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Citi Homes Windows

What to expect from a window and door site survey? And why it matters before you buy?

It is usually the site survey that is carried out as part of a glazing installation that is more likely to be purely procedural than substantive. The supplier comes to take measurements, the order is placed, and the installation is completed a few weeks later. In those instances where the process is successful, it is usually the case that the site survey has been comprehensive and any difficulties that might have created problems have been solved prior to the commencement of production. If, however, the process is unsuccessful, with problems like ill-fitting frames, structural complications during installation, or planning requirements coming to light post-order, then invariably it will be a consequence of inadequate surveying.

Why measurement of sites in London can be difficult?

A high proportion of glazing jobs come from Victorian and Edwardian terraced housing in London, and this type of property has one common factor which makes it important to measure accurately: it is rarely built square and level. Arches of brickwork sag unevenly, building foundations settle slightly over a hundred years, any changes made previously will create different levels and lines, and there are great variations in building standards even within the same street. A drawing showing an opening width of 900mm could be 910mm high and 893mm low, all without there being any mistake.

The frame made according to the dimensions shown in the drawing instead of the true dimensions of the aperture itself will not fit. The result is that the frame either won’t fit because it is larger and needs to be packed, or it is too small. In both cases, the work won’t be finished properly on the day. This creates unnecessary delays, added expense, and possibly even the need for the frame to be remade. All reliable window makers insist on the measurements being taken and verified on-site by the installer before manufacture for this very reason. Where a supplier insists on offering a fixed price based on a drawing or photograph alone, then that company must be assuming something.

What a glazing survey entails?

A correct glazing survey measures the width three times, at the top, middle, and bottom, as well as three times for height, at the left, right, and centre of the opening. The tolerance during manufacture is taken using the smallest measurement so that the glazing can fit without force. If there is any difference between the two diagonal measurements, then the opening is clearly out of square, and the frame must be manufactured according to its true size, which may not be a rectangular shape. While this is not uncommon in London buildings, it is easily solved when known during the glazing survey but quite difficult if found upon installation.

The survey also includes reveal depths – the depth between the outer face of the wall and the inner face – which indicate the type of fixing detail required and if the reveal depth allows for the profile depth of the frame being used. Shallow reveals are typical with Victorian brickwork and may restrict the selection of frame profiles. The sill condition is routinely considered: If the sill is deteriorated, cracked, or poorly sloped, it is vulnerable to water infiltration at the interface with the new frame, no matter how expertly installed the frame is. Finding the sill problem during the surveying process enables it to be included in the project scope and resolved as part of the process.

Lintels and wider openings – structural checks

A lintel is a structure placed above the opening that supports the weight of the wall above. It is normally made of a brick arch, stone flat arch, or steel flat bar, based on the original dimensions in Victorian or Edwardian building construction. The issue of checking the integrity of the lintel becomes simple when no widening of the opening is planned. Checking of brickwork cracks above the opening, curvature of the head frame, as well as any evidence of rust staining would be sufficient.

In cases where the opening is being expanded, to accommodate a wider bifold or sliding door, there is no doubt that replacement or reinforcement of the current lintel will be necessary. It is always important to have a structural engineer check the condition of the lintel before work begins; this is always done for such a project and needs to be considered in the planning phase. The surveyor who points out the structural integrity of the lintel during the surveying process is doing his/her job right; one who ignores this matter entirely is neglecting the obvious.

Planning issues: determined during the survey, not identified later

The London surveyor must determine, as part of the survey process, what the planning position is for the premises to be surveyed. This means finding out whether the property in question is in a conservation area, whether it is listed, and if the work proposed is within permitted development or will require planning permission. This is even more important in London than elsewhere in England since there are around 1,000 conservation areas across the 33 London boroughs and some of the boroughs have Article 4 Directions that take away permitted development for the replacement of windows and doors. Installation of windows without the required permission is a planning offence for which the property owner, not the builder, is responsible.

Proof of compliance with Building Regulations must be obtained as part of the normal surveying process. The specification must comply with the current minimum whole-window U-value of 1.4 W/m²K for replacement windows in occupied dwellings under Part L of the Building Regulations in England. New buildings, along with certain change-of-use conversions, will have to satisfy Part Q requirements that any easily accessible windows and doors comply with PAS 24, which is the British Standard on enhanced security performance.

What the survey process should deliver?

By the end of a properly conducted survey, the client should have confirmed the size of their openings, the manufacturing tolerances stated; the specification of the product to be installed together with the justification of why the particular recommendation has been made; an understanding of the stage the project is at regarding planning approvals needed before placing an order; and a firm fixed price quote based on measured dimensions. This is when lead time needs to be considered – top quality aluminium window and door systems take six to twelve weeks from placing the order to installation.

An estimate that provides only a verbal estimate and a rough idea of price to be verified later is no estimate at all. All the hard work and all the risk are postponed until after the customer is left in the position where they have even less control over cost and requirements than they did before they asked for the estimate. The reason for the estimate is to clarify everything well ahead of time, so the installation will go smoothly and there are no unpleasant surprises.

Our approach to conducting surveys at Citi Homes Windows

At Citi Homes Windows, all of our projects start with an on-site survey before any specifications or orders are made. This involves measuring the dimensions of every opening, evaluating structure and sill conditions, reviewing the details of the lintel, confirming planning permission, and specifying the appropriate window for the opening and building. The survey is a component of our procedure, and it is provided free of charge and without any obligation to move forward. Where something comes up in the survey that impacts the project cost or scope, it will be discussed and agreed upon prior to the production of a quotation.

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