Installing a RSJ

A RSJ is a rolled steel Joist, sometimes referred to a steel beam, steel girder or steel lintel. There are several types of these beam, the most common one is ‘I’ beam. A beam that is specified as UC 205 x 205 x 86 is a 205mm x 205mm beam that weighs 86Kg per metre. The length is usually stated in the calculations.

Installing a RSJ may seem like an impossible task for DIYers. My greatest fear was how will i support the house up and lift such heavy steels. I did ask myself many times, ‘shall i get someone in?’. Like always, in the end I decided to do it myself!

Building regulations require the beam to be sitting on a wall that will bear the load of any structure sitting on top of the beam. It has to be sitting on a ‘Padstone’ that is simply a very strong concrete block constructed to distribute the weight uniformly also allowing it to hold up the steel in case of an extreme fire. RSJ’s that are low load bearing can be placed onto a single skin of brick work with a pad stone with a minimum 100mm end bearing.  The brickwork below must have an adequate crushing strength to hold up the beam. In my extension, the loads are much greater therefore a new concrete foundation and brickwork had to be constructed from the ground to top.

I will keep this section simple and focus on one beam.
Looking at the calculations this pillar is smaller than the rest. 600mm x 600mm x 450mm deep. The brickwork specified on the drawings should be one brick wide by one brick deep. The pad stone specified is 225x225x150mm.

First to calculate the amount of concrete:

0.6m x 0.6m x 0.45m = 0.162 cubic metres. This I can mix myself as it will be less than a half of a ton of ballast.

I decided to go slightly wider and to make the brickwork bigger to 1 brick deep and 1.5 wide. This brickwork will not be keyed into the existing brickwork like before, this time it will be tied using 2 stainless-steel wall starters with extra bolts and brackets. Some more concrete:

0.8 x 0.6 x 0.45 = 0.21 cubic metres.

For this I will need 70Kg of cement, 396kg of ballast to produce a C20 mix. One ‘ton’ of ballast is really 850Kg. Half a jumbo bag and 3 bags of cement.
Cost of a Jumbo bag of Ballast is £30 and 3 bags of cement £12 approx. That leaves me half a Jumbo to use somewhere else.

Before I began I cracked off some plaster to expose the brickwork. What’s that wood beam???


I started by marking out the floor and then removing the floor tiles. The more rubble I removed the more came loose from the sides and fell in.

Then I cracked the concrete floor with a sledge-hammer and used the SDS drill breaker to break the concrete away.  The concrete was a very weak mix and the hardcore underneath was not compacted at all.


Thought I would check to the top. More wood beam?? It looks like an old door way.


At this moment I realised the poor workmanship of whoever layed the concrete floor.

I could have made this job a lot easier by removing a section of the wall however i did not want to expose the rest of the house to drafts as the weather was very cold at the moment.


On the other side of the wall is a timber suspended floor. I basically threw the spoil and bricks into the void to save me extra work completely removing them. It took a while to dig down enough for me to get into the hole and to dig underneath the wall in the middle.

I used one of the bricks that were sticking out as a guide for where the concrete may need to be filled up  to.


I then decided to go even lower and under-pin the existing wall at the same time so I went down just over a metre in the end. You can see I went 2 bricks lower than the existing wall.


I moved over half of the ballast jumbo bag inside ready for concrete mixing.


Mixing the concrete took half an hour on my own.


I tampered and levelled it using garden rake. I left the top rough so the mortar and bricks will key-in better. Notice the old clay pipe on the right. The concrete was filled way under this however it was left in to prevent the sides caving in.


This time I used imperial 73mm engineering bricks. These have a crushing strenght of over 50N/mm. The specification required was above 25n/mm for this pier.


For the entire pier I used a strong 1-4 mix.  I keyed in a couple of bricks into the existing wall below the dpc. Above the DPC I will be using heavy-duty wall starters.


Before starting the brickwork I did check the level of the existing wall to make sure it will construct vertically plumb by taking into account the wall starter thickness.


