Carpet grippers are narrow strips of plywood with rows of sharp pins that face upwards.

The pins are angled at 65 degrees to the horizontal, and are designed to grip the carpet quickly and firmly when it is stretched into position and placed on top.

There are two main types of carpet gripper:

• domestic carpet gripper - which has two rows of pins
  
  
• commercial carpet gripper - which has three rows of pins and provides a more secure hold on stiffer carpets.

The carpet gripper is installed before you lay the carpet, with the pins facing towards the wall or outside edge of the carpet.

The most common length is 1.220 metres (4 feet).

You can cut these pieces into shorter lengths when finishing against a wall or going around corners.

The lengths can be cut using gripper strip cutters.

Fixing to the subfloor

Most grippers have steel nails positioned at regular intervals along the length of the plywood.

When you put the gripper in position on the floor, you can then simply hammer the nails in to secure the strip.

There are different types of nails used for different subfloor materials:

• ring shank nails are designed for timber or plywood subfloors
  
  
• smooth shank nails are designed for higher density (harder) concrete subfloors
  
  
• spiral shank nails are for lower density concrete, which tends to crumble more around the nail hole.

In areas where it is too difficult to use the pre-nailed gripper, 'no nail' or 'standard' carpet gripper is used.

In this case, the gripper strip can be fixed to the floor surface using contact or construction adhesive.

For surfaces such as ceramic tiles, it can be fixed using plugs and screws.

If the subfloor is metal, you can use self-tapping screws.

Also note that on thinner carpets you can use a 'short pin' gripper, which helps to avoid the problem of the pins penetrating too far into the carpet and being felt by bare feet walking over the top.

The gully

The gripper strip has an undercut bevel on one side which is placed facing the wall.

This gives you a space, or gully, to tuck the edge of the carpet into.

The width of the gully should be about 60% of the thickness of the carpet.

Don't make the gully too wide, because that will cause the carpet to droop at the edge.

Over time, the carpet could also unhook from the pins and loose its tension

Also don't make the gully too narrow, because then you won't be able to tuck in the edge of the carpet.

If you try to wedge or force the carpet into position, you might end up cracking the skirting board.

Curves and corners

When you're working around curves, doorways and other odd shapes, you still need to maintain an even gully width.

Make sure you secure each piece with at least two nails.

This will stop the piece from spinning or turning when you push the carpet edge into the gully.

If you need to get under kickboards or into other awkward places, you can use a drive bar and heavy hammer to drive the nails into the subfloor.

Calculating quantities

The most obvious way to calculate the amount of gripper strip needed for an installation is to measure around the perimeter walls, not including doorways and other openings (unless the carpet is butting up against a different floor covering).

However, carpet layers sometimes use a simple rule of thumb to estimate the quantity needed:

For residential installations: allow 0.81 lineal metres for every square metre of carpet

For commercial installations: allow 0.65 lineal metres for every square metre of carpet.