Ventilation and airbricks

The short answer

Ventilation removes the moisture a household generates and keeps timber floors and roof spaces dry. Extract fans in kitchens and bathrooms, trickle vents in windows, airbricks at ground level and ventilation in the roof space all have a job to do. Blocking airbricks — often during landscaping or insulation work — is a common cause of damp and rot in suspended timber floors.

What the work involves

Fitting or upgrading extract fans, adding trickle vents, clearing or reinstating airbricks, ventilating disused flues, and ensuring roof space ventilation is not blocked by insulation pushed into the eaves.

Rules and consents in Scotland

New extract ventilation should meet building standards ventilation rates. Altering an elevation on a listed building to add a vent or fan outlet can need consent. Blocking existing ventilation is not usually a breach in itself but often causes a repairing standard problem in rented property.

What commonly goes wrong

Pushing loft insulation tight into the eaves and blocking the airflow path, which causes condensation on the underside of the sarking.

What it usually costs

Indicative ranges only, to help you judge a quote. They are not an estimate for your property — only the business doing the work can give you that.

• Clearing blocked airbricks is a very low-cost job with a disproportionate benefit.
• Humidity-sensing extract fans are inexpensive and cheap to run.
• Trickle vents retro-fitted to existing windows are a modest cost per window.
• Positive input ventilation or mechanical ventilation with heat recovery costs more and suits airtight properties.

What to do, in order

1. 1Walk the outside of the property and count the airbricks; clear anything blocking them.
2. 2Check that raised paths, decking or planting have not buried ground-level vents.
3. 3Test extract fans by holding a sheet of paper to the grille.
4. 4Vent any disused flue at both top and bottom.
5. 5Check loft eaves are clear of insulation.
6. 6Re-check after any landscaping or insulation work.

Local detail for the Lothians

• Edinburgh garden-level and basement flats commonly have airbricks buried by later paving or raised planting beds.
• Suspended timber floors are near-universal in pre-1919 Lothians property and depend entirely on underfloor ventilation.
• Sealed disused fireplaces in period flats remove ventilation the room was designed around.
• Airtight new flats in Leith and Livingston rely on mechanical ventilation systems that need filters cleaned to work.

When you need a professional

A builder or property maintenance contractor for airbricks, an electrician or ventilation installer for fans and systems.

Common questions

Why shouldn't I block airbricks?

They ventilate the void under a suspended timber floor. Blocking them raises humidity under the floor and can lead to rot.

Can I fit a fan in a listed building?

Often, but the external outlet is the sensitive part and can need listed building consent.

Related pages

• Condensation and mould

  Ventilation, heating patterns and cold spots — the most common damp complaint.

• Insulation and draughtproofing

  Loft, floor and wall insulation in hard-to-treat Scottish buildings.

• Rot and timber decay

  Wet rot, dry rot and woodworm in Scottish timber floors and roofs.