A cheaper bag is not a cheaper wall. Divide the price of the bag by the square feet that it covers: that is what your wall costs.
The unbranded plasters that we see in the market cover 14 to 15 sq ft from a 20 kg bag. One 25 kg bag of SIG-MR covers 27 sq ft at 13 mm, measured on site.
| 1,000 sq ft at 13 mm | Bags | Weight to buy and carry up |
|---|---|---|
| SIG-MR, 25 kg bag, 27 sq ft | 38 bags | 950 kg |
| A plaster with 15 sq ft from a 20 kg bag | 67 bags | 1,340 kg |
| A plaster with 14 sq ft from a 20 kg bag | 72 bags | 1,440 kg |
Put the two prices that you were quoted into the calculator on the SIG-MR page. It shows the cost of the same wall with each plaster. Add the transport and the labour for the extra bags.