The planning of air ducts requires careful calculation so that the area of activity of each slightly overlaps that of the next. This system can be used as a substitute for damp courses and can also be applied to old walls without damp-proof courses as a remedy for dampness. Where there is no basement, construction around the base of the wall might include air ducts placed high enough above original ground level to prevent choking by added soil or leaves. Treatment of basements involves avoiding timber floors in houses with basements below soil level and using concrete floors covered with tiles or granolithic paving instead. Vertical damp-proof courses can be installed on the outside of walls, joining horizontal damp courses both above and below ground levels. Rain penetration through brick walls is discussed, emphasizing that good quality bricks and mortar prevent water from penetrating if well put together. Rendering the outside of walls with cement mortar mixed with waterproofing agents or hanging tiles or slates provides protection against dampness. Cavity walls are described as a modern method to prevent damp by building in two thicknesses with a cavity between them, ensuring no ventilation occurs within this space. Rain penetration from roofs is addressed through proper construction and maintenance of chimney stacks, parapet walls, and roof coverings like slates or tiles. Dampness caused by defective waste and rainwater pipes is discussed, advising regular inspection to prevent overflow and choking. Slope requirements for different roofing materials are outlined based on their absorbency and size, with recommendations for lead, zinc, copper, asphalt, and bituminous coverings.
Key Takeaways
- Proper planning of air ducts is essential to prevent dampness in walls without basements.
- Vertical and horizontal damp-proof courses are crucial for preventing moisture from entering the building structure.
- Roof coverings should be properly sloped based on their material type to ensure effective drainage.
Practical Tips
- Use cavity wall construction to naturally separate inner and outer leafs, reducing dampness risks.
- Regularly inspect rainwater pipes for blockages or leaks to prevent water damage inside the building.
Warnings & Risks
- Improper slope of roof coverings can lead to water accumulation and subsequent structural damage.
- Failure to properly install vertical damp-proof courses can result in significant moisture issues within walls.
Modern Application
While many materials and construction techniques have evolved, the principles of proper ventilation and waterproofing remain crucial for preventing dampness. Modern readers should apply these historical methods with contemporary building codes and materials to ensure effective prevention against water damage.
Frequently Asked Questions
Q: What is the recommended slope for a tiled roof?
The pitch or slope of a tiled roof is usually about 45°, as tiles are smaller and less uniform than slates, requiring a steeper angle to prevent water penetration.
Q: How can one effectively ventilate floor timbers in old buildings without basements?
Air ducts spaced at approximately 10 feet centers and protected against vermin entry with terra-cotta or cast-iron air bricks are recommended for ventilating floor timbers.
Q: What is the purpose of a vertical damp-proof course in wall construction?
A vertical damp-proof course, typically made of two layers of asphalt placed on the outside of the main wall and joining horizontal courses above and below ground levels, prevents moisture from entering the building structure.