Clapboard Preparation
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marsha



Joined: 04 Nov 2009
Posts: 1
Location: Nantucket, MA

PostPosted: Thu Nov 05, 2009 9:38 am    Post subject: Clapboard Preparation Reply with quote

I have reviewed several of your clapboard videos which were great but I have several questions remaining.

Hope you can help me with the following:

1. What type and size of nail to use to re-fasten bowed clapboards. I'm not sure if the clapboards are bowed. What I do know is that there is a separation at the overlap. Either I need to fill the gap with caulk and/or add nailing or screws.

2. What type of caulk do I use? There are simply too many choices for me out there. I need to caulk where the clapboards meet the corner trim and potentially in 5% of the clapboard overlaps. As I scrape I am finding a yellow, soft caulk material.

3. What is the recommended sequence of events: do I caulk before I prime?

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johnleeke
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Joined: 20 Aug 2004
Posts: 2924
Location: Portland, Maine, USA

PostPosted: Sun Feb 14, 2010 10:16 am    Post subject: Reply with quote

Quote:
1. What type and size of nail to use to re-fasten bowed clapboards.


Use a steel box nail, hot-dip galvanized (double dipped if you can find them), the length should be the thickness of the clapboards (usually nailing through two clapboards) you are nailing down, plus the thickness of the sheathing boards you are nailing to. If there are no sheathing boards and you are nailing directly into the wall studs, the length is 1.5 times the thickness of the clapboards.

Quote:
I'm not sure if the clapboards are bowed. What I do know is that there is a separation at the overlap. Either I need to fill the gap with caulk and/or add nailing or screws.


Usually it is NOT a good idea to seal the horizontal joints between the clapboards. A little air filtering through these joints helps keep the wall and clapboards dry and free of deterioration. If there are wide gaps, clean out all the junk in the joint and nail the top clapboard back down, usually in new nail holes. Pre-drill through the clapboards so they are less likely to split. Fill the old nail holes with caulk or sealant if the wood around the holes is sound, or with wood-epoxy repair methods if the wood is deteriorated.

Quote:
2. What type of caulk do I use? There are simply too many choices for me out there. I need to caulk where the clapboards meet the corner trim and potentially in 5% of the clapboard overlaps. As I scrape I am finding a yellow, soft caulk material.


Remove all that old caulk, right down to bare wood. Seal the vertical joints with the trim, but do not seal the horizontal joints between the clapboards. Any 100% acrylic sealant that costs at least $5 to $10 per tube will be easy to work with and good enough. A poly-urethane sealant, such as Sonneborn NP1 is more difficult to work with but is more durable that acrylic types.

Clapboard butt joints or overlapped (scarfed) joints may or may not need to be sealed. It depends on the original construction details and current conditions. If you can attach photos to a message here we might be able to advise further on this.

3. What is the recommended sequence of events: do I caulk before I prime?

Overall work sequence:

-- paint removal if necessary
-- clean out all joints
-- surface preparation for painting
-- do woodwork repairs
-- oil-base alkyd-resin primer
-- seal vertical joints if necessary
-- sand lightly if needed to eliminate whiskers
-- spot-prime or full-prime again if bare wood was exposed during sanding
-- two top coats of 100% acrylic house paint

Use lead-safe operations during paint removal, joint cleaning and surface preparation to control the lead-health risk.

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Jeremy Ballard



Joined: 22 Mar 2008
Posts: 127
Location: Providence, RI and Cape Cod, MA

PostPosted: Sun Feb 14, 2010 1:16 pm    Post subject: Reply with quote

Marsha,

I agree with John's advice. The only change I would make would be to use a stainless ring shank nail in exchange for the galvanized nail. 99% of my work is on the Cape and coastal RI, my experience is that galvanized fasteners don't last long in the salt environment. Nantucket being an extreme example.

While I agree that a galvanized fastener that has been painted should have enough protection I prefer to use stainless for all my exterior applications.

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Jeremy
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johnleeke
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Joined: 20 Aug 2004
Posts: 2924
Location: Portland, Maine, USA

PostPosted: Sun Feb 14, 2010 2:26 pm    Post subject: Reply with quote

Stainless steel nails can be good at coastal locations and on clapboards made of old-growth pine or a decay resistant species.

I have repeatedly seen a problem with stainless steel nails when used on new clapboards that are not decay resistant. A fungal decay pocket develops right around the nail, where the nail head has slightly crushed the wood fibers letting water in. This does not happen with the galvi nails because a little of the zinc goes into solution with the water, then soaks into the surrounding wood. The zinc in the wood acts like a preservative preventing decay.

Stainless steel will not be corroded by salt-spray or salt-fog near the coast. By the way, a little salt in the wood acts like a preservative. If there is too much salt in the wood it can form crystals at the surface of the wood that burst the wood fibers resulting in a fuzzy surface and even feathery delamination of the wood. I have seen this cause a problem on unpainted wooden window sash, where there is not much extra wood to begin with.

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Jeremy Ballard



Joined: 22 Mar 2008
Posts: 127
Location: Providence, RI and Cape Cod, MA

PostPosted: Sun Feb 14, 2010 7:59 pm    Post subject: Reply with quote

John,

That's an interesting tidbit of information on the galv. vs. stainless topic. I've only ever installed cedar claps/shingles so I haven't run into the stainless reaction with non-rot resistant species.

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