The steel erectors have arrived on site and already the building is taking shape. Working initially along the Greyfriars Road, the building will rapidly emerge in phases over the coming fortnight.
Qualified steel erectors work in tandem with the foreman and crane driver to hoist each piece of steel into place before bolting the parts of the frame together.
As the building takes shape, scaffolders will return to bind the scaffolding to the frame to provide a safe working environment for the trades that follow-on.
George & Patrick.
The Erectors with Crane Driver
We express our thanks to Steel Fabricators Newnham Structures newnhamandabel.co.uk and their erectors AJF Site Services www.ajf-fabrications.co.uk
The first three loads of steel for the steel framed building have arrived and are being offloaded by crane. Each piece has been fabricated to fit precisely in its place and offloaded in the order it will be used by the steel erectors.
The erection process is split into eight phases that we expect to continue for the rest of April. But the building will take shape well before then. In the next few days phase one will be complete along Greyfriars Road with temporary bracing installed to provide structural rigidity until the concrete floors are poured.
The mobile crane with jib extension.
The steel showing the erection phases.
Just 20 of the total of 170 tonnes of steel that will eventually form the entire steel frame.
We have now securely grouted about 250 bolts into precisely positioned holes in the ground beam with special resin in advance of the delivery of the steel frame next week. It is said that the special resin is stronger than the steel bolts or the concrete.
The bolts will anchor the frame in place. Later, concrete floors within the frame will be laid to give more structural rigidity. As more floors are erected, scaffolding and fall-arrest features will be installed to ensure the safety of the specialist steelworkers.
An initial delivery of three trailers loads of pre-manufactured steel beams will start next Wednesday with erection of the entire 170 tonne steel frame by crane taking about three weeks with an estimated completion by the end of April.
We are now preparing for the arrival of the steel frame, which is currently being manufactured elsewhere in Norfolk. An integral part of this is the erection of the first stage of the scaffolding.
As the scaffolding will be covering the pavements on Rose Lane, a condition of the scaffolding licence and design is that crash decks to protect pedestrians as they walk underneath is incorporated.
This first phase of scaffolding will be just one flight high. As the steel frame is erected, additional flights will be added and tied-in to the frame.
The next step will be to properly hoard the site for safety and security during the above ground construction phase.
partially completed scaffolding being erected
After a month on-order, we have finally taken delivery of the all-important HydroBrake, which works to prevent surges of rainwater overwhelming the wider City drainage network after heavy rainfall.
It works with the subterranean lagoon crates to hold-back rainwater and is the last thing that needs to go in the ground. When connected to the other pipework in the next few days, it will enable us to do final levelling of the site and to apply a rough tarmac surfacing that will provide a good safe operational base and prevent mud and dirt from being carried onto the road network during the above ground construction phase.
And that means that we can finally get the scaffolding erected next week in advance of the arrival of the steel frame in three weeks time. We are on schedule.
Lowering the hydrobrake in place and orientating to pick up the pre-prepared drainage pipes.
The stainless valve which regulates water flow.
We have been securing loose equipment and strengthening the perimeter fencing and removing the hoarding covers in preparation for Storm Doris this morning.
Our focus this week has been on preparing the car-park tarmac sub-base. This has meant levelling the site to the precise levels determined by the architect and civil engineer, informed by the precise togographical survey.
All this detail is important so that surface rainfall will move in the right direction towards the drains when the development is complete.
Our approach is to put down a rough tarmac surface for the construction period. It will ensure that the site remains clean and can be correctly managed during building and also means that mud will not be carried onto the road.
So we’re now laying down a thick layer of crushed granite, which will be mechanically rolled and compacted. A rough tarmac surface will laid on top of this shortly.
When the development is finally complete we will then put a second additional layer of higher quality tarmac down on top of the rough layer, which will be white lined and correctly dressed around the drainage ironworks and manhole covers.
We are still awaiting delivery of the hydrobrake valve which will be installed in the excavated hole and connected to the drains and public sewer.
After nearly three months ‘in the ground’ we are getting to the point where the piled reinforced ring-beam is complete and the surface and foul water drainage infrastructure is substantially installed above and below ground – albeit not connected to the public sewers yet. Only the hydrobrake valves now need to be installed.
Our next steps are to fine-tune the floor levels in the car park so that the manhole covers finish at ground-level. For this we will use the laser leveller. Next we will rough-tarmac the surface to provide a strong and clean base that does not bring mud onto the road during the above-ground construction process.
