Property Repair Systems

Settlement Cracks

This project is sponsored by Property Repair Systems

Summary: How to fix settlement and movement cracks that may appear in your home or property.

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If you need help with any type of wall cracking repair problem Property Repair Systems will be pleased to give you completely free, no obligation advice on 01626 336180. The information you need may be in the Project below, but if not call them for expert, unbiased assistance with building products.

Cracks in Walls – are They Still Active?

There are two main types of cracks in walls;

  1. Vertical Cracks – Repair using ‘stitches’ bonded into slots cut across the crack line at right angles, usually in the mortar bed joints. The so-called 'stitches' are usually stainless steel twisted rods and they are bonded into slots with special shrink compensated mortars. The remaining joint and the crack itself is then made good using a soft mortar mix incorporating a shrink proofing agent, to allow the inevitable small remaining movements to be accommodated (See a specialist page on Crack Repair)
  2. Horizontal cracks – usually along the mortar joints

In both cases wall coverings, paint or render may obscure the extent of the cracking, so a Structural Engineer should always be consulted.

It has been known for houses to move suddenly and a few cracks to appear, then stay in that condition for donkeys years. This may be due to a sudden shift in the ground below, or a void in the earth may have suddenly collapsed and filled with soil from above...Any number of geological events could trigger earth movement, but it is the continuation of the movement which should cause concern. Frequently these movements are associated with drainage pipe faults, water mains leaks and collapsing sewers., so always check these items first (See more information on water leak testing here)

Below you will see 3 ways of measuring the movement in a property against an existing crack. These are simple DIY methods of measurement.

However, you can also buy the Professional kit for this job – the Avongard Telltale. (http://www.avongard.co.uk) This clever piece of plastic is called a crack monitoring gauge. It monitors horizontal and vertical movement across a crack on a flat surface to an accuracy of +/-1.0mm and by interpolation to +/-0.5mm. The opening or closing of the crack is then recorded on the monitoring card supplied with each Tell-Tale.

Crack Monitoring Gauge

DIY Methods of Crack Monitoring

Example of a crack in a wall

The image represents a crack down a wall be it internal or external.

Number 1 Is simply a 9 inch by 4 inch piece of 4mm glass with a ¼ inch hole drilled in each corner. Your local glazing merchants can make this for you. They may also be able to provide you with rubber washers to use for protecting the glass when tightening the screws. See our Fixings to Masonry project to attach this to the wall, bridging the crack. Do not tighten the screws too tightly for obvious reasons and take care when fixing, but pinch the glass up carefully to the wall. Any further movement will cause the glass to break. You should then contact a qualified Building Surveyor or Structural Engineer.  Alternatively, the glass strip can simply be fixed with a blob of Araldite at each end, provided that the wall and the glass are thoroughly cleaned.

Number 2 Is a piece of tape stuck over the crack with a pencil mark registering where each end is. If the gap opens the tape will slide across the wall and move away from the pencil lines. If this happens you should call a qualified Building Surveyor or Structural Engineer.

Number 3 Is even easier. You cut a timber wedge and tap it into the crack fairly tightly. Make sure the wood is very dry when you do so. If the crack should open any more then the timber will simply fall out. This method is the least certain as the timber will shrink and expand, as timber does, but used in conjunction with number 2, will tell you if you have movement or not. 
But don't take chances: if you are unsure, contact a Qualified Building Surveyor or Structural Engineer.

Cracks in Walls – How to Repair

Vertical Cracks – Repair using ‘stitches’ bonded into slots cut across the crack line at right angles, usually in the mortar bed joints. The so-called stitches are usually epoxy-glass or stainless steel rods and they are bonded with epoxy or polyester based injection resins. The remaining joint and the crack itself is then made good using a soft mortar mix incorporating a shrink proofing agent, to allow the inevitable small remaining movements to be accommodated (See more on crack repair here)

Repairing Using Stitches

Horizontal Cracks – The chosen repair method will depend on the cause of the crack, but the most likely cause is cavity wall tie corrosion, so replacement of the wall ties will be the primary task, not forgetting isolation of the outer ends of the originals (See more on wall tie replacement here)

Wall Tie

Cracks in Sills and Copings

Cracks in sills can be repaired using chemically enhanced mortars

Many other types of cracks in buildings can be repaired using either chemically enhanced mortars or epoxy materials. For help with these contact Property Repair Systems Their expert staff will be pleased to give you completely free, no obligation advice on 01626 336180.

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