at 17:11, Mr Blobby said:

I think steel beam marked with 2300 should be longer so that it is supported by more of the padstone.

Should I get it swapped out?

 

 

 

 

in most design there's no right or wrong providing it structurally stable. IMO the bearing is more that adequate. What id be concerned about is steel to the left bearing onto it as the pic shows that the far left steel is cantilevered by a pinned connection (im assuming that blockwork will be built up to support??) personally id of extended the 2300 beam to support the far end beam but thats just me  

Edited July 23, 2023 by jack
Moved text out of quote

[Mr Blobby]

18 hours ago, saveasteading said:

 

How many voats was that? Have you applied  the same manufacturer's seal coat? 

 

One coat.  My builder laughed when I asked if it needed a second coat.  On the tin it said the sealant was optional.  AFAIAA the BCO has never questioned the paint, as long as he can see it.

 

10 hours ago, jon-lee said:

What id be concerned about is steel to the left bearing onto it as the pic shows that the far left steel is cantilevered by a pinned connection (im assuming that blockwork will be built up to support??)

 

I'd be concerned about that beam being cantilevered too!  I can see that's how it looks from the picture above, with a body hiding the detail.

 

This picture shows it better, witht the steel supported, taken from a differnent angle:

 

 

 

Edited July 23, 2023 by Mr Blobby

[saveasteading]

3 hours ago, Mr Blobby said:

My builder laughed when I asked if it needed a second coat.

OK, so it's not going to fail in fire. My original point here was that it may not need any coating.

 

But the builder laughing isn't great. The same one who fitted the beam?

 

The amount of paint required is usually measurably thick, such that most people choose an alternative, or ignore the instructions.

I have never known a bco check the thickness physically or by counting tins, so I  think this is deliberately avoiding responsibility.

 

If you have any paint left, it is fun to apply it elsewhere and low torch it.

 

That's the first time I've heard of the seal coat being optional, that is quite an advantage. What brand is it?

[Mr Blobby]

5 hours ago, saveasteading said:

That's the first time I've heard of the seal coat being optional, that is quite an advantage. What brand is it?

 

This stuff I think. https://www.rawlinspaints.com/home/fire-retardant-paints/steel-intumescent-paint/5227-thermoguard-thermocoat-wi-ultimate.html

 

The tin is in the wheelie bin. I'll go and check when back on site on Tuesday.

[Mr Blobby]

On 23/07/2023 at 17:23, saveasteading said:

That's the first time I've heard of the seal coat being optional, that is quite an advantage. What brand is it?

 

Here's that paint tin.  It says the sealer is optional if the beams are in dry concealed conditions.  They will be dry at some point, but not during construction. 

 

 

[Mr Punter]

Yes that intumescent paint is horrible stuff.  Goes yellow and seems to encourage rust.