Installing the Steel Work
The custom steel work has been fabricated and delivered to site so the installation of the beams to support the second storey of the extension can start. The footprint of the second storey is smaller than the ground floor part of the extension so the steel work has been designed to accommodate this. A steel beam will be fitted at first floor level in the original back wall of the house. Another steel will be installed spanning between the two new flank walls of the extension. This will be set back from the back wall of the ground floor section. Another steel will then be fitted between the two to provide support for the side wall of the second storey which is also set back.
As you can see from the pictures, the steel work is delivered to site already primed and ready to be installed. You’ll also notice that many sections are pre drilled. The reason for this is that the two largest beams will be made up of two sections bolted together end to end. The steel work specified for this job is fairly heavy gauge and installing them as single pieces would have been near on impossible bearing in mind the access restrictions and how heavy a single beam of this gauge would have been.
The back wall of the house had precious little in terms of footings. Foundations had to be dug out and concrete poured to create a suitable base for the brick piers supporting the steel. A brick pier is left at one end of the original wall although the top needs to be made good with a few new bricks. At the other end where the old store room doorway used to be, a new one is built.
Holes the size of a single brick are cut out at regular intervals across the back wall at first floor height. Acro props are then set up with strongboys mounted on top. The plate of the strongboy is positioned in the holes and the props jacked up. The weight of the upstairs wall is now sitting on these supports. As one of the G L Smith and Sons team tells me, the brick work of the old wall is bedded with lime mortar so, unlike bricks bedded in sand and cement mortar, they can easily move. On the inside, another series of acro props is set up with a timber head plate spanning all of them. This will give additional support by taking the weight of the floor of the room above which, in due course, will be resting on the new steel.
With the wall now fully supported on the acros, work can start on cutting out the back wall and install the steel. As before, any bricks that can be reused are cleaned up and salvaged as they go along. It’s not long before the opening is completely cut out and you begin to realise what a good size the new room is going to be.
The steel to go in is made up of two sections. These were laid on blocks on the ground between the two sets of props so that they could be joined together. You wouldn’t want to make the mistake of joining the steels when they were the wrong side of the props - there are 36 heavy gauge bolts to do up ! The new steel is hoisted into position using a manual hoist – a bit like a hand operated fork lift.
It’s gradually manoeuvred into position so that it sits over the brick piers at either end. It’s then jacked up with acro props so that it is perfectly level and aligned. Slate packing pieces wedge the ends where they sit on the brick piers. Spaces above are packed with brick and slate so that the steel is taking the load. The brick work above is then made good .
The second steel to go in is a little less complicated but still made up of two sections and every bit as heavy. Recesses have been left in the flank walls with their base lined with a couple of courses of engineering bricks. The hoist is used to lift the steel up and sit one end in the recess. The other end is then packed up with a few blocks on the scaffold. The other section is lifted and positioned in the same way. The two sections are manually adjusted so that they line up perfectly with one another and are sitting on the engineering bricks at each end by the correct amount. The steel plates for joining them are fixed in place with no less than 36 heavy gauge stainless steel bolts !
As the brick recesses on each of the flank walls are absolutely level with one another and set at the exact height required for the steel, no slate packing is needed on this one. The last section of steel to go in is of slightly smaller dimensions making it a little easier to manoeuvre. This is hoisted up and sits perfectly at right angles spanning the previous main steels. Taking measurements from the drawing the steel is positioned as the base of the upstairs flank wall. The depth of the steel is less than the main ones so it is packed up with slate wedges until the upper surfaces are all level with one another. On each end of the steel are pre drilled flanges which will be used to bolt it to the main steels with yet more stainless steel bolts.
This has been quite a feat installing some surprisingly heavy gauge steels but the final result is pretty impressive. There’s no doubting that the steel work is up to the job !
If you live in the Hertfordshire area and are looking for a professional building contractor, you can get in touch with G L Smith and Sons via their website: http://www.glsmithandsons.co.uk/
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