On the right footing… foundation types for garden rooms
Have you been wondering about which type of foundation system might be right for you and your garden room? If so, you’re not alone; we’re asked on a daily basis about the wide array of options discussed with groundworks experts and we have several of the preferred types to highlight for you as a reference:
Solid Concrete Slab This is the preferred option for most Garden Room Suppliers and Groundworks Professionals alike, it’s quick to prepare, it’s the most solid foundation system available and is wonderful for the Garden room installers but the one downside is that this system is not very environmentally friendly. Concrete slab foundation systems are normally formed to the same external diameter of the garden room and a minimum of 100mm thick. A client of ours has just had her slab installed in advance of her Rotunda arriving and an example of it is shown below:
Average cost for a 4.5m diameter Garden Room £1,500 – £1,950 —————————————————————————————————————————————————–
Swift Plinth and Eco-Base Foundation System
This is a neat little system which supports the Rotunda on a dozen or so ‘feet’ which are small recycled concrete ‘pyramids’ sitting on top of plastic eco-grids which are 1m x 1m in size (which are set about 10cm down in the soil and packed with hardcore or gravel) at load-bearing intervals around the perimeter to support a timber sub-frame.
I think of this eco-grid system as the equivalent to the Eskimo tennis racket shoe used to avoid sinking down into snow! This means, less concrete, less digging, less time and more flexibility (ie: each footing has an adjustable bracket). The company which provides these also create the plastic grid system which you may have seen used as temporary car-parks in fields and rural areas. The footings themselves are a little expensive though and this system does require a timber sub-frame which would elevate your building up by another 20cm or so. This isn’t the cheapest option, but is probably the most time and energy efficient.
(Average cost for a 4.5m diameter Garden Room £1000 – £2500) —————————————————————————————————————————————————–
- Foundation Block Foundation System The most commonly used system we’ve encountered to date and it comes in at a lower cost than the above options but is more labour intensive and involves a lot of digging. Essentially, holes are dug-out to a depth of between 80cm and 1 metre at regular intervals (spaced out every 40cm to support floor joists) and then foundation blocks built up with cement and hardcore to provide solid ‘pillars’ which support the building. The blocks must protrude at least 10cm from the surface area of the ground to provide air-flow underneath the building.
(Average cost for a 4.5m diameter Garden Room £800 – £1400)
All of the foundation systems mentioned above should also utilise full membrane systems both above and below the footings, to protect the timber elements of the building resting on it and to prevent growth of vegetation coming up from below.
Of course, each and every foundation system available is hugely dependent on the site location, the soil type and gradient of the land. It’d be best to check with a local groundworks contractor before deciding on installing any type of building on you property and obtaining several quotes to ensure you get the best deal. If you’re ever in doubt, feel free to call us at Rotunda (0161) 222 3350 and one of our joiners will be able to assist over the phone or pop over and give you some advice as part of our non-obligation site-survey service!
Have a great weekend everyone!
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