Watson Woods Partnership

Watson Woods Partnership

Party Wall Surveyors

Grillage Foundations

This is what a Grillage Foundation looks like. These used to be used to support the columns of steel framed buildings. These days we would use piles. Interestingly this looks like an assemblage of beams and rods and these are certainly intended to distribute load.

costs under Section 11(10)

​Section 11(10)of the Act states that where consent has been given for special foundations on land of an Adjoining Owner and the Adjoining Owner erects any building or structure and its cost is found to be increased by reason of the existence of the said foundations then the  owner of the building to which the said foundations belong shall  repay to the Adjoining Owner so much of the cost as is due to the existence of the said foundations. This clause has often been used to claim cost for removing concrete 'over-spill'. This is wrong.  Over-spill can always be recovered as a loss under the terms of Section 7(4) of the Act. The provisions of Section 11(10) were  intended to address the very significant  implications of grillage type foundations located on a neighbours land.   

Special Foundations

 Special Foundations


This is required to prevent Grillage Foundations being located on a neighbour's land without agreement by using the rights given by Section 1 (6)to place foundations on a neighbour's land.


Section 20  of the Party Wall Act defines 'Special Foundations' as :

"foundations in which an assemblage of beams or rods is employed for the purpose of distributing any load"

Section 7(4) States that "Special Foundations" may  not be placed on a neighbour's land without  the neighbour;s consent in writing.


Recently surveyors have assumed that  Reinforced Concrete underpinning is a "Special Foundation". This has created a situation where neighbours can prevent the underpinning of a Party Wall with no justified reason or can 'lever'  payment or other benefit from a neighbour as the price of giving consent.

WHAT were the authors of the act thinking about ?

David Bowden FRICS has researched and obtained meeting notes  of the  committee responsible for the 1939 Act (predecessor to the current Act). This document clearly show that the  type of foundations envisaged were Grillage Foundations which are an assemblage of beams or rods is employed for the purpose of distributing loadDavid Bowden has summerised his findings in a paper.

For some time Party Wall Surveyors have (In our opinion, wrongly) assumed that Reinforced Concrete (RC) foundations and underpinning structures are 'Special Foundations' which  require a neighbour's consent if they are to be located on the neighbour's side of a boundary.  


Reinforced Concrete is not an "assemblage of beams or rods". It is interesting that the definition in Section 20of the Act does not even mention concrete. That  is because the type of 'special' foundation envisaged by the Act is a steel Grillage Foundation. The concrete encasement to a grillage foundation is just to protect the steel from corrosion, It has no structural role. Whereas, without concrete the residual reinforcement bars in a RC walls have no structural effect, they are an ingredient of the concrete to improve its ability to resist tensile loads and do  not act independently as a structural element to "distribute load". 

Watson Woods Partnership
The Courtyard, 286 Upper Richmond RoadLondon, LondonSW15 6THGB
Phone: 020 8788 7128 Website: www.partywall.info