# Installing fiber cement siding over existing siding



## elsobrider (Aug 3, 2010)

I have existing tongue and groove type 5/8" wood siding. There may not be any felt paper underneath as the house is 60 years old. I was thinking i could put new felt over the T&G and put the new fiber cement siding on top of that. Basically using the old siding as my shear wall and avoiding a tear-off. I was also going to remove the bottom strip of existing siding just to inspect for rot where all my studs are sitting on the sill plate.And if there is rot abating the rot and repairing the studs/sill where needed and replacing with new plywood. Also i live in a temperate climate. No freezing in the winter or sweltering heat in the summer. Does that sound like a good plan?


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## Just Bill (Dec 21, 2008)

I don't like the idea of installing any new siding over old siding. It makes finishing around opening look bad. And with the old siding removed, you can see any areas that need repair and properly wrap with a moisture barrier. There should be sheathing under the old siding, if not, do that also.


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## Grampa Bud (Apr 6, 2009)

All of what 'Just Bill' said plus... if your home is 60+ years old it probably lacks insulation; it probably has out-of-date wiring, and may have other code problems that could be fixed by removing the old siding and inspecting one wall at a time.


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## Scuba_Dave (Jan 16, 2009)

All 3 older houses that I have resided I have found some ant nests under the siding
Good idea to strip it down to the sheathing
I've also added insulation in a few areas


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## cbzdel (May 11, 2010)

I am looking at doing the same project..

When old siding is removed, is the existing sheathing looks to be acceptable, would there be any reason to remove the old T&G to replace it with something more modern such as OSB or plywood? (I do have blown in wall insulation so I am guessing I dont want to mess with my original sheathing. 

(I already also have all current wiring, everything was re-wired recently)

Thanks!


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## Scuba_Dave (Jan 16, 2009)

Older T&G has more spaces & allows more air infiltration
That said I did not replace it on my house before siding


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## cbzdel (May 11, 2010)

is air infiltration a good thing? seems like it would become problematic and cause more drafts in a house, maybe it helps with any possible moisture problems though??

just trying to think if your comment was pro or anti T&G :laughing:


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## kwikfishron (Mar 11, 2010)

I have no problem with plan assuming your existing siding is in decent shape and the walls are smooth and you’re installing all new trim, flashings, etc.

I’d blow in insulation if you have none.

Post a picture if you can so I can change my mind.


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## Grampa Bud (Apr 6, 2009)

On older homes that were not covered with a vapor barrier inside under the lathe or drywall or covered with a vapor barrier outside under the siding it is best to follow the 1x6 or 8 or 10 or 12 sheathing route after checking out your wall interiors. The sheathing spacing allows the wall to breathe and helps curtail any moisture problem in the older homes. When you go Hi tech with all the newer insulations, 4x8 osb plywood sheathing, Tyvek vapor barriers, etc. you are trying to make your building air-tight to squeeze an extra nickel out of your HVAC budget. The old way or the new way both work well and if your building is older and has ample insulation do like Scuba Dave says. He's spot on.


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## Tom Struble (Dec 29, 2008)

uuuggg,tyvek is no vapor barrier


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## loneframer (Mar 27, 2009)

If it were my house, I'd make sure the siding is solid, nail it off well to the framing to insure a positive connection, paper it with #30 asphalt saturated felt, pack out the window trim, if needed and wrap them with trim coil, incorporating a flashing detail into the wrap. Side away.:thumbsup: Water management is paramount on a siding job and starts at the substrate level, not with the siding, but needs to be incorporated into the siding for proper function. 

Did I miss anything Tom?:huh:


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## Tom Struble (Dec 29, 2008)

show off:no:


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## cbzdel (May 11, 2010)

what does pack out the window trim mean?


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## elsobrider (Aug 3, 2010)

My existing siding is in good condition. I just hate the way it looks and like the classic lap siding look. As long as my spot checks don't reveal mold or rot i was planning on all new trim and flashings. What does pack out the trim mean? 
Thanks for all the replies.
.


