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DIY: Exposing a Steel Beam & Fire Protection

how to fireproof a steel beam with paint

Steel beams - you either love them or hate them. Their purpose has absolutely nothing to do with being an interior statement, but to safely support the building that sits on top of it. However with industrial interiors becoming a growing trend, there's nothing that quite punches a statement of industrialism more than an exposed steel beam. But keeping a steel beam as a feature to a room isn't quite as simple as it sounds. Nope, there's building regulations to adhere to and safety aspects to consider first.

Current building regulations (October 2016) state that steel beams must be protected against fire. Whilst steel obviously isn't going to set alight and burn to the ground - it can get very very very hot and bend or warp under extreme heat. If this steel is holding your house up - well, it wont be holding it up for much longer if this were to happen. For this reason, steel beams are covered in either two layers of plasterboard of one single layer or fire-rated plasterboard. Both of these give fire protection to a steel beam for so many minutes (usually 90!).

You can't simply keep a steel beam exposed as there's no protection for it against fire - which would firstly invalidate your home insurance as it doesn't adhere to current building regs. But even worse, it could cause considerable side effects if a fire were to ever break out. Therefore to expose a steel beam, it must still be fire protected in some way.

exposing a steel beam

If you've been following our kitchen renovations, you'll know we had a pretty chunky steel beam installed when we knocked through the kitchen and dining room. We were keen (or I should say, Grant was keen!) to keep this exposed. After all, it's not every day you get the opportunity to show off an industrial sized steel beam within your home! I have to be honest though - it wasn't the look I was really going for when I had first envisioned this room, but the idea grew on me over time and I decided to give it go. If I absolutely hate it - well, I can always cover it up right?

So I did heaps on research on this topic and thought I'd share how to expose a steel beam properly and safely if this is something you're considering too. So here's a quick snap of our steel beam - it's a UC twin steel which means there's two of them bolted together either side.

steel beam in kitchen renovation

Intumescent Paint

How does one fire proof a steel beam without plasterboard? The answer is intumescent paint! It's a paint that basically swells up during excessive heat and protects whatever's underneath. There are a few companies out there who will paint and protect a steel beam for you, but the cost of that I'm sure is far more than I was ever willing to spend. For DIYers, there are a few companies that sell intumescent paint, but it's still by no means a cheap product to buy. Particularly compared to fitting a piece of fire-rated plasterboard which would have been less than £10!

The paint we're using is by a brand called Zero Flame which we purchased from Rawlins Paints.

intumescent paint for steel

How Much Paint Do you Need to Use?

This depends on the brand of paint, the total amount of surface area you're painting, the type of steel beam, how many sides will be exposed and how many minutes of fire protection you need. Yes, it sounds so very complex and I'm not going to lie - figuring this part out wasn't exactly the easiest. There's a very simple chart on the back of the tin that translates this much simpler and easier, but it still wasn't very fool-proof in my opinion. If you're unsure, please ask your local building control.

So in our case, we're exposing 3 sides, it's a horizontal beam and has surface area of 2.2m squared. According to the chart we needed to buy a tub of 2.5l and use just over 2/3 of the tub. Yep, it's really that non-exact in calculations.

how to use intumescent paint

How to Apply?

The paint I'm using claimed to be suitable for brush application, roller application or spray application. I thought using a brush would be the easiest with the inner corners on each side, going around the bolts and with it generally being a bit of a tight space. It turned out however, that using a brush was a big mistake.

This paint is SO ridiculously thick it's unreal. I found it pretty much impossible to spread out and don't even get me started on the brush strokes that were horrendously visible. It was a very difficult paint to work with and every time I went back over a section of paint to add more paint next to it (like you would, when you're painting), it almost blistered and left a bumpy surface. I was really struggling! My first impressions weren't great and I had some serious buyers regret. It was a bit of a learning curve to say the least.

blistering intumescent paint

So I then opted for a small sized sponge roller, which applied the paint sooooo much better. After two layers of bad application, I had to add a few several layers to mask the brush strokes, but the texture and finishing surface was infinitely better. If you've ever seen painted steel before (often found in warehouses), it always looks coated - and I now know why. This paint is like tar!

