Plastic Battens? Metal Battens? Wood Battens? What is a Batten? Which should I use?
A batten is an approved strip of wood no less than 1″ thick and 2″ wide and typically 4 feet long. These are installed on the roof horizontally. Most tiles have a lug or an anchor on the back of them to hook to the batten. The nail holes are lined up on these tiles for the nail to be driven directly into the batten strip. Typical wood battens are nailed to the deck 24″ on center with 8d nails or 12″ on center with staples. See local building codes or TRI book (july 2006 page 20 detail MC-04) for details.
Batten layout is a key to a beautiful tile roof. Correct batten layout ensures proper tile spacing and avoids short courses of tile or over exposed courses of tile in the roof. The major concern is over exposure which is a major cause of leaks, and a classic way for shady roofers to save money on time and materials by over exposing courses. All battens are to be laid out so the tile that is being used has a minimum 3″ head lap on the tile, or the head lap as per the tile installation instructions. Not all tiles have the same head lap but industry standard for most tile roofing is 3 inches. All battens raise the roof tile off the deck, creating an air space between the tile and the deck. Studies have shown benefits in energy efficiency with a batten application.
Wood Battens: Typically 1″x2″x4′ consisting of redwood or cedar. These are the typical battens used on tile roofing.
Approx. penetrations per square: 110 – 198*
- They are cost effective and are an industry staple. When fastened down they are a tried and true method of holding roof tiles in place.On wood battens the concrete tile can hook to the batten and be nailed into the batten for 3/4″ penetration into the batten which is code to fasten tiles to the deck. (See Table 1B in TRI book 7/06 page 10) This can dramatically decreases the amount penetrations put in the underlayment when installing the tile over wood battens.
- Wood battens are installed with a gap at least every four (4) feet, so if water finds it’s way to your underlayment the water runs along the batten to find a gap in the batten so it can flow down hill and off the roof.Water should rarely if ever touch your felt paper and have to flow around battens to get off the roof. When a tile roof is properly installed with proper flashing’s made specifically for the tile; rain water should almost never go under the tile and onto the felt paper. That should be a rare occurrence such as when there is an overwhelming rain, excessive winds, or debris etc… and is usually isolated to a specific section of the roof where special caution or maintenance is needed.In moderate climate areas such as Sacramento California there may be less concern, and building codes may require minimum applications because it is less likely that water gets under the roof due to driving rains.
(Picture Above: S-Tile installed over wood battens.)
Plastic Battens – made of plastic. Approx. penetrations per square: 286*
- Fluted channels in the batten allow water water to run through the batten and down the roof. Fluted design allows air to circulate under the tile. Non-porous and will not absorb moisture.
- Plastic battens can have up to double the penetrations.Per the instruction manual – plastic battens are to be fastened every 6″ with a staple fastener, where as, wood battens require a fastener every 12″.Wood battens are an approved anchor for tile, hence, a roof tile can be fastened to the batten alone and the nail used to hold down the tile does not have to penetrate the felt paper. Nails used to fasten tiles to plastic battens require the nail to penetrate through the plastic batten and into the deck to be securely fastened to the structure when required. For more information on nailing and penetrations see:
TRI/WSRCA ICC-ES ESR-2015P Table 1A & Table 1B
TRI/WSRCA ICC-ES ESR-2015P MC-04
ICC Evaluation Service Report (Plastic Battens)
Elevated Battens(Counter Battens) – typically made of treated wood, they come in lengths of 1″x2″x4′, 1″x3″x4′, 1″x2″x8′. Approx. penetrations per square: 110*
- Elevated battens are your standard wood battens but they have a wood or plastic block attached to them approx. every 12″ or so as per nailing requirements to hold them up off the deck. This creates an additionally increased air space between the tile and the underlayment which improves energy efficiency. How? Take a look at the MonierLifetile Elevated Batten System Flyer.
Elevated battens are fastened with the same specifications as wood battens. (specific nailing information is in the TRI/WSRCA ICC-ES ESR-2015P) They are an approved tile anchor and tiles can be nailed directly in the batten as an anchor. They allow air flow under the tile roof which helps keep the underlayment dry from natural moisture in the air, and prevents the direct transfer of heat from the roof tiles to the deck into the attic. The air space between the tile and the deck is an effective heat barrier(or natural insulation).
- The only slight downside is the price. Elevated Battens are more expensive than other battens on the market. You will have to weight out returns on energy savings, and over all peace of mind by installing these.
Tile roofing is time tested with no battens, with wood battens, with felt paper, with no felt paper etc…. How have tile roofs worked with and without battens, and with and without underlayment? For the most part, proper overlaps on the tile, and proper metal work.
With the proper installation of the tile, and metal flashing’s that are built to control high volumes of water – very little (if any) water should ever go under the roof tile.
Battens are an excellent material used by the roofing industry to help secure the roof tiles, keep the tile courses straight, create energy efficiency, and reduce labor costs.
*Approx. Penetrations per Square
A penetration is how many fasteners that penetrate the underlayment.
Penetrations per square are based off a 10’x10′ roof area = 1 square. Approx. twenty-two (22) four foot long battens are needed to roof a square. Approx. 4 roof tiles per batten and one nail per tile. Wood battens require 5 fasteners (1 fastener every 12″) per batten, and plastic battens require 9 fasteners (1 fastener every 6″) per batten. The variance in the wood batten # is due to the tile nail size. Tile nails do not need to penetrate the underlayment in order to attain 3/4″ penetration into the wood batten and be securely fastened per code. Depending on what type of nail is used by the roofer the penetrations can be substantially more or less in wood battens.