Soffit boards form part of the roofline, along with fascias, bargeboards and guttering. To prevent a build up of condensation (usually in winter) within the loft and eaves space, some form of ventilation is usually required.
This page explains the most common form of ventilation – soffit vents. It also contains a few other options for you to consider, depending on your type of roof.
The ventilation options available will depend on the type of soffit boards you have:
New Plastic Boards
If you have (or are looking to install) new plastic Upvc boards to your roofline then there are two options to vent them:
Option 1 – Pre-drilled vents/slits. These soffit boards are made with vents already cut into the board. They meet all building regulations and are the easiest way to vent a new Upvc roofline installation. This type of vent is the least attractive as they attract dirt, cobwebs and insects, they are also visible from ground level. See the photo below:
Option 2 – Install a plain soffit board but without the pre-drilled vents. Instead a fascia vent can be fitted, this is hidden from view by the guttering so looks much nicer and less obtrusive than the pre-vented soffit board. I always use the over fascia vent as it also meets building regulations, see the photo below:
If you are looking to vent existing timber soffits then the best option would be to either trim down the fascia and install a 10mm vent as described above(that’s hard work by the way) or install some circular vents. You will need to a buy a circular hole saw for your drill, making sure the size is the same as vents (usually but no always 68mm). This option is one of the least attractive as the vents can be seen from ground level and attract dirt cobwebs etc. You can purchase the 68mm vents here.
Many soffit boards in the United Kingdom are made from a mixture of asbestos and cement. These boards are harmless provided they are not cut, drilled or sanded as this produces asbestos dust. One should never cut holes into these boards for circular vents. If you have brittle thin cement-like boards on your roofline then chances are asbestos.
The 68mm circular vents can be purchased from Amazon here. You will need to buy a suitable hole saw for a drill as well.
There are other options for venting a roof or eaves, see this page or the photo below: