National Heritage Week: Looking After the Structure of a Period House

Every August, the Heritage Council’s National Heritage Week opens up historic buildings across the country. Many of the most admired are ordinary houses: the Georgian and Victorian terraces of Dún Laoghaire, Monkstown, Rathmines and Bray. StructuralEngineer.ie puts together the structural basics for owners of those houses.

How a period house stands up

Period houses work differently from modern ones:

• Solid walls of brick or stone, in lime mortar that flexes and lets moisture out
• Timber floors whose joist ends sit inside the walls
• Spine walls carrying the floors through the middle of the house
• Chimney breasts back-to-back on the party walls
• Basements whose front walls hold back the street

The five things that cause most damage

1. Moisture in the walls. Blocked gutters, failed downpipes and cement render trap water, and joist ends rot.
2. Cement repairs. Hard cement mortar and render force moisture into the brick, which then decays.
3. Removed structure. Spine walls and chimney breasts taken out by previous owners without support.
4. Lost restraint. Front walls bowing because floors no longer tie them back.
5. Basement “fixes”. Waterproofing or lowering without understanding what the basement walls do.

Before you change anything

• Find out whether the house is a protected structure or in an Architectural Conservation Area. Internal works can need planning permission.
• Get the moisture sources fixed before structural repairs.
• Use lime-based materials for repairs to solid masonry.
• Have an engineer who knows period construction design any opening, tie or basement work.

Find out more

The period property service covers repairs and alterations. Area pages for Dún Laoghaire and Bray go into local conservation rules. To talk through your house, call 01 270 9764.