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## loneframer (Mar 27, 2009)

elsobrider said:


> My existing siding is in good condition. I just hate the way it looks and like the classic lap siding look. As long as my spot checks don't reveal mold or rot i was planning on all new trim and flashings. What does pack out the trim mean?
> Thanks for all the replies.
> .


 If you're going over the old siding, the windows may not project out far enough to receive your siding cleanly. In which case you will need to do something to thicken, or pack out, the jamb, head and sill areas to bring them out far enough. Depending on what your old windows look like, there are several solutions that come to mind.

If they are older style windows, after they are packed out, they should be wrapped with trim coil and sealed properly to prevent water intrusion.

There are other trim details that can be incorporated into newer style windows to achieve proper thickness as well.


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## Tom Struble (Dec 29, 2008)

what would these ''other trim'' details consist of mr lone?:wink:


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## loneframer (Mar 27, 2009)

tomstruble said:


> what would these ''other trim'' details consist of mr lone?:wink:


Well, you have the rabbeted 5/4, the non rabbeted 3/4 with a 3/4 overlay or the full 5/4 butt, as seen on all the trim details in the last pic, just to pull a few out of thin air.


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## Gary in WA (Mar 11, 2009)

Doesn’t the paper go *over* the head-flashing and field nailing belong in the center of the *slot*.......(ripple alert)? Or do you rely on sticky tape over the doors?


"If a nail slot does not allow centering/securing
into a nailable surface, use a nail hole slot
punch to extend the slot and allow centering of
the fastener." From: http://www.vinylsiding.org/publications/0804_VSI_2007Manual.pdf

Be safe, Gary


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## loneframer (Mar 27, 2009)

GBR in WA said:


> Doesn’t the paper go *over* the head-flashing and field nailing belong in the center of the *slot*.......(ripple alert)? Or do you rely on sticky tape over the doors?
> 
> 
> "If a nail slot does not allow centering/securing
> ...


I slit the paper above the flashing and tuck a "counterflashing" in above the door as I work the siding up. It gets ran several inches past on each end and lapped onto the nail hem of the last full coarse on the side casing. Just a little extra protection. The bottoms of windows get a similar treatment. The flashing is installed with the window, behind the nailing flange.

As for the nailing on the siding, all simulated shake panels have a centering hole to prevent the panels from wandering apart and disengaging the side locks that keep the laps tight. It also looks much nicer when the spacing at the laps stays consistant across a large wall.


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## Gary in WA (Mar 11, 2009)

Nice job on the install! Think like a raindrop...... I'm glad you followed up with pictures and info so DIY'ers learn the correct way. 
The picture with two houses so close together reminded me of the 5 houses that burned quickly here in '09 from someone burning trash in his wastebasket on the back deck. The houses were the required (minimum) 10' apart but with the wind and them having vinyl siding...... Certain things we can control, but concave window glass in a new window? http://www.google.com/url?sa=t&sour...9-3UCw&usg=AFQjCNF_qMwTVEWLXNtl1vk4U3c5XIx76A

Be safe, Gary


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## loneframer (Mar 27, 2009)

GBR in WA said:


> Nice job on the install! Think like a raindrop...... I'm glad you followed up with pictures and info so DIY'ers learn the correct way.
> The picture with two houses so close together reminded me of the 5 houses that burned quickly here in '09 from someone burning trash in his wastebasket on the back deck. The houses were the required (minimum) 10' apart but with the wind and them having vinyl siding...... Certain things we can control, but concave window glass in a new window? http://www.google.com/url?sa=t&sour...9-3UCw&usg=AFQjCNF_qMwTVEWLXNtl1vk4U3c5XIx76A
> 
> Be safe, Gary


 Yep, Low-E glass is causing it's share of issues.

Many of the houses I've built over the years are only 8' apart, but are required to have fire rated sheathing on the outside walls and Type-X wallboard on all bearing walls. I've been around new construction for 25+ years and am still learning and re-learning as new methods, materials and requirements emerge. Her's a pic or two of the 4' setbacks.


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