Supply-Only or Supply-and-Install: Which to Choose

Guide

Every metalwork package can be bought two ways: you take delivery and fit it yourself, or the fabricator measures, delivers and installs. The price difference is visible. The risk difference is not, and it is usually the larger number.

What each option actually covers

Supply-only means the fabricator makes to the dimensions you provide and delivers to site. Setting out, fixing, making good and any adjustment for site variance are yours. If a piece does not fit because a wall moved 20 mm from the drawing, that is a variation you pay for.

Supply-and-install means the fabricator surveys the site, works to their own measurements, fabricates, delivers and fixes. Because they set out from what is actually built rather than what was drawn, fit becomes their responsibility.

The measurement question decides most jobs

This is the crux. Metalwork is unforgiving — a balustrade or a door frame either fits the opening or it does not, and steel cannot be trimmed on site the way timber can.

Buildings are never exactly as drawn. Openings go out of square, floor levels vary, columns end up a few millimetres off grid. When the fabricator measures, they absorb that variance. When you supply dimensions, you own it.

So the honest test is: are you confident enough in your site dimensions to warrant them? If the structure is finished and you have surveyed it, supply-only is reasonable. If the building is still moving, it is a gamble.

When supply-only makes sense

• You have your own installation crew who fit metalwork routinely.
• The item is repetitive and modular, at standard sizes, with tolerance designed in.
• Site access is difficult or restricted in a way you already manage.
• The programme requires you to store components and fit them in your own sequence.
• The structure is complete and accurately surveyed.

When supply-and-install is the better buy

• Fit is critical and visible — frameless glass balustrades, entrance doors, curtain walling.
• The installation needs specific skills or tools: chemical anchors, structural glazing, site welding, alignment across long runs.
• You want one party responsible if something does not line up.
• A warranty on the installed result matters, not just on the goods.
• Site dimensions are not yet reliable.

What supply-only costs that is not in the price

The saving on the invoice is real, but the full cost includes your crew's time, lifting and handling equipment, fixings and consumables, storage and protection between delivery and fitting, and the rework when something needs adjusting. On a small job these are minor. On a large glass or facade package they routinely exceed the difference in quotation.

There is also a warranty gap worth understanding: on supply-only, a fabricator warrants the goods but not the installation. If a panel later works loose, the argument about whether it was made wrong or fitted wrong is one you have to win.

Splitting the package

Many projects do best on a mix. Buy the structural or hidden items supply-only, where tolerance is generous and your own team can fit them, and buy the visible, precision or safety-critical items installed. Railings on a straight run of external stair are very different from a frameless glass balustrade around a stairwell, even on the same job.

What to ask before deciding

• Who takes the site dimensions, and when?
• What happens if the opening differs from the drawing?
• What does the warranty cover in each case?
• Are fixings included, and are they suitable for the actual substrate?
• Who is responsible for protection until handover?

We work both ways across all five service lines. See railing supply and install, or tell us about the project on our contact page and we will say which we would recommend and why.