So, a quick few tips for application:
  • Make sure to keep stirring the paint - One of the reasons my brush application went horribly wrong was because the paint kept thickening in the tub. One good stir is not enough to keep it at a workable thickness, you have to remember to keep stirring it every now and then.
  • Use a roller, not a brush - Using a roller really helped to deal with the whole brush stroke problem. I was able to apply the paint much thinner and quicker with a roller. You will need more coats, but it's definitely worth it! I actually used a sponge type roller which I think helped loads!
  • Don't be tempted to add another coat too soon - This paint blisters like crazy with a paint brush, even if you add more paint just 2 seconds later. Be sure to let the paint dry thoroughly between coats or you'll end up with bumps all over the place.
  • Use more paint than you think you need - So we needed to use 2/3 of the tub, which quite frankly was just an awkward measurement. You definitely don't want to use less paint than required, so to be on the safe side I highly recommend using a bit more paint than you think you need.
  • Sand/Scrape off any imperfections between coats - If you do have any blistering or lumps and bumps, you can sand or scrape these off between coats. It's not really a sand-able paint, but if you work at it, you can reduce any imperfections this way if things don't go quite to plan.

If I were to expose a steel beam again, I think I would try another brand called 'bro-steel' by Bollom which claims to be "ultra-thin". After discovering just HOW thick this paint really is, this certainly sounds like a winner to me.

painted steel
intumescent paint on steel beam
white painted steel beam
how to make a feature of a steel beam

Can You Add Colour?

The intumescent paint I'm using (and almost all the other brands I came across) claim you MUST use their brand finishing coat to add colour and cannot use regular paint over the top. How true this actually is, I'm not so sure. The finishing paint I'm using by by zero flame has absolutely no fireproofing properties, so it really doesn't add any other layer of protection, which is why I question this.

Non-the-less, we do need this steel beam to be signed off by building control and I certainly didn't want to take any chances, so we did opt for their CRAZY overpriced finishing paint. Seriously - the cost for this was more than the damn intumescent paint!! This paint is really just like any other regular eggshell - it's much more thin and watery, can definitely be applied with a brush, leaves no paint stokes and only needed a couple of coats to ensure a good spread of colour.

Considering a little goes a long way, I WISH they had sold a much smaller tin. A 2.5L tub for this size steel is absolutely crazy and I virtually have the entire tin left. We've gone for a colour called 'copper brown' which funnily enough, is pretty much almost the same colour as the steel beam was originally. There's plenty of colours to choose from, but sadly no testers so it was a bit of a risk anyway. To be honest, if I change my mind on the colour - I will probably just use a regular eggshell paint over the top. It's the bottom layer that does the protecting and I can't really see how a finishing coat could really affect that. Don't take my word for that though! And do let me know if you know any reasons otherwise why this might be a bad idea!?

painting a steel beam
fireproofing a steel beam with paint
colouring a steel beam
exposed steel beam

steel beam feature in kitchen
diy painting a RSJ steel

How to get Certification and Sign off?

Now that your steel beam is fully fire-protected, you can finally apply for a sign off. The paint I've used comes with an application to acquire a certificate from the paint company. You simply fill in details such as surface area, type of beam, date of application and sign a pledge agreement to state that the paint was applied to the proper specifications. You then send this off (with a fee of £6 - bit cheeky considering the already extortionate cost of paint!) along with the receipt for the paint and receive a certificate in the post which you can give to building control who will then be able to fully sign off the steel beam. It's as simple as that - although I'm still yet to receive my certificate on account of only recently having sent it off. Whoops! Hopefully, it will be as simple as that though.

certificate for painted steel beam

So that's everything! Here's a few shots of the finished steel beam in all its painted glory! We do actually intend on putting some bolt caps over the nuts and bolts for a more sleek finish. I'm pretty pleased with it otherwise - I just hope it doesn't look too out of place when we get to having a finished kitchen.... It's not exactly industrial themed, so hopefully the two different styles we're now going for will gel together okay. (eep!)

