Expert: Bruce E. Johnson - 4/29/2008

Question
1.Do you recommend pouring footers first or doing a grand pour whereby you pour footers and foundations walls all in one pour. I am building a small barn 22 by 32.

2. When do you set your anchor bolts--before pouring or set them into the concrete?

3. Do you think I would need expansion joint for a structure of this size? (I am thinking about pouring the floor.)

Answer
Hi Sean, 1. I have done individual pours and monolithic pours and I prefer the individual pours because it is easier to form up the walls if you have a nice poured footing to work off.  You can snap lines and brace your forms and nail kickers to a poured footing and you get a little nicer job.  With a monolithic wall/footing pour you have to support your wall forms in mid air and keep them stabilized during and after the concrete is poured until it is set up.  Then you have to remove any supports from the poured concrete that were used to suspend the formwork.

2. I have my anchor bolts laid out and ready to go and generally wet set them in the concrete as I pour.  Tricky column pads that require the bolts to conform to a specific pattern for the setting of structural steel need to have a template made of plywood to mimic the column base bolt pattern and then the template is held in place  by braces or other formwork until the concrete is poured.  If you are just doing bolts for sill plates I would wet set them. If you are pouring the wall by yourself and might not be able to get back to setting the bolts prior to the concrete setting up on you then a simple method of bolt placement is to take a short piece of 1x4 and drill a hole in it.  Stick the bolt through the hole and nut it on top and then  span the 1x4 across the wall form work and tack in place with a #8 duplex nail on each wall form.  Then as you pour you can screed the wall off  and keep on going without having to worry about your concrete setting up on you.   

3. Expansion joints are wise but seldom done in the foundation wall itself.  Most expansion joints occur above the foundation in masonry or poured concrete walls.  We cut our joints in floor slabs with a slab cutting saw as soon as the slab is finished and can be walked on.  These control joints encourage the slab to crack in isolated areas.  Concrete will crack eventually.  By cutting one inch deep cuts you make the concrete crack where you want it to.  A slab your size would probably need a center cut each direction.  When using wire mesh reinforcement in slabs it is considered a good idea to cut every other wire in the mesh where your control joints are located. It is a simple process and again encourages the concrete to crack along those lines.
I hope this information helps, feel free to write again regarding this or other matters, sincerely bruce e johnson