Rubble work for Foundation of House construction

At Cochin Foundation work for house construction is generally costly as most of the land in Cochin are marshy land sometimes without even a trace of sand to depths as high as 12 to 15 metres.At Elamakkara where I have built a house of about 3000 sft in 2004 and presently building a house of about 3600 sft,I had to do concrete piling for foundation to depth of about 14.5 M.Similarly at Vyttila,Kathrikkdavu,Karukappilly,I had to do concrete piling.With after piling works like raising pile columns,Foundation beams,basement brick work,filling plinth etc,Foundation costs in these cases have gone up to about Rs.10 lakhs

At Kaloor,Edappally,Palarivattom,Kalamassery,Kakkanad I could do with less costly rubble foundation as the soil in these places were stable with either abundant sand or laterite.

Rubble foundation traditionally was done in most of the places as rubble masonry using rubble joined with sand cement mix or mortar with low mix ratio mostly as low as 1:10.Mortar when compared to rubble has low strength even after curing with water whereas the strength or bonding is better when used with brick normally with a mix ratio of 1:8.

My Guru Architect Angelique has taught me to use rubble work in dry pack for foundation as well as for basement.She was trained extensively under renowned Architect Lawrie Baker and thus i inherited all those cost reduction methods on building construction.

As usual I never accept anything unless I am fully convinced about correctness of the method adopted.Procedure followed by her were duly followed by me with no change(As I am fully convinced about it)for Foundation work adopted by me using rubble is detailed below:

In a stable soil we do not dig a lot unnecessarily.In southern Kerala there is a widely accepted belief among people that whatever may be the strength of soil,one should dig at least 6 feet down for foundation rubble work for house.After digging 6 feet,mostly very stable soil(sometimes even laterite soil)they put p c c 1:10 in the bottom.Then the rubble worker will simply throw rubble pieces into the six feet excavated foundation area.By such throwing of rubble,p c c will get damaged fully.nobody bothers.Once rubble filling reaches ground level they will build rubble basement above without doing anything extra for foundation rubble work in cement mortar of mix of 1:8 usually with cement plastering on top.If any builder or Engineer deviates from this generally accepted procedure not only the house owner but the entire people of the area will come and start abusing the person showing courage to deviate from the accepted practice.

I have faced this music and felt the heat very well when I built house at Ranni.Neither the owner nor the local people were willing to accept our procedure of rubble work for foundation.Let us see what we do instead.

We do not dig more than 45 cm (1 1/2 feet) depth if the soil is stable.If the soil is hard laterite we do not even go down excavating more than 15 to 20 cm.We do not put p c c in stable soil to be broken by throwing of rubble pieces by rubble mason while doing foundation work.We tell our rubble worker to closely pack rubble in dry pack method for foundation up to a height of 60 cm thereby keeping about 15 cm foundation rubble work above ground level.After this dry pack rubble foundation work,we force fill gaps of rubble work first by putting crusher sand above foundation work and then forcefully pumping water inside.As the crusher sand gets filled up inside dry packed rubble foundation,a stage will reach when no water will go down as it is fully packed with rubble and crusher sand making almost monolithic rubble foundation quite strong base for your house.

After this we build basement again by dry pack rubble work but with a slight inclination sloping basement from 60 cm to 45 cm to a height of 45 cm for basement to add strength.We point outside of basement rubble work with mortar and plaster top of basement with a rich mix of mortar of 1:6.Inside of this rubble basement is open to receive forced filling of filling material usually red sand of powdery nature

At Ranni I had to threaten to leave the work to make my client to agree to follow this procedure for Foundation rubble work and I have also given personal guarantee for the strength of work.Till completion of the work client and people around the area had doubts about our Foundation work.Once convinced Father of my client used to talk about others following usual procedure as fools and I used to enjoy his comments to that effect.

At Thiruvalla I was asked to leave the work due to my unwillingness to follow their time tested or traditional method of foundation rubble work and I left the work in between rubble work.

At Chengannur,client reluctantly accepted my method of foundation rubble work.

At Cherthala and at many other places local people used to call me mad for doing this sort of foundation work and predicted that our Foundation will sink or break open.Once work progressed and nothing bad happened everybody seem to forget about their predictions.

At Kalamassery,another contractor was building his own house near my site .My client was an Engineer.Our neighbour contractor was very much critical about our foundation rubble work"without even a bag of cement".He told my client and his wife about how bad our construction is.He assured my client that our building will sink or crack or foundation will get damaged thereby causing damage to house.
My client in spite of my assurances was jittery.

Neibour contractor has done a retaining wall in cement mortar without proper packing for his boundary wall. As I predicted retaining wall done by him has fallen apart one day and then he silently did it again as dry pack rubble work with better packing of rubble.Therafter he stopped criticising my work and started asking my client about my plans for balance work of the building.Only after that falling apart of bounday wall of neighbour,my client really started believing my words.