Key takeaways
- A single-layer privacy fence starts out tight, but thin gaps open between the boards as they dry and shrink.
- Board-on-board overlaps two layers of boards, so the view stays blocked as the wood moves.
- It takes more boards and labour. Our planning range for a 6 ft board-on-board fence is $100–$135 per linear ft, plus HST.
- A 6×6 post has about two and a half times the wood of a 4×4 in cross-section and resists bending and twisting far better.
- Both styles present a nearly solid face to the wind, so posts and rails matter whichever you pick.
A board-on-board fence has two layers of boards that overlap, so you can't see through it even after the wood shrinks. A standard privacy fence has a single row of boards set edge to edge. The single layer is cheaper to build, but as the boards dry, narrow gaps open between them. If you want full privacy for the life of the fence, board-on-board is the better build. If the lowest price matters most, a single-layer fence on sound posts can still do the job.
How each one is built
Both styles start the same way: posts set in the ground, with horizontal rails running between them. The difference is in the boards.
Standard single-layer fence. The boards are fastened to the rails side by side, with their edges touching. From the day it's built, it looks like a solid wall.
Board-on-board fence. The first layer of boards goes on with a space between each one, a little narrower than a board. The second layer covers those spaces, and each board in it overlaps the boards on either side. Looking straight at it, you see a solid face with a layered pattern and shadow lines.
Our standard fence is 6 ft board-on-board with premium boards, on 6×6 pressure-treated posts, with a 2×6 top rail and a 2×4 mid rail.
Why gaps open as the boards shrink
Wood takes on moisture and gives it back depending on the weather. As a board dries, it shrinks across its width, and when it gets wet again, it swells. Pressure-treated lumber is often still damp from the treatment process when it's installed, so the first stretch of warm, dry weather brings the biggest change.
On a single-layer fence, each board pulls back from the boards beside it, and a thin line of daylight opens along every joint. One gap is easy to miss. Dozens of them along a backyard fence let your neighbours see through, especially up close. Boards can also cup or twist as they dry, which widens some gaps further.
On a board-on-board fence, the boards move just as much, but the overlap absorbs it. As long as the overlap is generous, shrinking makes it a little narrower without opening a gap.
Privacy
When both are new, the two styles give similar privacy. The difference shows after the boards have dried out. A single-layer fence becomes partly see-through at the joints, while a well-built board-on-board fence stays closed. If the fence is mainly there for privacy, around a hot tub or patio for example, that difference is the main reason to choose board-on-board.
Wind
Neither style is designed to let air through. A board-on-board fence, like a single-layer one, presents a nearly solid face to the wind, and that push is carried by the rails into the posts and down into the ground. Board-on-board is also heavier, because it puts more boards on the same frame.
That means a solid fence in an open, exposed yard depends on its posts, rails and how the posts are set, whichever board pattern you choose.
Posts: 6×6 vs. 4×4
Lumber sizes are nominal. A 4×4 post actually measures about 3½ × 3½ in (89 × 89 mm), and a 6×6 about 5½ × 5½ in (140 × 140 mm). That gives a 6×6 about two and a half times as much wood in cross-section, and its resistance to bending grows faster than its size, so it flexes far less under the same push from wind, snow or someone leaning on it.
Twisting matters too. Every post moves a little as it dries. A slender post carrying a heavy two-layer fence has less wood to resist that movement and the weight of the boards, so leaning and twisting show sooner. When a post twists, it drags the rails with it, and a gate hung on that post can stop latching. A 6×6 gives the rails, hinges and latches a wider, stiffer base.
Post size doesn't replace good installation. Whatever post you choose, ask how deep the holes will be and what goes around the posts. Those details matter as much as the size of the post.
Materials and cost
Board-on-board costs more than a single-layer fence on the same frame, for clear reasons:
- More boards. Two overlapping layers use noticeably more boards per foot than a single row.
- More fasteners and labour. Every board has to be spaced or lapped and fastened, and the spacing has to stay even along the whole run.
- A stronger frame. The extra weight is a good reason to put board-on-board on a sturdy frame, like the 6×6 posts and 2×6 top rail in our standard build.
Our planning range for a 6 ft board-on-board fence is $100–$135 per linear ft, plus HST. As examples, 50 ft of board-on-board fence came to $5,700–$6,700, and 100 ft of board-on-board fence came to $10,000–$11,000, both plus HST. If you need a lower price, we can build on 4×4 posts instead; that option is priced on request. Our fence cost guide covers gates, removal of the old fence and the site factors that move the price.
Cedar boards are an upgrade on our standard build, priced at the estimate. Our pressure-treated vs. cedar guide compares the two woods.
Maintenance
The two styles need much the same care:
- Stain or seal. It slows weathering and evens out the colour. A board-on-board fence has more board surface, including edges tucked under the overlaps, so staining takes longer and uses more product.
- Keep the bottom dry. Don't let garden soil, mulch or shovelled snow sit against the bottom of the boards. Wood that stays wet is the first to rot.
- Check the hardware. Once a year, tighten gate hinges and latches and look for loose fasteners.
- Replace boards one at a time. A cracked or damaged board can usually be swapped out on either style without rebuilding a section, although on board-on-board you may need to lift the boards that overlap it.
Side by side
| Feature | Single-layer privacy fence | Board-on-board fence |
|---|---|---|
| Privacy when new | Full | Full |
| Privacy after the boards dry | Thin gaps open at the joints | Stays closed if the overlap is generous |
| Boards per foot | One layer | Two overlapping layers |
| Labour | Less | More spacing and fastening |
| Price | Lower | Higher |
| Wind | Nearly solid face | Nearly solid face, and heavier |
| Staining | Less surface | More surface |
Whichever you choose, check the height limit first. A 6 ft fence is about 1.83 m, which fits under the 2 m (about 6.5 ft) backyard limit that Mississauga and Toronto generally allow. Front yards are held lower, and a solid fence doesn't qualify as open construction where a by-law requires it. Our fence height rules guide has the details.
Next steps
See how we build board-on-board fences on our fence installation page, check the planning figures on our pricing page, or book a free on-site estimate to get a written quote for your yard.
Sources
General information, not legal or engineering advice. Rules change and vary by municipality, so confirm them for your property. Prices are planning ranges, plus HST, not quotes.