We are also planning for the erection of a substantial scaffold and pedestrian protection scheme on the pavement, for whcih a licence is required. This work will take place in the next few weeks.
The steel frame will be installed in early March on the ringbeam and a near-one metre void will give access underneath the finished floor level – useful for maintaining ongoing access to drainage pipes once the construction is complete. The ground floor of the building will eventually be level with Rose Lane pavement level once the floor beams, insulation and floor-coverings are added.
You can see the temporary brown drainage pipes projecting from the soil marking where the underground drains have already been laid.
The void is awaiting filling with the hydrobrake valve that holds back rainwater after a heavy deluge to prevent surface flooding.
We’ve been spending the last week in wet conditions connecting the surface water drainage infrastructure to the hydrobrake system. The drainage pipes sit on top of the foundation ring-beam and will remain in the void between the foundation and finished floor level when the steel frame is erected.
The process of filling the rainwater attenuation system with the special crates has progressed rapidly. An impermiable membrane is laid on a sand base, which prevent sharp stones from damaging the membrane.
The interlocking crates are stacked on top in multiple layers, each drawing structural strength from each other. The membrane is extended up the sides as the crates are layered to form a tank that will retain rainwater surges.
Finally the crates are entombed in an impermiable cover, which in turn is encased in a further sand layer before the being covered. The result is a hollow tank that is structurally strong enough to be driven over.
The next step will be to connect the closed box to internal drainage runs and the public surface water drainage system via a ‘hydrobrake’ valve.
One of the key conditions of our planning permission is to construct an underground holding tank for rainwater that would release into the sewer at a controlled rate after heavy rainfall as part of a stormwater management system. This ‘hydrobrake’ system prevents flooding to surrounding areas during and immediately after heavy downpour conditions.
Today we have been excavating the massive holding tank, which will eventually be filled with special crates that will retain water for a short time following heavy rainfall.
Following installation of the crates and connection to drains it will be covered over and will be located under the car park.
More concrete is being poured into the prepared reinforced cages this morning, which includes the complex area around the lift shaft The ring beam is now substantially complete with only a small portion to be completed near the temporary site entrance, which will be moved so we can excavate this part of the site.
The complex foundation work around the lift shaft is now complete and final preparations are being made for the final concrete pour of the ring-beam.
Work continues on exposing the piles for the rest of the foundation ring beam under the supervision of the archaeologist.
Exposing the four piles for the central lift shaft and dry risers
Over 36m3 of concrete has been poured this morning into the reinforced steel foundation by formworkers with the help of a 36m-reach concrete pump that is capable of reaching the far corners of the site.
Concrete being delivered.
The massive 36m concrete pump from Eastern Concrete able to reach into every corner of the site.
Concrete being poured into the pre-prepared trenches.
The finished product – filled to the precise height determined by the laser leveller.
Work continues on the six week ground-beam construction process, which is now over half-complete.
Formworkers place the steel reinforcing cages, which have been assembled on site over the exposed and tested pile caps, before the two will be stitched together.
This section is ready to be concreted later this week.
Following testing of the piles, final GPS Surveying and inspection by the Building Control inspectors, we have commenced pouring of the reinforced concrete ring beam in ideal weather conditions.
Pile caps have been protected and will later be drilled and grouted with bolts, which will eventually mate with the steel building frame.
With the dry and frosty weather in recent days we have been able to make excellent progress in good conditions with preparing the reinforced steel for the ring beam, ensuring that it is tied-into the steel piles.
Shuttering will securely retain the concrete within the ringbeam when it is poured.
The concerete pile-caps have been exposed and cut to the exact depth revealing the steel reinforcing. Temporary wooden shuttering is used at this stage.
A single pile that will support the undercroft parking.
Specialist formworkers prepare the steel reinforcing cages, which will be tied into the exposed concrete pile caps.
Our specialist form workers have been working hard to excavate the ground for the foundation ring beam. Overseen by a qualified archaeologist, they have been digging out the foundation and exposing the steel in the concrete pile caps, which will later be tied to steel reinforcing cages being constructed onsite. These will later form part of a strong reinforced concrete foundation for the steel building frame.
Exposing the steel in the concrete pile caps. The precise depth is determined by laser measures.
Steel reinforcing cages being constructed onsite for the reinforced concrete foundation
Now the concrete piles have set, we are carefully exposing the columns and digging the ring-beam foundation. The piles will be cut down and tested before exposing the reinforcing bars over the coming weeks. Formworkers will then link each pile to the reinforced ringbeam to produce a strong foundation for the building’s steel frame.