Intumescent paint over blackjack.

[paro]

Hi All - This is my first post (though I probably should have starting posting here when I started my extension). I've just been searching through my BR drawings for something unrelated and came across statement on steelwork stating that all steelwork should be coated in water based intumescent paint to provide 30 mins protection.   

 

In and of itself I would have had no issue with this requirement had I not painted all of main steels in bitumous blackjack when they arrived on site on the recommendation of the fabricator and the SE. It is not practical or even possible to undo this at this point given that the goal post is now either fully or partially embedded in the walls. I was planning to pink board over this but am not sure whether I have a serious issue to contend with now. I've had BC control out 3 times since the steels went in and other than glancing at them to see that they were there there was no comment. 

 

Would appreciate any advice on what if anything I need to do.

 

Thanks, Paul

[Nickfromwales]

Hi.

 

If this is a standard domestic residence, you only have to apply intumescent paint if the steel is visible at the point of completion. 
 

If it’s behind (regular) plasterboard and skim it’s already got the requisite 30 mins FR, so no probs; unless your BCO says different?

 

A lot do, so I suggest you challenge and then they’ll back down, as long as the steels boxed in/is set into the fabric of the build. 

[Conor]

Where are the steels? If they've been waterproofed, then they are either embedded in masonry or on the outer leaf. In that case you wouldn't need to fire proof them. It would only be exposed steels within the building, that you wouldn't have painted.

 

Pink boarding is completely acceptable, if the steels are fully covered by them. 

 

You won't be able to paint intumescent paint over the steels you've already painted with bituminous paint.

Edited 14 hours ago by Conor

[Nickfromwales]

21 minutes ago, Conor said:

Pink boarding is completely acceptable, if the steels are fully covered by them. 

Doesn’t need to be FR PB unless it’s not being skimmed. Regular (white) PB + skim gives 30 mins FR. If FR PB isn’t getting skimmed then you need 2 layers, joints staggered, gaps/joints filled with intumescent caulk. 

 

BCO’s ask for this all the time until I push back. A lot just say what they’d ‘like to see’ vs actually state the regs.

 

Only time this all shifts is when it’s more than a 2 storey building. 

[paro]

Thanks everyone for your responses. Of all the things I am trying to figure out at the moment this was not on this list and had me worried last night as retro fixing it seemed next to impossible. 

 

Thinking about it I do have a 90mm SHS corner post where the glass doors intersect along with steels above to hold the wall up. These are galvanised. The post will be wrapped with aerogel but hadn't really got a plan for the top steel. I've no issue priming/painting this though as it doesn't have the blackjack all over it.

[Nickfromwales]

Just now, paro said:

Thanks everyone for your responses. Of all the things I am trying to figure out at the moment this was not on this list and had me worried last night as retro fixing it seemed next to impossible. 

 

Thinking about it I do have a 90mm SHS corner post where the glass doors intersect along with steels above to hold the wall up. These are galvanised. The post will be wrapped with aerogel but hadn't really got a plan for the top steel. I've no issue priming/painting this though as it doesn't have the blackjack all over it.

Is the steel exposed to the room? Or will you stick PB to it so you can paint cosmetically?

[paro]

Internally PB. Externally it will be exposed and likely clad with some kind of alu trim. 

[Nickfromwales]

If PB and skim, you only need to deal with it (internally) for FR, unless otherwise specified by the BCO. You need to get some clarification here tbh.

 

If they’re happy with the rest of it painted (external element) then happy days. 

If you need a structure to affix the alu cladding to, then another option would be 9 or 12mm cement board which would negate the paint (you’d have to check with BCO but they should be happy with that), as long as joints are sealed with FR mastic 

[saveasteading]

It's fair enough for the  building inspector to want a formal proposal. Your drawing shows intumescent paint, which you can't use, so your designer or another competent person needs to confirm it is now to be pb, including the spec and thickness.

Some bco's will be sufficiently trained in the fire reg's to be allowed to advise*,  so it's worth just talking to them first.

 

*their insurers will be very wary of fire risk and responsibility.

[paro]

Thanks. I've got a call with the BCO tomorrow so hopefully get a steer in the right direction.

 

I did contact a company that sells the paint but it turns out this is way more of a thing than I had appreciated. I need to complete a form detailing all the specs for the steels to come back with a recommendation. It sounds like this is something I'll need get someone in for as a lot of boxes seem to be needed to be ticked. I was a bit miffed at the suggestion that the expensive extra coating of zinc galvanising might need to be stripped off. 

 

Having said all this. The only reason the shelf is exposed is because I wanted to house the glass doors in the cavity for aesthetics, maybe I just go with sitting them in the outer leaf.