DIY: Exposing a Steel Beam & Fire Protection - Kezzabeth | DIY & Renovation Blog (2024)

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.

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.

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.

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.

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!?

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.

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!)