Day 83
July 13th, 2012

This post will cover on 2 topics - 1) Plinth beam casting and 2) Retrospective of Foundation

Plinth Beam Casting
Plinth beam is the horizontal cement beam across the house perphery laid on top of foundation.

This picture shows how the finished plinth beam looks.            

Purpose of the plinth beam is to:

1. Prevent leaking of water into foundation - To prevent a house from settling it is critical that no water be leaked into foundation. Being made of cement, plinth beam is impervious and therefore prevents water from rain, flooding, etc. from leaking into foundation. 
2. Provides support for walls - For load bearing houses, walls carry the weight of the house. Plinth beam provides solid footing to raise those walls.
3. Holds house together - Since plinth beam sits across the periphery of the house, it provides binding force across rooms. For example, without plinth beam it is possible for one of the rooms to settle thus creating uneven floor level. Plinth beam prevents that from happening. 

Basic process to construct plinth beam is as follows: 

1. Mark-up width - Usually width of plinth is half that of the foundation. In this case, foundation is about 18" wide and so plinth is 9" aligning with the outer edge of the foundation. Inner 9" of foundation meshes into the floor level of the house. 
2. Lay down the steel beam - As the adjacent picture shows beams are the core of the plinth beam.  Beams have a loop every 6" that holds it together. 
3. Setup re-inforcement - Before concrete is poured, re-inforcement has to be established to provide rectangular shape to the beam. This takes majority of effort as planks have to be nailed properly in place and once concrete is poured they need to be removed. 
4. Pour the concrete - Next step is to pour the concrete. As concrete is poured, mason ensures that it is evenly spread and smoothens out any edges. He also needs to ensure the height of the beam is consistent throughout the periphery. 
5. Remove re-inforcement - Concrete turns solid within 24-hour and final step is to remove the planks leaving the beam intact. 

This short video explains this process in action. 

Foundation Redone:

To give background context, ground level at living room area is 1' higher than that at the guest bedroom level. Typical height of plinth level is 2.5' that includes 1' of plinth beam and 1.5' of foundation masonry. Turns out though that foundation masonry was 2.5' at living room and 3.5' at guest bedroom. What this meant was plinth height would be 3.5' from natural ground level. This was realized only when plinth beam casting was about to start. To add to misery, by then Rainwater tank was already done to align with 3.5' of plinth !

My architect was clear that plinth level can be no taller than 2.5' or else house would look place oddly high. What followed was no fun - We ended-up undoing a few days of work. Specifically

• Reduce Rainwater tank height by 1' by chipping away at just-finished concrete tank
• Remove 1-layer of foundation stone masonry from across the house periphery to reduce the foundation height by 1'. 

Here is the clip of work being undone. It could have been worse had plinth beam been built. Good news was we caught it at a time that cost us about a week and some cost in material and labor. Having said that, there were key lessons learnt -

1. Trust your gut instinct - Even though as homeowners we may not be in construction business, you have a feel for what's going on. I certainly did feel that foundation was looking tall. While "plinth" was a new term and I didn't know that it was 1' in height I concluded I knew no better. That was the critical mistake. No question is a dumb question especially when you are new to the domain. Had I had surfaced my instinct more strongly or did some research things could have been different. 
2. Working drawing consultation - I independently found my architect and contractor. So they had no prior relationship between them. When architect released drawings there was no consultation that occurred between the two. So, architect didn't get a chance to explain the nitty-gritty and contractor felt drawings were clear-enough. A big no-no ! It is critical that drawings are released to contractor only after architect has had a chance to explain them to the contractor. It is best to have such meetings at the site to relate paper drawings to the actual mapping onsite. Often times, what looks right on paper doesn't feel right to the eye. If that's not possible, have them meet at architect's office. 
3. Inspection schedule - Identify stages at which architect would come and inspect the site to validate it is built according to the specifications. In this case, architect mentioned a couple of times need to schedule inspection. However, given that this was first or second inspection we were not as diligent as needed. 

Again, in retrospect, it was not a terrible setback.. Like many other things in life, none of the lessons were new; rather they were re-inforcement of what you would learn at many other times. Lessons learnt were critical and have since been put in practice. There is now tighter collaboration between me or my wife, architect and the contractor and crisper conversation about respective point of view. So, in the end it definitely had a silver lining !