Picture 4: It was well worth £100 to Homebase to protect this entrance.

Stainless steel is coming into its own in armoured joints.  Andrew MacKenzie of Permaban explores how new manufacturing methods and product design are making stainless steel an attractive option for arris and door threshold protection.

AlphaJoint was developed in the UK and introduced to the concrete flooring industry nearly ten years ago.  Steel armouring of arris edges for free contraction joints has become the normal approach in heavy-duty situations such as distribution centres.  However, there are also some clients who don’t have an unduly heavy duty requirement but do have a strong wish to avoid spalls and cracks in their concrete floors. 

In the food industry, for example, clients want to ensure their floors remain intact for hygiene reasons.  Retail warehouses want to maintain the appearance of their floors and grocery supermarket chains are starting to use directly in-situ finished concrete floors with coloured dry-shake.

Stainless steel top strips on armoured joints provide an ideal solution for these applications – and in the last year or two Permaban has noticed a steady increase in the number of enquiries for joints made with stainless steel. 

However, traditionally, stainless steel top strips supplied with the correct specification and tolerance were expensive, materials prices were not firm and availability not always prompt.  Thus a contractor might tender in good faith only to find issues of cost and availability perhaps a few weeks later.   

To overcome these problems Permaban has developed a “C” section stainless steel top strip for its AlphaJoint, with the patented Rigid Divider Plate stiffening.  By rolling this strip in a large quantity, and with the joint manufacturer acting as a stockholder, attractive fixed prices and shorter lead times are achieved.

Permanently preventing damage

While the main market sectors for these stainless steel joints are the food industry, groceries/supermarkets, the waste industry, DIY stores and other retail warehouses, there is another important application.  Every level-access goods door in the country would benefit enormously from being armoured at the threshold. 

The advantages and savings for the building occupiers are huge – less damage from incoming goods; less damage to products being dispatched; less forklift truck maintenance and bearing damage.  The appearance of the floor during the building’s use would be greatly increased – and at the end of the lease, costly concrete repairs to this area would be eliminated.

With such clear benefits, it’s easy to see that it will soon become totally normal to armour all these door thresholds with stainless steel.

Using Strip Joint Single, the ease of installation can be seen in the pictures 1 and 2. Any self-respecting builder would have the skills required and no special tools are needed.  There would clearly be a need for immediately available local stock to satisfy the smaller builders and, starting in Leeds, selected stockists are to maintain local supplies of Permaban’s stainless steel “C” section AlphaJoint, and receive informative material to advise and help.

Detailing

There will be occasions when a more complicated layout is required. Some clients require a 90 degree return on the joint at the doorways. In these cases the contractor can use a corner such as that illustrated in picture 3. These corners can also be used in modular fashion, using several of them to create 3-way and 4-way joint crossovers with timber formwork. Normal AlphaJoint can also be supplied with the stainless steel top sections and in many situations this would be a better option.

Applications

Homebase experienced ‘rust bloom’ after floors had been cleaned. Deeming this unacceptable, they now specify stainless steel AlphaJoint for free contraction joints and door thresholds.

Allied Bakeries have a high expectation of the appearance and performance of free contraction joints in their bakeries, and are specifying stainless steel AlphaJoint, with the top strips pre-spaced 2mm apart to assist in subsequent joint sealing mastic work. Two projects completed so far are their bakeries at West Bromwich and Glasgow.

An application for Aldi at a new store in Leicester used stainless steel AlphaJoint for a concrete slab.  This slab was diamond ground and polished to remove 2mm of the surface and expose the aggregate sections, mimicking terrazzo. The concrete was installed with 2mm self-adhesive protective strips laid on the stainless steel top strips to ensure the grinding was done on concrete and not on the steel – this would have damaged both the steel and the diamond grinding heads.

The floor for Morrisons new store in Newport, Monmouthshire, has recently been completed with mid grey coloured dry shake and stainless steel AlphaJoint. It was felt that stainless steel was the best choice, as frequent cleaning would promote rust blooming in mild steel finishes - not desirable in a food store.

More widespread

The use of stainless steel joint detailing has become more widespread, with clients selecting them for performance, hygiene and appearance.  This has become a greater consideration in supermarkets with the current trend towards directly finished in-situ concrete floors.

Level-access trafficked door thresholds should also be armoured as this gives huge benefits to the building occupier.  The work is straightforward and economical and Permaban envisage that in due course all such details will be armoured in this way.