In our latest blog, we take a step back – right to the beginning of the project to build a new, straw-bale Hastings Country Park visitor centre – now called The Bale House. In this post we’ll explain and explore how the groundworks and foundations took shape for this exciting new building.
The new Visitor Centre is located next to the old one in the Hastings Country Park. The park itself is an Area of Outstanding Natural Beauty (AONB) and a Site of Special Scientific Interest (SSSI) and its position is perfect to take in the glorious views across this beautiful landscape. Although the site might be considered a challenging choice for some, in that it’s near a cliff edge with horizontal wind and rain likely at times, the design of the Visitor Centre eliminates any concerns of the possible ‘wetness’ of the site, principally through the use of timber rain screen cladding on the side of the prevailing wind (the south and west).
Groundworks, simply put, involves excavating material from the building site to the point where the foundations of the building and surrounding area can begin. Once Huff and Puff Construction had cleared the site and completed the groundworks our attention turned to building its foundations.
Focus on Foundations:
The site of the Visitor Centre is a mix of heavy clay and sand through to mudstone and sandstone. Areas of the site under the building had to be excavated to different depths to find good bearing ground. Deeper areas were filled and compacted with recycled crushed materials and compacted to create a level surface. A limecrete (the lime version of cement-based concrete, using hydraulic lime, sand and aggregate) base was then poured. Ashlite concrete blocks were then used to create plinth walls (low walls for the rest of the structure to sit on). These blocks are made from 100% recycled concrete and these blocks took us up to ground level.
On top of this, two courses of ebony bricks, were laid using NHL 3.5 hydraulic lime mortar, which took us 200mm above ground. (NHL 3.5 lime is slightly softer and accommodates movement).
Huff & Puff Top Tip: The mortar should always be softer than the bricks – because then any movement cracks the mortar and not the bricks (which would cause structural failure). Although we would try to eliminate movement by design (with good foundations) straw bale buildings can naturally accommodate a very large amount of movement – unlike masonry where movement could cause serious structural damage.
Floor buildup:
The most common solid floor construction, in standard non-straw building projects, uses a plastic damp proof membrane, a lot of petrochemical foam (for insulation) and cement-based concrete. Instead Huff and Puff Straw bale Construction methods ensure the use of a product called foamed glass gravel (made from recycled glass from bottle banks) for the main floor substrate. This is insulating and hydrophobic, so it creates an insulated floor that will not absorb moisture (it creates a capillary break) – all without using petrochemical products. On top of this is a 100mm limecrete screed. This creates a completely breathable (vapour permeable) floor, just like our walls.
There have been some challenges encountered during the foundation stage of the build, and we did encounter a seam of fine silica sand on the site. This was interesting because historically, very close to the site, there was a quarry that extracted this sand. For those interested in the history of this site, it was the Fairlight Mining Company back in May 1939, who leased land from a Major Sayer between the top of the Warren Glen and Fairlight Church to dig for this silica sand (used for making optical lenses etc.). It created the large quarry at the top of the glen and a smaller one nearer the church, which today is the site of the Hastings Country Park car park. Overall, the sand itself was less of a concern than the amount of clay that we also encountered at the site. Clay is prone to movement through a freeze/thaw action. So, most of our excavation work, therefore, aimed to remove the clay down to mudstone or sandstone, which is much more stable.
Huff and Puff Construction would like to thank all those who worked so hard on the foundation stage of this build, including the team at Red Kite Design and Build.
In the next blog we’ll take a look at the next stage of The Visitor Centre’s build – as we focus on the timber frame and roofing aspects of this exciting project.
