New roof

Old 09-07-04, 11:02 AM
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New roof

I am having a house built by a company that contracts the entire home build project. Today I went to look at the progress on the house, and it looks as if the roof is ready to be papered and shingled. However, from the inside looking out I can see some large gaps between the plywood sheets in the roof. as an example, at the peek of the roof, there is about a 2 inch gap where I can see the sky through, other gaps are betweet sheets about half way down the roof. I do not think that this is right... I mean, these aren't for roof vents or anything like that, there are cut outs for the roof vents, it just looks to me like they ran out of plywood for the roof, and started spacing the plywood further apart... Does anyone have any reccomendations?
Old 09-07-04, 01:48 PM
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Call the builder and ask him why its like that. Only reason a gap should be visible at the ridge is for a ridge vent.
Old 09-07-04, 02:05 PM
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Thanks so much for the response.. I talked to the builder about the gaps, and he said that it was OK like that...I am looking for another opinion...

I think that I am going to take some pictures of the roof the way that it is so that I have some documentation in case I need it.
Old 09-08-04, 12:39 PM
kent hodgson
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Cool Decking Gaps

Any gap over 1/4" is too extreme. Depending on conditions, leaving a small even gap between sheets of decking is acceptable. For instance: if the decking is extremely dry you may leave a small gap to allow for expansion although it shouldn't be necessary if the roof is properly ventilated. I would suggest leaving the slot at the ridge and use ridge vent and closing up the other holes. Any vent below the peak allows hot, moist air to collect at the ridge as well as only allowing "Zonal Venting" of the roof. Continuous ridge vents are the way to go.
Old 09-21-04, 07:16 PM
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Gaps between rows of plywood are necessary. If your roof structure is done with trusses then chances are they are 2 feet on center. Plywood clips are required between the trusses. They are usually silver since they're aluminum. So you should see silver "tabs" when looking up at teh roof from inside and they should extend over both the lower row and the row above it.

These plywood clips are designed to gap the rows of plywood about 1/8 inch. Now this is necessary becasue wood expands due to moisture and thus the gaps give the plywood room to expand. If not then when the plywood expands you end up with a buckled roof.

Now what may appear to be a 2 inch gap may in reality be much less. When light traverses through a hole it expands and thus the gap looks much bigger than it actually is.

Try this. Cut a small hole in a piece of paper or card board. Put a flashlight on one side of the hole. walk back maybe 10 feet and you'll see that the hole looks bigger than it actually is.

Now the reason the gap at the top looks bigger could be 2 reasons. If a ridge vent will be installed then naturally the plywood will not go to the peak.

The 2nd reason is that the last row of plywood was an inch or so short of the peak. Putting another 1 inch strip to got to the top of the peak would be a waste. This is because at the top there will be no load for teh roof sheething to carry for such a small dimension. The shingle caps will cover this. A shingle cap is just one of the 3 "squares" that make a shingle. A shingle is cut into 3 pieces at the "grooves." So the shingle cap will extend down each side about 5-6 inches.

So a bigger gap at teh top is actually better in that it will have more room to expand and also create an infiltration point to help with keeping air movin in the attic. this maybe minimal but the key to keeping your roof dry is air movement.

If yopu do a google on cedar shake roofs and look at how those roofs go on you'd be amazed at the gap between the sheathing rows. This "excessive" space is necessary to keep the cedar shakes dry.

Once we built a house and had the home owner's wife go ballistic on us when she saw the gaps between the rows of plywood. We tried to explain to her what was happening. We showed her the plywood clips and how they space teh rows. She continued calling us a bunch of incompetent idiots lol. She went to the builder and he came back and started laughing at her after seeing what she was ragging about. Her husband understood and we just gave him our sympathies for having to live with her lmao.

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