Frequently Asked Questions

Why use Test Valley Windows

Test Valley Windows is a local Company that has been established since 1995 that prides itself on customer service and quality. You can feel confident in this, as we were approached by Which? To become a Trusted Traders after our customers recommended us to them. Our attention to detail and constant drive to improve products, through many years experience, has enabled us to produce a product that will not only look good and perform to the highest standards, but it will also help keep your house secure. We have a no pressure sales policy and will guarantee that our advisers will never out stay your welcome but will offer good advice and help design our products to what you require. We will produce a detailed quotation, in writing, that will give you time to make an informed decision. Our honesty and desire to produce customer satisfaction is not just backed up by quotations from customers but is reinforced with names and photos, visit our page.

Below are a few of our frequently asked questions. When we quote, we like to carry out a site visit, so our professional advisers can produce a detailed quotation, to your requirements and one that will comply with regulations. We can undertake all planning and building regulation requirements, so you do not have to worry. It is, however, a sorry fact that a few Companies or proprietors may cut corners, so it is advantages that you are aware of what regulations and permissions that are required.

Do I require planning to replace windows and doors or to build an extension/conservatory?

If you do or do not require planning is dependant on many factors:

If the area you live in is a Conservation area, you may require planning for your extension.

You will require planning when there is an Article 4 Direction removing permitted development for all extensions. Also If there is an Article 4(2) Direction (generally City centres and places of historical interest) you may require planning to replace windows and doors to the front of your property or other alterations that alter the appearance to the outside of your property. An article 4(1) will extend the removal of some or all alterations to the whole outside of the property without planning permission.

If you live in a listed building, you will require listed building consent.

If you are a leaseholder, you may need to get permission from your landlord or management company.

Test Valley windows can undertake any planning requirements as part of your order.

Please view our Planning page for more detailed information.

Does my proposed conservatory require building regulations?

Normally a conservatory does not require Building Regulations if there is a thermal barrier between the conservatory and the house (an external grade thermal door for example).

What defines a Conservatory?

It should have:

At least 50% of external wall area formed from translucent materials (not including walls within 1 metre of boundary*).

75% or more of roof area formed from translucent materials.

Be at ground level.

Be effectively thermally separated from the main part of the dwelling.

Please note that certain regulations still apply to the construction of a conservatory. For further information please visit our planning page and view BEST PRACTICE NOTE ON THE APPLICATION OF BUILDING REGULATIONS.

What should I do if a shared sewer is running through my property in or around my proposed development?

The raising and sealing of a manhole cover inside a building will no longer be acceptable on a public sewer. On public sewers, the only option is to reposition the manhole cover outside the extension. This may not always be possible and will require a site visit from a surveyor or builder to carry out a survey. On private sewers (these are sewers that have no waste from other properties flowing through them) it will still be okay to raise and seal an inspection cover. For further information, please view information films at

If the diameter of the drain is over 225mm a build over agreement will not be permitted.

Under no circumstances can you build a mains water supply.

What are the implications of not having a Build Over Agreement when building over or within 3m of a main sewer drain?

Householders and developers planning to build close to or over a public sewer have to seek permission from the relevant sewerage company (some Building Regulation Authorities will undertake this as part of the Building Regulations if required). Building close to or over a public sewer without having obtained formal approval is illegal. It may also jeopardise the future sale of your property. If permission is not obtained the new extension may have to be demolished if the sewage drain is or becomes damaged, at the householder’s expense.

Do I require Building Regulations for replacement windows and external doors?

Building regulations are required when replacing your windows and doors (that have a glazing area of 50% or greater). This can be done through a FENSA registered Company like Test Valley Windows, for which we do not charge for this service when we carry out the supply and installation. Alternatively, your certification can be carried out through your local or independent Building Regulation Authority for which there will be an inspection charge.

I would like to change my conservatory roof to a solid roof, what is required?

When you replace a conservatory roof with a solid roof (not translucent material), then it is no longer a conservatory so it must comply with Building Regulations. To fail to do this may result in the structure being unsafe and compromise the future sale of your property. As conservatories do not require Building Regulations and are light weight structures, it is likely that other works will be required for it to comply (which may include the complete demolition and reconstruction). Please be aware of any Company that offers to change your translucent roof to a solid roof without Building Regulations approval.

What is FENSA?

FENSA (Fenestration Self-Assessment Scheme) has been set up by the Glass and Glazing Federation (GGF) in response to Building Regulation requirements for replacement windows and doors. Once your installation has been completed, by a FENSA registered installer, you will receive a FENSA certificate for the products installed (that require Building Regulation compliance).

Why would I require trickle ventilation?

It is important when installing windows and doors that condensation is taken into consideration. Condensation occurs when the moisture level builds up to saturation point and condensates, normally on the coldest spots. Warm air can also hold more moisture so when temperatures fluctuate, and a room becomes cooler condensation can form. This is normally on the glass of windows and doors, on reveals around windows, behind furniture and on thin walls and ceilings. There are some reasons for this moisture build up for example:

New boilers – Some older boilers and gas fires used to take air from inside the house and then exhaust the fumes and used air outside. This is not the safest way to design a boiler, or the most efficient, so modern boilers have a balanced flue which takes the air and disposes of the used air and fumes from the outside. This means that when this old type of boiler is modernised the new air circulation is reduced and can help to cause a higher moisture content in the air. This build up is caused by general living, for example, whilst sleeping a person can add around 1 litre of moisture into a room.

Insulation of cavity walls, loft and floors can have a similar effect of reduced air circulation.

Replacing windows that were drafty will again have a similar effect.

Removal of open fires.

Thick curtains or curtains with blinds or nets fitted close to the windows causing cooler air to be trapped between these and the window.

Open bathroom and kitchen doors.

No extractors in kitchen and bathrooms.

While all of the above help to insulate your home and make it more energy efficient they can help produce a moisture build up. Often windows get the blame for this when condensation shows up on the glass, but this is not the cause of the lack of ventilation can often be the issue. To help combat this, we often recommend the addition of controllable trickle vents when installing windows. This is not always the case as some modern heat exchange systems do not require ventilation.