Buyer's guide / Mesh and nets

Fibre Mesh for Plaster: Control Cracks Where Brick Meets Concrete

Why plaster cracks along beams and columns, and how fibreglass mesh tape can help control it. Width, where to fix it and how to apply it. From an Indore mesh stockist.

Fibreglass plaster mesh rolls stacked at the counter

Published 16 Sept 20263 min readHM Ibrahim & Co, Siyaganj, Indore, since 1939

Fibre mesh rolls at the Siyaganj counter.

Look at the plaster on any building in Indore. Find the line where a brick wall meets a concrete beam or column. If there is a hairline crack running along it, you have found the most common plaster fault there is.

It is not bad workmanship. It is physics. A strip of fibre mesh, specified and fixed properly, can help control it.

Why the crack appears

Brick and concrete expand and shrink at different rates with heat and damp. Where they meet, they move against each other. Plaster that bridges the joint is stretched, and it cracks along the line.

The crack repeats on every joint in the building, which is why it looks so systematic.

White fibre mesh rolls standing in a row

What fibre mesh does

Fibre mesh is a net of glass fibre coated to resist the alkali in cement. Embedded in the plaster, it spreads the stress over a wider strip so no single line takes the full pull. The plaster still moves, but the mesh can help keep that movement from opening into a visible crack.

Where to use it

At brick and concrete joints: beams, columns, slab edges.
Over conduit and pipe chases that have been cut and filled.
At corners of windows and doors, where diagonal cracks start.
Over whole walls in thin plaster, in the form of a wide mesh.
On ceilings where hairline cracks appear after the pour.

Fibre mesh rolls beside GI wire mesh in the godown

Which width

Width	Typical use
4 inch	Narrow joints between brick and concrete
6 inch	Beam and column joints, most common
8 inch	Wide chases and corner reinforcement
1 metre	Full wall or ceiling reinforcement

How to apply

Clean the joint and wet the surface.
Apply the first coat of plaster, about two-thirds of the final thickness.
Press the mesh into the wet plaster, centred on the joint, with at least 2 inches of overlap on each side.
Cover it with the second coat so the mesh is fully buried.
Finish the surface in the normal way.

Do not leave the mesh on the surface. A mesh that sits on top of the plaster does nothing and shows through the paint.

Self-adhesive tape or plain mesh

Self-adhesive tape is quick for dry joints and for plasterboard. It sticks to the wall.
Plain mesh is pressed into wet plaster and is the choice for sand-cement plaster.

For brick and concrete in Indore, plain alkali-resistant mesh in plaster is the usual choice.

Quality check

GSM: heavier mesh, such as 145 gsm, is stronger than 45 gsm. Ask for the weight per square metre.
Alkali resistant coating: a mesh without it breaks down in cement within a few years.
Weave: even and tight, not loose.

See fibre mesh for the widths in stock.

FAQs

Does fibre mesh stop all plaster cracks?
No. It can help control cracking when specified and installed appropriately. It does not eliminate every joint-movement crack, and it does not fix structural movement or a poor plaster mix.

What width fibre mesh for a beam?
6 inch is the usual width, with 8 inch for wide joints.

Is fibre mesh the same as wire mesh?
No. Fibre mesh is glass fibre, light and rust free. Wire mesh is steel and used for heavier plastering such as chicken mesh on timber.

Can fibre mesh be used outdoors?
Yes, alkali resistant mesh embedded in cement plaster is used on external walls.

How much fibre mesh do I need?
Measure the total length of beam, column and chase joints. Add 10% for overlap.