Marylebone Square: Case Study Transcript

We started the Marylebone Square project in November 2020 with the enabling works, which involved installing king posts, followed by piling. This led nicely into the temporary propping scheme we’re doing here with Kier, Morrisroe, and Conquip.

This is a very complex project — one of our biggest at the moment. It’s a three-level basement.

The first level of props goes in from capping beam level, about a metre and a half below street level. The next level is around six metres down at B1 level, and the third level is in the south section of the site, approximately another five metres below that.

Due to the high loading on the east side, we had to employ a double stack waling beam. Additionally, shear keys were welded because some props were working in a raking fashion. That was one of the additional design challenges Conquip had to develop.

We had bespoke propping in front of a transfer beam because we did a top-down construction of the temporary substation. We had to work underneath the permanent structure to install it, which required slight tweaks to the design. Working with Conquip and Morrisroe, we managed to overcome this issue.

We realised that the tower cranes needed to be erected as early as possible to facilitate prop installation. Initially, crawler cranes were planned, but because the dig was progressing so quickly, tower cranes had to go in early. Conquip helped with the design of the grillages and the top-down scheme for the tower cranes, providing a very quick turnaround. When changes occurred, they updated the design promptly.

This is the second project I’ve worked on with Conquip. Their engineers were on site the first day, not afraid to get their hands dirty. They set everything up and explained the drawings, showing how everything went together. Sections and props were numbered, and they stayed patient with us all day until it was handed over to Kier — everyone was happy.

We’re adjacent to a national school on a one-way street, with embargoed times where gates must be closed and no deliveries or large vehicles are allowed. Conquip has been very helpful with transport, adjusting schedules to suit site requirements.

One advantage of using Conquip is that we purchased props for a previous project, Madison, which they were able to value-engineer and incorporate into the main propping scheme here. Everything was delivered on time and worked very well on site. I highly recommend them.

Conquip brings design expertise and offers a variety of products and services — a true one-stop shop. They’ve been helpful and friendly throughout the project, responding immediately to any issues. It’s been a pleasure working with them.