Pier And Beam Foundation Repair Methods

Frequently Asked Questions

1. QUESTION:
   what is the best method to repair a pier and beam foundation on clay soil?
   House was built in 1924 in Central Texas. The cedar peirs were replaced in 1999. The house is just on stacked block right now. Too much movement this winter. All the bids I have received so far are for spread footings or pressed pilings.

   • ANSWER:
     Spread footings would be a good choice usually. You might consider doing some over excavation and re-compaction with engineered fill to prevent the problem in the future. The only problem with this is that it would be very costly on an existing structure.

2. QUESTION:
   Structural engineering question?
   First the background: I want to build a house using CEBs, Compressed Earth Blocks. (If you want to know more about the CEBs check out thes link: http://www.adobemachine.com)

   They are considerably heavier than conventional building materials. Each block is 10″wide x 14″long x 4″ thick. They will be stacked with the 10″ side facing out and thus will make a 14″ thick wall course. The exterior walls will be two courses thick with a small chase between them to allow for electrical and plumbing. The interior walls will be one course.

   Each of the blocks weighs about 40 pounds. Stacked as stated above that will create a wall that weighs 14,400 pounds per 10′ x 10′ section for each course and thus a 28,800 pound 10′ x 10′ section for the double course.

   My main question is: what is the formula to determine the thickness of the of footings and slab given the width of the walls and the weight?

   Once the floor plan is finalized and the interior walls laid out and the lengths of the exterior walls determined I want to be able to estimate what the foundation work and materials are going to run me.

   I would also like to build this with a flat top roof (a little slope for rain runoff of course,) and I would like the roof to be make of concrete. How do I do that? Do you pour it in forms in place or do you precast it in sections and then crane it into place? How thick can/should it be (I want it to be tornado proof?) What sort of support is required during construction and afterwards. The interior walls will provide some support but the rooms will be large and I am wondering if I will have to have support beams from the floor up or will I need support beams spanning from wall to wall at the ceiling (I-beams?)

   Also should I use foundation support piers (like the foundation repair guys drive down to bedrock when they repair a broken or cracked foundation?) I was wondering if that would help support something as heavy as this house is going to be.

   • ANSWER:
     These are all great questions! I really do enjoy designing the structures for all kinds of buildings, especially custom residential homes. This seems like it will be a great project by the way you describe it.

     First of all I want to suggest that you have a licensed structural engineer to work along side you during your design process. The questions you have posed here have fairly complex answers and you may not have thought of all the implications of your design materials yet.

     I would also like to suggest that you employ a geotechnical engineer to investigate the soil on your property. They will be able to determine just what types of loads can be supported and by what types of foundation. They can also help with suggested procedures for preparing the sub grade soil prior to laying a foundation if it needs any type of enhancement or modification to best serve your home’s needs.

     Lastly, I would suggest having an architect review your final design, they are aware of building codes for your area that you may have missed in your initial layout. They might even offer some good suggestions for details on how to waterproof the exterior of your building.

     Anyway, your initial calculation about wall weight is off by a lot, a 10′ x 10′ section of brick should only weigh 4,200 lbs based on your weights and brick sizes. Plus you didn’t account for the weight of your roof, nor for snow, construction, or wind loads. And it seems you are only concerned about the roof being tornado proof… that kind of a design needs to be a whole system approach (walls, foundation, roof, doors, windows, etc.). FEMA puts out some documents to recommend how to create a safe-room, but they don’t make for very pretty homes. I would instead suggest a single safe room made to FEMA standards or better and let the rest of the house blow away. Tornado force winds are too strong for typical construction methods.

     My guess is you would rather not pay the fees for design professionals to come along side and help… but if the building falls down a concrete roof will be devastating. Besides, your local jurisdiction likely requires that you adhere to a building code like the International Building Code. Rather than learn it on your own, along with all the structural design equations, I suggest building a design team to help your dream become a reality.

     Please contact me directly (check my profile for email link) and I’ll help walk you through some of the basics to help get your basic design off the ground before you go to talk to a local professional.

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