We have created this Foundation Help & Advice centre to answer your questions about GreenRaft and its insulated foundation solutions. We are also providing information on various foundation types to explain the reason why a particular foundation might be used or has been selected by your structural engineer.
It is not an exhaustive list, so if you have a question that needs an answer, please let us know. Hopefully, we will add your question to the section.
There will be some linking between the topics where subjects overlap, This should give a better understanding of the various foundations and how they are used.
It is a huge topic, so you will also find links to other authoritative sites where more in-depth articles are available.
The main factors that influence what type of foundation might be used are the load of the structure, the bearing capacity of the soil, the width of the foundation upon that soil and other site conditions. These site conditions may be soil and strata mixtures, water tables, nearby trees or removed trees.
Help Centre Main Topics
Across the top are five topics related to foundations, that make up this Foundation Help & Advice Centre. The topics cover foundation types, foundation design, thermal performance, costings, and installation.
Pick which one seems most appropriate for your question and see if the answer is in there.
What are Strip Foundations?
Strip foundations used to be very common in are the most common type of foundation used in UK housebuilding today. They are popular because they are relatively cheap and can be formed simply without too much fuss.
The “strip” footing falls into the category of “shallow foundations”. It s similar to a “trench foundation“. These two terms, “trench” and “strip” are sometimes used to describe either type. The main difference is that strip foundations are not usually as thick as a trench but may be wider, and its strength comes not so much from the mass of concrete but more so from the reinforcement cage that gives the strip its strength and rigidity. A strip foundation contains much less concrete.
A Strip footing is more labour intensive and it needs shuttering to form the shape of the footing.
How To Build A Strip Foundation
A strip footing requires considerably more skill than a trench footing in its preparation. A formwork must be made to shape the concrete to the engineers design. The formwork is usually waxed or oiled to stop the concrete from binding to the temporary formwork Reinforcing steel needs to be added as per the engineers design.
Reinforcing steel is usually made in “cages” and inserted into the formwork to a specified depth ,.
Building Control will usually inspect the ground below and the steel tying, before the concrete can be placed. they
The top of the concrete is made as level as reasonably possible. The top of the concrete is usually just below ground level. Once the concrete has cured sufficiently a short rising wall (sometimes called a stem wall or dwarf wall) is built from the top of the strip footing to above ground level. This wall can be brick, block, trench block or can be reinforced concrete. A suspended beam and block floor can sit on top of this wall if a cavity is required under the floor. Alternatively a ground bearing concrete slab can be poured to create the floor at ground level.
Pros & Cons of Strip Foundations
- Pros – Can use less materials than a trench foundation
- Cons – Labour intensive and requires greater skill set than a trench
- May require more dig of the top soil across the site to allow proper access.
- Difficult to make thermally efficient