Real estate

ASK THE CARPENTER

Repairing a carport and slate roofs

HANDOUT
The beam supporting the midsection of the carport at this reader’s home has rotted.

Q. I have a carport on my house (a low-slope atomic ranch-style home), and the end of the beam supporting the midsection has rotted off. The rot was hidden by wrapping it in tin to match the fascia board. I’m wondering whether I can cut back just beyond the upright support and stagger the joints to repair the beam. Then I would replace the upright with a 6-by-6 (with a temporary support beside the beam while this is happening, of course). The beam is made up of four 16.2-by-10-foot boards. Thanks for any advice.

G.L.

A. All splices should be over a vertical post. If you’re going through the trouble of putting in a new vertical post and temporarily supporting the roof, then you should replace the entire beam with full-length framing members and skip the splicing. It’ll be faster than trying to cut back and splice stuff back in.

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Before doing anything, renail the existing lapped rafters together with 12d galvanized nails. For a nail-fastening pattern: a 2-by-10 beam should have a minimum of four 3-inch nails fastened in a vertical pattern from both sides of the beam every 16 inches on center. Be on the safe side: When in doubt, use extra nails; having too few can result in diminished holding strength that could allow the beam to separate. I sometimes use HeadLok structural screws for situations like this and install them with an impact driver. The HeadLoks will draw the two rafters tighter together than the nails will. Follow the same fastening pattern.

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Use nipper pliers or a reciprocating saw and metal blade to cut away any nails from the rafters above. (You might even be able to bang them up and remove them.)

Try to use very straight lumber and build the beam on a flat surface or on top of sawhorses to keep the corners aligned. When working with an extraordinarily heavy beam, I usually install things in sections to make lifting easier. If this is the case, make sure the splices fall over the top of the support posts. Use temporary posts to hold and support your progress.

Once the new beam is installed and supported properly, add hurricane ties to every rafter. The connectors secure the rafters to the new beam. I use Simpson H2.5 for situations like this.

HANDOUT
Ice and snow falling from the second story damaged these roof slates.

Q. I have a somewhat unique issue with a section of roof that I’m hoping you can help me sort out. Our condo in Cambridge is in a slate-roofed house that was built in 1888. There is a small first-floor bay jutting out from the back of the house on the north side that was added on some time later, also with a slate roof. It receives a lot of falling ice and snow from the second-story roof. It also sends small cascades of snow tumbling into the driveway below, which can be hazardous.

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Several of the slates, especially the bottom course, are now cracked and broken from the brutal winter of 2015. The estimates we’ve gotten to reroof with asphalt shingle have been much more expensive than the estimates to reroof with our own slates, which seems strange to me. I’m also concerned that asphalt shingle won’t be able to withstand the impact of snow and ice falling from above and that it might lead to moisture and ice dam problems, which we’ve never had. Even in its current condition, the roof is not leaking into the house. Is it possible we can get a simple repair to the slates and flashing, or is reroofing really needed? And could asphalt potentially retain snow to the point of causing moisture to build up and back into the wall behind it?

Thank you so much for your time and keep up the great work.

ANNIE RAINES

A. Thanks for reading, Annie. You should be able to find a company to replace the existing slate shingles and flashing. Ask the roofing company to install snow guards to prevent falling ice. Snow guards hold snow or ice in place on the upper roof, so it can melt completely or drop off in small amounts. Regarding your question about asphalt shingles: You are describing what ice dams do. Proper insulation prevents ice dams.

Rob Robillard is a general contractor, carpenter, editor of AConcordCarpenter.com, and principal of a carpentry and renovation business. Send your questions to homerepair@globe.com or tweet them to @robertrobillard.