Two quotations for what looks like the same sliding door can differ by a large margin, and the reason is usually that they include different things. A 'sliding door' is not a single product; it is a package of glass, frame, track, drainage, installation and — sometimes — motorisation, and each of those can be in or out of the price. Understanding what a quotation includes is the only way to compare two of them.
Supply only versus supply and install
The biggest single difference is whether the price includes installation. A supply-only quotation is the door delivered to site; the builder installs it. A supply-and-install quotation is the door fitted by the supplier's team. The two are not directly comparable, because the installation of a minimal-frame door — setting the track flush, draining it, concealing the perimeter, commissioning the hardware — is a significant part of the work and a significant part of the cost.
We supply and install with our own teams, including Swiss-trained installers for the Vitrocsa systems, because the installation is where a minimal-frame door is made to work or not. A supply-only door installed by a team that has not been trained on the system is a common source of the problems people blame on the door.
What is in the glass
The glazing unit itself can vary: double or triple, the thickness, the low-e coating, the warm-edge spacer, the tint or solar control. Two doors with the same sightline can have different glazing, and the glazing is a large part of the cost. A quotation should state the glazing thickness, the build (double or triple) and the Ug; if it does not, the comparison is not like-for-like.
Acoustic and security glazing add more. Laminated acoustic glass, or security glass tested to RC2 or RC3, is a different unit from standard double glazing, and the price reflects it. If a quotation does not state the glass type, ask.
Threshold, drainage and perimeter
A flush threshold with integrated drainage, a perimeter frame concealed into the wall, and an ACO drainage cover are all items that can be in or out of a quotation. They are building work as much as door work, and a quotation that does not include them is not the same price as one that does, even for the same door. This is where most of the 'it was cheaper until we started' surprises come from.
Motorisation, if specified, is another item that can be quoted separately. The larger panels — over 500 kg — are usually motorised, and the motor, the controls and the commissioning are a line item. A quotation for a motorised door should state the motor, the control method and the commissioning.
How to compare two quotations
The only way to compare two sliding door quotations is line by line: the system, the panel count and size, the glazing build and thickness, the threshold and drainage detail, the perimeter concealment, the installation, and any motorisation. A quotation that lists these is one you can compare; one that gives a single number for 'the door' is one you cannot. Our quotations set out the package in full, because that is the only honest way to price a minimal-frame door.
- Supply only or supply and install.
- Glazing build, thickness and Ug.
- Threshold type, drainage and perimeter concealment.
- Motorisation, controls and commissioning, if specified.
- Installation by a team trained on the system.
