How Much Material Do I Need for External Wall Insulation?

Nearly every phone call we take starts the same way: "I have a wall about so big, what do I need?" Here is how we work it out, so you can do it yourself before you order.

Start with one number

Measure the wall area you are insulating and take off the windows and doors. That single figure drives everything else. For a typical Irish three-bed semi, the external walls come to somewhere between 90 and 120 m2 once openings are deducted.

What one unit covers

Material	One unit covers
Graphite EPS 100mm	3 m2 per pack
Graphite EPS 50mm	6 m2 per pack
Ceresit ZU adhesive, bonding	about 4 m2 per 25kg bag
Ceresit ZU, embedding mesh	about 5 m2 per 25kg bag
Fibreglass mesh	50 m2 per roll
Silicone render CT74	9 m2 per 25kg bucket
Fixings	5-6 plugs per m2

Worked example: 100 m2 of wall

• Boards: 100 ÷ 3 = 34 packs of 100mm graphite EPS
• Adhesive: bonding needs 25 bags, embedding the mesh needs another 20, so 45 bags of ZU in total
• Mesh: 2 rolls, allowing for 100 mm overlaps at every joint
• Render: 100 ÷ 9 = 12 buckets
• Fixings: 100 × 6 = 600 plugs, so 6 packs of 100
• Beads and track: measure your actual corners, reveals and the bottom of the wall rather than guessing

Add about 10% to boards and render for cutting waste and a wet day.

Let the site do the sums

Every product sold by area now carries a calculator on its page. Enter your square metres and it tells you how many units to put in the basket. On the adhesive it goes a step further and asks what you are doing with it, because a bag goes twice as far bonding boards as it does when you are bonding and meshing.

Ordering insulation boards

Boards take up far more space than they weigh, so we price delivery per order rather than charging a flat pallet rate. Place the order as normal and we come back with the exact delivery cost for approval before anything is charged.

Need a hand with your job?

Send us your measurements and we will put together a materials list with prices. Call 085 868 8459, message us on WhatsApp or email sales@all4building.ie. We deliver across Ireland from our Cork warehouse.