To make building this pier easier i fixed a piece of straight timber as a guide.

I learned by using dry bricks and keeping my gloves dry did not stain the bricks as much as before. I could have left this pier uncovered as a feature if I wanted to.

This timber lintel over the doorway was in the way of the bricks so needs to be removed before the last few courses of bricks can be completed. Before I done any thing else I need to mark exactly where the padstone will sit. I could only do this by exposing the other end and by making s direct line of sight for the laser.


After removing the plaster and exposing the old RSJ I was shocked to find out how the beams were sittings. The end bearing (over-hang) on the left hand side is so bad I had to quickly get a acro prop into place to support it up.


You can see the rsj above is resting on a brick. If this brick cracked the steel will fall. Work of a cowboy!


Back to the other side. This beam seems to go into the wall quite a bit. I acro proped one side to it could be removed without disturbing the wall above.


I simply drilled a hole to allow the recip blade to go into and cut it on both sides to get it out.


I marked the required height of the pad stone. This took a while to work out as the main beam is thicker than the one going into here by 10mm. Once it has been bolted the bottom will be therefore 10mm higher so this padstone needs to be 10mm higher to keep the beam level. This is important since when tightening the bolts the beam end plate will not go flush if the beam is not level.


I made an error and ordered the beam slightly longer. No problem just cut it using s grinder with a metal-cutting slittling disc. Before I cut it I had to calculate the angle the beam will have to swing into place. Basically to get the turn on a 3m beam you would have to cut the beam 10mm shorter.


The next step is to prepare the upstairs bedroom for the acro supports. I removed the skirting board to expose the bricks.


I noticed the brickwork had been recessed at this stage. That’s 2 courses of bricks that are hanging out by 30mm as a decorative feature of the house. I will to add a drawing later and explain what is required when packing the RSJ in.


At this stage I would have hired a Genie lift to lift the beam.  To save on the cost (approx £150 per day) and the hassle of clearing the floor for the lift and also considering that I would have to get the Genie lift all the way into here I decided to use the chain blocks. Also before I fit the acro props I need to get the beam into place above the old beam. Using the chains blocks I lifted the beam up and placed trestles under.  Then i built my scaffolding tower underneath.


It took a few hours on my own to get to this height. I used steel tubing to roll the beam on planks of wood to get it closer into place.


I could not get another level of my tower into place due to the low ceiling height. If found it very time-consuming balancing the beam onto blocks and using a trolley jack to lift the beam. I made sure at all times if the beam did fall it would not fall onto the scaffolding and not me.


I managed to get the new beam over the old beam after a good struggle. It can now easily be rolled into position.


I did calculate the length of the beam correctly to get the it to turn in. I measured from one end to the brick therefore the plaster was chipped away to allow the turn. I planned to remove all the old plaster in the kitchen anyway.

Now I would need to remove the temporary acros and reposition them on the otherside of the beam to support the timber floor joists above.

On the other side of the wall is the old external wall.


I placed another 3 acros to support the wall and floor on this side. I had to tension them very tight. So that’s 6 acros supporting the upper wall.


As i moved the RSJ into postition i made sure that none of the acros strongboys got disturbed. You can se that i will have 30-50mm space to fill in with concrete mix. I removed any debris so the RSJ would sit on the pad stone perfectly.

To join and secure the beams, i had to drill another 2 holes using a black smith drill bit. I used a standard cordless drill running at a very slow speed while applying a lot of pressure. If the swarf comes out in little bits try slowing down the drill. I also applied some WD40 to assit in the drilling.

The first hole took approx 5-6 minutes.

No signs of wear on the drill bit even though i did run it at high speed thinking it would drill faster. Slow and easy wins the race. The 2nd hole took half the time.

I made a couple of packers using 2 pieces of ply wood nailed together.

You can see the packer went in really tight. The bottom layer of sheet came away that ensured it was supporting the joist above