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Question DetailsAsked on 5/13/2017

Crack in Ridge Board

During a recent inspection, a 4' lengthwise crack was found in the ridge board (not beam). Before entering the attic, one of the inspectors had been on the roof, and said there was no sag, and that he hadn't been able to feel that there was any issue with the ridge board when he had walked over that section of roof. One of the inspectors recommended a structural engineer, while the other said that wasn't needed and to contact a framing contractor. We got a quote from a structural engineer to come out, but we'd rather not spend the extra money if it's really not needed. My reading seems to indicate that a ridge board is not structural, and is only used to make initial framing easier. If that is the case, is a crack really something to be concerned about? The only contractor we've gotten to return our calls so far didn't really inspire confidence.

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1 Answer


Here is a link to a pretty clear article on ridge board versus beam -

Assuming your roofing framing is a truss system - looks like truss bridge construction like below with substantial metal plate connections (or sometimes wood pins if exposed cathedral ceiling) at all intersections -

or you have full-width ceiling joists or steel tension rods across the house which are tied to the lower part of the rafters at each side (or rarely intermediate tension or collar ties higher up as per article, sometimes both) with metal brackets like this -

then the ridge board is likely not a "beam". If it is a cathedral ceiling without cross members or truss framing, or the ridge board has vertical supports under it (including a post or header under it in the gable endwalls, and probably intermediate supports too aqt least at splices along the ridgeline) then it is certainly a structural beam. Ditto if the rafters sit on top of it rather than tying into the side of it. If there are no horizontal members across the house holding the bottoms of the rafters from splaying out (pushing the tops of the walls outward) then it would be a beam - and framing brackets holding the rafters at the walls do NOT count as horizontal restraints.

Also, generally, a ridge "board" would be 2x dimensional lumber just like the rafters - a "ridge beam" would almost always (unless supported by a lot of posts) be 4x wide and in modern construction most commonly a laminated beam or sometimes a plywood-webbed wood girder, and commonly (but not always) deeper than just the rafter contact area.

If there are horizontal ties/attic floor joists, and the board is just a piece of 2x as tall as the incoming rafters (commonly 2x6 with 2x4 rafters, or 2x8 with 2x6 rafters), with the rafters fastened into it and directly opposing each other like this - 3rd photo in article -

and no separate vertical supports under it, then it is most likely a ridge board as you say, not a beam. If the rafters are NOT directly opposed on each side of it, then it is considered a beam and a structural member. Ditto (generally) if the roof slope is flatter than a 3:12 slope (3 inches rise per horizontal foot of run) - though depending on the rafter and bottom tie design that break point can be flatter or steeper if specifically designed for such.

Either way, it is part of the structural framing system so is "structural" by definition even if not a "structural beam" - not only because of that, but it also is intended to prevent twisting of the rafters and also provides end-sway resistance when the rafters are properly fastened to it with joist hangers, not just toenailed into it.

Assuming it is a "ridge board" rather than a structural lead-carrying beam, a wood drying shrinkage crack running partway along the length of it would not be a major concern in and of itself. If significant or opening with a visible opening though the board, or there is significant visible tearing of the wood fibers or the crack is angling crossgrain, it might indicate the rafters are not bearing on it evenly or the roof is tilting endwise or to one side, which WOULD be a structural issue.

Since you did not get a warm fuzzy feeling with the one contractor, and one inspector did recommend getting an engineer out, I would have a Structural Engineer look at it rather than risk it - probably about $300 plus or minus $50 for a site visit including a letter report or minor letter design note - plus any needed design cost if it is more serious. If he judges it to be just a shrinkage crack, he may say leave it. Personally for that length crack even if not a sign of structural failure I would at a minimum recommend that Simpson nail-on timber plates be put on each side of the ridge board along the crack length to stop the cracking and reinforce it. And for this sort of application, should always be nailed on even if a spiked timber splice plate design like following is used, because if not factory installed in a truss press they tend to work their way back out if not nailed with Teco nails -

Be sure the structural engineer sends you a written letter report (commonly would be about 1/2 page in this case, plus a photo of the crack, if he is recommending nothing or just a truss plate repair be done).

If it IS significant and the board needs replacing, it is not simple - typically a $1000 job or so, because temporary supports need to be put in to spread the rafters apart and hold them there while the ridge board is removed and replaced - which may involve typically 5-8 rafters being held apart during the replacement of the board. Or, if NOT a structural beam and not requiring removal, a steel plate or sistering (nailing on additional ridge board or plywood pieces) on each side between the rafters may be the recommended solution, depending on the particular circumstances. But be sure the engineer puts the fix in writing and that it is done per the drawing/spec, so come resale time you have proof the fix was professionally done and approved.

In most areas, since a structural repair, if the piece needs to be removed should have a building permit for it - generally not if just putting on cover/reinforcing plates.

Note if any sort of cover plate or reinforcing is done, the design should note a specific fastener type and spacing - make sure the contractor does it that way, because they tend to not follow the instructions - using regular 16d nails rather than structural fasteners, or using a wider spacing on the nailing than specified.

And if a wood coverplate is done, discuss with engineer if that is going to necessitate taking your ridge vent off (if you have one) and widening the opening in the plywood to allow adequate ridge vent ventilation - not a problem with steel plates, maybe with plywood overlays, certainly with 2x overlays, which might necessitate wider ridge vent too - so the prefernece would be to steel plates or thin plywood overlays versus 2x pieces scabbed on to avoid having to mess with the ridge vent - assuming you have one.

Repair cost - can't really say without seeing it, but if just metal mending plates are called for, probably about $50-100 materials (depending on whether he buys them individually at Home Depot or in contractor 80-100 packs - you will need about 20 of them if using those, in commonly available 6" length) and maybe $150-300 labor depending on whether you have an individual Carpenter or a General/Framing Contractor do it. Similar cost for plywood or common lumber repair - materials cheaper, labor a bit more with the cutting and handling into the attic.

Bottom line,since you re not sure if a significant problem or not, and since one inspector said it should be looked at professionally, I would fix it for peace of mind, and to avoid issues come resale time. And having a structural engineer's letter report or design on it covers your tail in that case on the repair.

Answered 3 years ago by LCD

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