Exterior paint for 90 ft of smooth fibre cement at 20 ft high, 3 coats
| Paint | 12.11gal |
|---|---|
| What to buybuckets pay from about 3.6 gal up | 3 × 5 gal |
| Wall area90 ft perimeter × 20 ft, less 14 windows and 2 doors | 1,548ft² |
| Spread ratethe easiest exterior surface to cover — closest to interior drywall | 350ft²/gal |
| First coat | 4.42gal |
| Each later coat15% further on a sealed surface | 3.85gal |
| Doubling the first coat would say1.15 gal more than needed | 13.27gal |
- Perimeter
- 90 ft
- Wall height
- 20 ft
- Siding
- smooth fibre cement
- Coats
- 3
- Windows
- 14
Texture decides the spread rate, not the brand
smooth fibre cement takes about 350 ft² per gallon. The same house in smooth fiber cement would take noticeably less, and in brick noticeably more — the mortar joints drink more than the brick does.
90 ft of perimeter at 20 ft high, less 14 windows and two doors, is 1,548 ft². At 3 coat{lop|s} that is 12.11 gallons.
The second coat is cheaper
Once the surface is sealed, paint spreads about 15% further. Doubling the first coat would say 13.27 gal — 1.15 gal more than you need, sitting in the garage until it separates.
Two weather limits matter more than the gallon count
Surface temperature has to stay above about 10 °C for the whole cure, not just while you are painting. A warm afternoon followed by a cold night gives a film that never properly coalesces, and it comes off in sheets the following spring.
Dew point matters as much as rain. Early-morning painting on a clear autumn day fails constantly for exactly this reason — the siding is wet with dew that you cannot see.
Wash first, and wait
Paint over chalky or dirty siding fails at the interface however good the paint is. Pressure-washed wood needs two or three dry days; a moisture meter reading under 15% is the honest test, not "it looks dry".
Back-roll anything you spray
Spray lays paint on the surface. Back-rolling works it into the grain and the grooves. On smooth fibre cement that is the difference between six years and twelve.
Notes
- **Surface texture, not brand, decides the spread rate.** Smooth fibre cement takes about 350 ft² per gallon — the easiest exterior surface to cover — closest to interior drywall. The same house in smooth fibre cement would take 4.42 gal per coat against 4.42 here.
- **Two weather limits matter more than the gallon count.** Surface temperature must stay above about 10 °C for the whole cure, not just while you are painting — a warm afternoon followed by a cold night gives a film that never coalesces. And the surface has to be dry: dew point matters as much as rain, which is why early-morning painting on a clear autumn day so often fails.
- On smooth fibre cement in sound condition, spot-prime bare and repaired areas rather than priming the whole wall. A full prime coat here buys very little.
- Wash it first, and let it dry properly. Paint over chalky or dirty siding fails at the interface no matter how good the paint is, and pressure-washed wood needs two or three dry days before it is ready — a moisture meter reading under 15% is the honest test.
- Back-roll anything sprayed. Spray alone lays the paint on the surface; back-rolling works it into the grain and the grooves, and on smooth fibre cement that is the difference between six years and twelve.
- Buy it all at once and box it. Exterior walls are seen in full sun from a distance, which is the least forgiving lighting there is for a batch difference.
Nearby sizes
- Exterior paint for 80 ft of smooth fibre cement at 20 ft high, 3 coats
- Exterior paint for 100 ft of smooth fibre cement at 20 ft high, 3 coats
- Exterior paint for 110 ft of smooth fibre cement at 20 ft high, 3 coats
- Exterior paint for 90 ft of smooth fibre cement at 18 ft high, 3 coats
- Exterior paint for 90 ft of smooth fibre cement at 10 ft high, 3 coats
- Exterior paint for 90 ft of lap siding at 20 ft high, 3 coats
- Exterior paint for 90 ft of shiplap siding at 20 ft high, 3 coats
- Exterior paint for 90 ft of smooth fibre cement at 20 ft high, 2 coats
- Exterior paint for 90 ft of smooth fibre cement at 20 ft high, 1 coats
- Exterior paint for 90 ft of smooth fibre cement at 20 ft high, 3 coats
- Exterior paint for 90 ft of smooth fibre cement at 20 ft high, 3 coats
- Exterior paint for 90 ft of smooth fibre cement at 20 ft high, 3 coats
Read more
- Paint Coverage on Stucco and Brick: Why the Gallon Goes Half as FarA gallon rated at 400 square feet covers 150 on heavy stucco. The rating is honest — the wall simply has three times the surface a flat wall does.
- Cost to Paint Exterior Siding by Material and Story CountExterior prep is half the invoice and the entire reason one job lasts twelve years and the next one peels in three.
- Spray or Roll Exterior Paint: Speed, Extra Material, and Why Back-Rolling MattersSpraying is three to four times faster and uses a third more paint. Neither of those is the important number — the important one is whether the film keys into the surface.
- Paint the Siding or Replace It: The Twenty-Year ComparisonPainting is a quarter the cost and lasts a fifth as long. That makes it close on money and decisive on everything else — as long as the substrate underneath is sound.