Repairs: roofs and rainwater goods

Problem 21: Water penetration at wall abutments with roofs

This is very common, and is usually the result of basic detailing errors.

Solution

Where parapet walls are involved, it is essential to check the workmanship. There is plenty of scope for lack of attention to the right details in this area.

Ensure the contractor is aware of Building Regulation requirements and of good practice details such as those in Rolled Lead Sheet – The Complete Manual published by the Lead Sheet Association.

On-site supervision by the surveyor in areas such as this can more than pay off in terms of saved hours later trying to inspect and resolve the problem after the scaffold has been removed.

New build; new waterfall

The author recalls a particular problem on a new-build new roof where there was a backfall in the felt under the tiles before it dropped into the parapet taper gutter (sometimes wrongly called a ‘box gutter’). This discharged onto the internal wall of the parapet some 100mm (4 inches) deep. It was just waiting to fill up with water before it eventually poured back into the building.

A complete re-roof was the only solution, because the levels of the roof sheeting and battening were completely wrong.

The roofing contractor was extremely resistant, nevertheless re-roofing was the only solution in the end. In this case, it helped that the client was prepared to litigate.

COST SEQUENCE - Roof eaves felt repair

Supply appropriate access. Ladder or scaffold tower assumed for pricing purposes, 2-storey height assumed. Assumed eaves run of 6m.

  1. Carefully strip back lower 2 no. courses of tiles at eaves and set aside for reuse.
  2. Carefully cut back defective roofing felt at eaves lap into gutter.
  3. Allow for breaking out of the lowest roofing/tile batten.
  4. Install propriety u-PVC eaves of flashing detail spiked to top face of rafters and re-dress original felt over lap.
  5. Reinstate new lowest tile batten.
  6. Re-set 2 courses of tile to original guage.

Roof eaves felt repair - COST £390

Small works pricing

Since the original price estimating in 2008 the economic turmoil of the last few years has caused some disparities in pricing - if you are reviewing these figures in the London area they may look laughable - if you are located in Hull they might still look a bit expensive. Please treat them with caution and of course always consider obtaining more than one quote against which to test prices. Reference to the BCIS or a small works pricing book such as Spons or Laxton's will help assess costs and the hourly labour rates upon which they are based.