# filling cavities with foam?



## beastmaster (Nov 3, 2007)

Yesterday we braced a Modesto ash that had split. Another company that specialized in diagnoses of tree diseases and defects recommended us to do the repair(we used all thread) The tree had several cavities, including one large one in the lower trunk ware the condiment limb(half the tree) had started to split, They had filled the hollow with foam. I thought that filling hollows or cavities with any thing was no longer practice, and that moister trapped in there could do more harm then good. I'm wondering if others ever use foam or what your opinion on this would be.Thanks


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## treeseer (Nov 3, 2007)

ansi says no way does foam add support. i've read where shigo says it can. I don't know enough about how much it traps moisture and how much it lessens twisting to say one way or the other. I've used it a few times but never went back to check.


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## M.D. Vaden (Nov 3, 2007)

Seems this topic came up in the past year or so.

Anyhow, I decided to start using expanding foam to seal cavities, like when bees are known to build hives.

My preference would be summer application when the cavity is dryer.

The plan is to cover the hole with a template, punch a hole for injection, and drape a plastic skirt to catch foam that oozes out so it does not stick to the outside of the tree.

I'll probably be using the black foam that is used for water features / ponds, as if it's safe for fish like the label says, its probably extremely low for toxicity.

One firmed the next day, it slices right off with a machete, saw or blade. 

The foams are also flexible.


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## SilentElk (Nov 4, 2007)

If support is want you want, I hear concrete with a few sticks of rebar are the ticket. Although it doesnt flex worth a darn.


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## Justice (Nov 4, 2007)

I have used foam several times. Not to add structure, but to keep moisture out, and water from ponding in a hollow. Idea is to seal out air and moisture, and thus slow decay. I have been monitoring them for a year now an they appear to be OK. I also put galvanized mesh inside the opening and foam out covering the mesh with an inch or two to keep squirrels out. They go right threw the foam otherwise.


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## highasatree (Nov 4, 2007)

I've Heard if you shape the foam and then apply a layer of bondo (car body filler), you can make the wound look inconspicuous on the tree.


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## Upnorth (Nov 4, 2007)

wouldn't filling with foam also trap moisture in the cavity? as well as reduce air circulation?


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## mckeetree (Nov 4, 2007)

Upnorth said:


> wouldn't filling with foam also trap moisture in the cavity? as well as reduce air circulation?



It does. It is not a good idea.


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## Urbicide (Nov 4, 2007)

*Is there a tree dentist on call here?*

So what would you recommend? I have a number of trees on my woodlot that have hollow cavities that seem to collect all sorts of debris as well as water. My thinking would be to clean out the cavities, dry them out, then fill the cavity with something to keep the stuff out of them.


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## highasatree (Nov 4, 2007)

My thinking is to leave the cavity open so that there is air circulation and to drill a hole so any water in the cavity can drain out .


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## Justice (Nov 4, 2007)

If the cavity is in the side of a tree and you use foam when it is dry, and you apply it correctly it seals itself against the tree. Thus sealing out moisture and air. The right foam is water proof. Otherwise the hollows just keep collecting water. This way the water runs down the side of the tree and over the foam and continues down the tree instead of filling the cavity with water again. 

This is different if the hollow is in a co dominant situation, or where the decay is in a vertical hollow, or if you used a filler that is porous. 

I will know more when I eventually remove the tree's I have already treated.

How big are the cavities your trying to fill? Pictures?


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## Beast12 (Nov 4, 2007)

highasatree said:


> I've Heard if you shape the foam and then apply a layer of bondo (car body filler), you can make the wound look inconspicuous on the tree.



That is what I was taught. Then it kind of gives the tree something to heal over. I was taught this about 8 years ago. Is this no longer a normal practice?

-Matt


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## lxt (Nov 4, 2007)

I dont know about air circulation & all that, seems to me a cavity if left untreated will grow larger( ask your dentist). I fill with foam after making sure the cavity is clean.

I dont use cement & definately not rebar, if you ever have to take that tree down it will be a pain!!

LXT..........


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## Fallen Angel (Nov 4, 2007)

I was taught to use foam and have done it for years. It doesn't stop the decay but slows the process. After the foam has expanded and hardened you can use a technique called bark traceing to permanately seal the wound. As far as support to the heartwood and cambium layers....don't think it will add any, but it is better than nothing at all. PLEASE don't use concrete and rebar...chains are too expensive and it makes for a hell of a time removing the tree in the future.


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## lawmart (Nov 4, 2007)

The last time i brought up this topic i got a little butt slapping, But what the heck. i have been filling cavities with foam for over 12 years now and it is not meant for any type of structural strength.
But as a barrier for insects and little critters from increasing the cavity size.It helps / beneficial if the cavity is dry,and to clean out the cavity first and if you can to spray to kill any insects that are possibly there, and . I use metal screening over the face of the cavity to stop any big critters from re entering the hole. You can spread bondo/ fiber glass over the face and paint it to match the tree colour if you so desire i have clients paint faces on it what ever floats your boat. 
For who ever dis agrees with the practice it does not hurt the tree, from my experience.
if you leave the cavity open there is a grater chance that the walls (codit) will be breached and decay will increase. 

just my 2 cents , but always open for some other info .

Lawmart

Play safe


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## lawmart (Nov 4, 2007)

The last time i brought up this topic i got a little butt slapping, But what the heck. i have been filling cavities with foam for over 12 years now and it is not meant for any type of structural strength.
But as a barrier for insects and little critters from increasing the cavity size.It helps / beneficial if the cavity is dry,and to clean out the cavity first and if you can to spray to kill any insects that are possibly there, and . I use metal screening over the face of the cavity to stop any big critters from re entering the hole. You can spread bondo/ fiber glass over the face and paint it to match the tree colour if you so desire i have clients paint faces on it what ever floats your boat. 
For who ever dis agrees with the practice it does not hurt the tree, from my experience.
if you leave the cavity open there is a grater chance that the walls (codit) will be breached and decay will increase. 

just my 2 cents , but always open for some other info .

Lawmart

Play safe


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## lawmart (Nov 4, 2007)

woops id it twice.


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