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Home/Roofing/Plank decking with gaps

Roofing · Homes built before about 1940

Plank decking with gaps between the boards

Old houses were sheathed in planks, not plywood. Modern shingles need continuous support, so new sheathing over the planks belongs in the quote, not in a change order.

Quick answerHouses of this age were sheathed in 1×6 or 1×8 planks rather than plywood. Modern shingles need continuous support and the nails need something to hold. Overlaying plank deck with new sheathing is standard on this stock, and it belongs in the quote, not as a change order once the old roof is off.

This is most common in homes built before about 1940. Plank decking isn’t a defect. It was how roofs were built. It just wasn’t designed for today’s shingles, which expect a smooth, solid surface.

1Why it matters

  • Gaps between boards. Some old roofs were spaced for wood shingles. Asphalt shingles need continuous support underneath.
  • Nails need to hold. A nail that lands in a gap holds nothing. Over time those shingles loosen and lift.
  • Uneven boards. Cupped or warped planks show through new shingles and can stop them sealing flat.
  • Surprise costs. If it isn’t in the quote, it becomes a change order on the day the old roof comes off, when you have the least room to negotiate.

2How to check your deck

  1. Go into the attic with a flashlightLook up at the underside of the roof. Individual boards running horizontally mean plank decking; large sheets mean plywood or OSB.
  2. Look for gaps and daylightVisible gaps between boards, or light showing through, tell you the deck isn’t continuous.
  3. Look for stains and soft spotsDark stains around nails or boards often mean past leaks. Note where they are.
  4. Tell every contractorAsk each one to price new sheathing over the planks so the quotes compare like for like.
Attic safety

Step only on joists or a board laid across them, and watch for nails coming through the deck overhead.

3Fixing it

Do it yourself

  • Confirm plank decking from the attic
  • Photograph stains and gaps
  • Ask for sheathing to be priced in every quote

Hire a pro

  • Tear-off down to the planks
  • Replace rotted planks
  • Install new sheathing over the plank deck
  • Ventilation and flashing while the deck is open

4What drives the cost

New sheathing is priced by the area of the roof, plus any rotted planks that have to be replaced first. Pitch, height and access matter too. Ask for the sheathing as its own line item, with a per-sheet price for extra repairs, so you can compare quotes.

Roofing cost

Planning a reroof over plank decking?

Talk to a roofing contractor who will price the sheathing before the old roof comes off.

877-360-4657

5Questions

Do the planks have to come off?

Usually not. Sound planks are left in place and covered with new sheathing. Rotted boards are replaced first.

Can shingles go straight onto the planks?

Modern shingles need continuous support and solid nailing. That’s why new sheathing over plank deck is standard on houses this age.

Why wasn’t this in my first quote?

Some quotes leave it out to look cheaper. Ask for it in writing up front.

Written by Jaylan Jones. I Like To Exterior Services earns a referral fee when a call connects to a contractor. See our business-model disclosure.

877-360-4657