Wood Dry Rot Repair Specifications

[smwa]

Hi All,
I'm involved with a multi-unit housing retrofit project which includes dry rot repair for many of the architectural elements. I'm wondering if there are general specifications for dry rot repair that I can use as a starting point. I looked into Masterspec index and didn't see anything for dry rot repair.

Thanks,

 

[msquared48]

It's called remove and replace.

Additionally, the resason for the rot has to be determined and corrected during the "repair".

Question:

Why, as a Structural, are you concerned with Architectural elements? Why not let the Architect deal with it?

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[smwa]

Hi Mike,
Thanks for the response. I was trying to see if there are specifications for treatment when the damage is only minor. And if there are standard specifications to allow contractors to determine "replace" vs. "treatment" options. I agree that "remove & replace" is probably the safest way to go.

In my project, there are many cantilever balconies that have varying degrees of dry rot, and the "remove & replace" method can be quite invasive to the interior space. In this case, the balcony is not just an architectural element and the architect is being diligent on asking for my input.
In your experience, is "remove & replace" the only way to approach dry rot repair?

Thanks,
Stan

 

[msquared48]

That's what I use, primarily.

Paramount though is to find out what caused the condition in the first place and correct that so it does not happen again.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[MiketheEngineer]

Agree w/ M^2. But dry rot is a misnomer. Nothing ever rots if it is dry. The wet rot just dries out.

Cantileverd balconies were the rage about 15-30 years ago. A real bitch to repair. I usually suggest a knee brace type replacement or additon of posts. Much cheaper and widely accepted.

Install new deck with ledger and posts or knee braces. OR tear out the ceiling???

 

[Ron]

Mike is exactly right....plus, the damage is rarely "minor". If you have wood rot (dry rot is not a proper term...it was wet in the past, but might be "dry" now).

I assume you are dealing with this as a forensic venture or in response to a client request. YOU MUST determine the cause. Remediation is futile without correcting the cause of the damage.

Give us a little more info, such as...

Is this a stucco project?
Where is the damage located and how was it discovered?
Which architectural elements are involved?
Do you know if the structure has been affected? Most often the answer is "yes".
Have YOU done an adequate investigation? If not, you open yourself to tremendous liability.

I've done lots of these...give us some info.

 

[Brad805]

It can depend how significant the decay is. If you can easily pick at the boards and it flakes off, its gotta go. If not, you may be able to pin point the decayed regions using stress wave testing or another non-destructive method. Once you know the extent of decay you may be able to add new joists, beams, or stiffen the existing somehow and reduce the amount of architectural damage that cost so much. The downside of the testing route, is each piece can be different and it can take a lot of time to figure it out and put on a drawing. Unless your client is willing to pay for your time, remove and replace is the safest method.

The architectural damage is usually not the only costly part. If you have any electrical or mechanical constraints, this repair work can become a major expense for the owner.

Boron rods can help reduce future decay, but they will not work in all cases and there effectiveness will reduce over time.

Brad

 

[Ron]

Boron is only effective against insect infestation...it doesn't help for water intrusion, and is less effective as a termiticide/insect repellant under moist conditions.

 

[smwa]

Thanks for all of your input, and here are some more info on the project:

The project is a 50 unit low-income housing complex consisting of four separate two-story wood frame apartment buildings. The areas of visible wood rot is at the cantilever balconies, exterior wood stairs & rails, and window sill & trim.

The balconies have bad draining and failing waterproofing membrane that will be replace and detailed by the architect.
The exterior wood stairs just have not been maintained, and the wood posts were not raised off the ground. The window sill & trim will also be address by the architect.

The developer for the renovation wants to repair all of the wood rot and is expecting to find additional wood rot once the building is opened up. The intention is to repair the waterproofing issues along with the framing repair.

Thanks,
Stan

 

[msquared48]

Were the decks vented at the soffets?

If not, they need to be, or the same condition will occur again if the decks leak again.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[Brad805]

Ron, I believe some Boron rods are effective to a degree for decay prevention. We had a PHd research prof working with us on school projects years ago, and this was one preventative measure added for a number of cantilevered glulam beams. Maybe I am missing something.

Brad

DESCRIPTION The Impel®Rod is a highly concentrated solid formed, water-diffusible borate rod
created from compounds of boron, a naturally occurring preservative element. The rod combines with water to become boric acid, which has long been recognized as a natural inhibitor of decay-causing fungi and insect infestation. Once the Impel rod is inserted into damaged log ends, it remains inactive until moisture in the wood increases at which time it slowly dissolves and the moisture stream carries this fungicide along the wood fiber paths to saturate the rotting areas. When the wood dries and moisture levels drop below approximately 25%, the preservative becomes dormant and provides a reserve that is ready to reactivate should decay-conducive conditions reoccur.

 

[Ron]

Brad..thanks for the info. Interesting. Most of the rot we deal with is for conventional wood or OSB. Insertion of rods is too localized and the sprinkling of powdered boron/borate products has not been effective. Will give it a look, though.

 

[csd72]

As far as I am aware, the only truly effective treatment for dry rot is to remove and replace as well as resolve the cause.

The extent of the roemove and replace varies from removing localised sections and replacing them with epoxy to the complete replacement of the member.

If you completely remove the rotten sections and remove the source of the water ingress then I cannot see what you would need the boron rods for.

By the way, over here dry rot is a legitimate term and it refers to rot that occurs at a much lower moisture content than wet rot.

http://www.kenwoodplc.co.uk//index.php?main_page=page&id=14

 

[Brad805]

csd, I have always found timber decay terms are not used correctly very often. If a piece is truly fully decayed, then I agree, boron rods are not of any use and replacement is the correct solution. I also agree that these rods are not intended for joists or other thing materials. If there is only minor damage, we engineers can spend huge sums of time figuring out options and still save our clients a large sum of cash. Renos tend to be nothing but problems once you get into them.

In the case where we added the rods, we had exterior glulam beams that were covered by a roof. After completing stress wave testing and mapping the extent of decay, we back cut the beam ends, and added the rods as a preventative measure. Covering the beam ends was not an option. If I recall correctly, the boron does cover a larger area than just the rod.

In the OP's case I didn't follow his exact beam/joist arrangement nor did I notice if any of the elements were exposed like so many archs like to do.

Brad

 

[msquared48]

VENTING!!
VENTING!!!!!!!!!
VENTING!!!!!!!!!!!!!!!

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask