Cardboard forms

Around here most of the builders are using cardboard for there pier forms under the house and leaving the cardboard in place (in contact with the soil). I have heard that there is a growing concern in regards to WDO’s with the break down of the cardboard etc. I was wondering what you guys think? should we be recommending that the builders remove the cardboard from the pier footings on these new homes?


yes, for that reason and also to view the quality of the pier.

Hi Michael,

This issue is addressed in the IRC as follows:

Leaving the cardboard in situe is clearly wrong and will attract both moisture and WDO/WDI problems. Termites favorite food is celulose.



Cardboard forms left on footings is a “conducive condition” according to the WSDA. In my experience, I have found that this does provide access to Anobiidae, among other things. They should be removed!

I am trying to get my head around this one. Excavate a hole below frost line, insert the concrete form, which by the way is not cardboard but fibre board, backfill to reinforce the form and hold it plumb, fill the form and wait for the concrete to set up properly, usually 2 to 3 weeks, and then you want me dig up the pier and disturb the ground around it just to get the form off the concrete. I don’t think this is a very good idea. Your seem to be defeating the purpose of the pier in the first place which is to provide a secure base to build on. The requirement to build on undisturbed soil would be compromised, would it not?


I doubt that complete removal of the form was being recommended here just removal of the above grad portion of the form if it is a cellulose/wood based product.:slight_smile:

In colorado, cardboard void forms are used where there’s expansive soil. The void forms are just heavy-duty cardboard boxes about 6 inches thick, available in different widths and lengths, designed to support the weight of concrete but crush if the soil heaves.
They’re called “void forms” because they create a void into which soil can move as it heaves.

I see it under foundation walls where the walls float between piers going down to bedrock and under patios and driveways. It’s designed to stay. It’s very common.