RSJ painted beam
exposing an RSJ with paint
steel beam feature in kitchen
painted steel beams

What do you think? Yay or Nay? Should I have picked a more daring colour? And would you expose a steel beam in your home?

(rounded to the nearest pound)

New Tools Purchased:
Brushes £4
Roller and Tray £2

Materials Used:
Intumescent Paint £52
Finishing Eggshell £60

Total: £119


  1. I think this looks great! May I ask roughly how much it was to knock wall down and put beams in? Only just found your blog and have already been browsing through a few posts (love your DIY fire pit!). We are just about to complete (all fingers crossed!) as first time buyers of a 1930's semi. Hopefully we'll be in early in the new year. Scanning all diy/interior/renovation blogs I can find at the moment for inspiration for our new home. Will definitely pop back :)

  2. Oh never mind my question re. cost, got to your post about knocking the wall down eventually :)

  3. This was so helpful thank you so much for posting really appreciate all your photos and details :)

  4. Hi, I'm just about to do exactly the same to our steel beam, I just wondered if you knew how long you fire proofed your beam for? So did you coat it for 30 mins of protection or 60 mins? I cant seem to find an answer on what building regs require. Looks great though! This makes me feel a lot more positive about my job!

    1. Hey! We went for 60 minutes of protection, which is the same level of protection as the pink fire-rated plasterboard. You could always email your local building control though if you're unsure - I sent no end of questions and they were really helpful!

  5. This looks great and kudos to you for taking the effort to do this...Its these little things that add to the overall look.

    Personally I would have liked to have seen a dark grey (powder coated style), but its your kitchen....Thanks I have found this really useful....I am told I have 12 beams may pay someone to do it


  6. We love the result! It's a great idea to celebrate and expose construction parts which used to be covered.

  7. This comment has been removed by the author.

  8. Really a wonderful article! i like it very much.

  9. Looks good. About to do this ourselves. Think we will have 3 big steels all joining each other, so a lot of work to do & quite costly. But I think it's worth it, as it's so much more unique than as plazterboard box. Do you know if it's definitely ok to only paint the exposed sides?

  10. Hello,

    stumbled in your blog when finalising the purchase of the intumescent paint for our steel and gathering tips and tricks on how to actually paint it, seeing that indeed it is a very thick paint!
    I just REALLY wanted to comment on the idea of covering the intumescent paint with "normal" metal eggshell.
    I had exactly your same concerns and I challenged two guys of two different companies about it; seemingly, indeed it is the bottom layer that does the job of protecting, but the colour layer is specially chemically formulated not to hinder the charring and swelling properties of the base layer.
    Whether that is true or not, I cannot say, but personally I don't like to play with fire (pun!).
    The whole thing is a bit ridiculous though, as you cannot hope that an unknowingly someone moving in into a house which has an already exposed RSJ does not decide to paint over it with normal metal eggshell; I for starter did not know anything about intumescent paints up until a couple months ago!

  11. just wanted to say thanks for writing this article up, even my builder had no clue you could have building regs compliance with an exposed beam.

    I would strongly advise the use of a primer, pre-application.

  12. We have just had exposed beams put in and are midway through our build. Our beams came pre treated and have a nice finish so will hopefully be easy to paint afterwards. Worth looking into, our builder got them very easily

  13. thanks for the tips and information..i really appreciate it.. Website

  14. Excellent info.Thank you so much. Got my paint coming next week and I'm wondering, when you used the roller, did you empty the intumescent paint into a tray first or dip the roller into the paint pot?

  15. Hello,
    Thanks for your post.
    Did you end up receiving the certificate of conformity? I'm interested in doing something similar in my kitchen.

  16. Thank you for posting and allowing us to learn more idea!

  17. This is so useful, thank you! Can I ask how you finished the area above the beam and below the ceiling? Did you use plasterboard to cover the bricks?


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