The most sustainable option would be to return to the way the Victorians built foundations, which was to build walls up off the ground itself, but this is now felt to be inadequate for modern construction methods. Despite decades of experience and millions of homes having been built with concrete, foundation failures remain a significant problem.
find out locally what depth you may have to go to satisfy local building inspector, also check for services that may be burried in the area ,if more than 3 ft deep then get it dug by machine by someone who knows what they are doing. it could be done in a day if not too large and concrete in the next.
Building inspectors work for district councils (ask the switchboard for Building Control) and their workload is normally divided up into wards or parishes so there is likely to be a particular inspector for your patch.
On a standard foundation job, you excavate the foundation trenches to a depth of about a metre. The actual depth is something the building inspector will rule on but if there are no unforeseen problems, a metre is generally accepted as a good depth.
You can’t afford to be complacent about the setting out of foundations – getting it wrong is all too easy. If you end up having to have extra trenches filled with concrete, this means extra cost for you right from the outset.
These foundations are the province of the specialist. You must either hire an independent structural engineer or go directly to a piling contractor.
Please make sure you use all equipment appropriately and safely when following the advice in these D.I.Y. videos. You need to be familiar with how to use equipment safely and follow the instructions which came with the equipment. If you are unsure, you may feel it is safest to consult an expert, such as the manufacturer or an expert Bunnings team member.
A Guide to Foundations of a House/Home Extension All You Need To Know About the Foundations of an Extension…
If its hard to get at all or even part of your foundations, you can make things a lot easier by hiring a concrete pump. This is basically an enormous hosepipe that comes on its own dedicated lorry. The readymix truck empties its contents in one end of the hosepipe and the pump operator can move the other end of the hosepipe around your foundations, thus doing away with the procession of wheelbarrows that usually accompanies a concrete delivery.
The professional you need for this work is a structural engineer and in hiring such a person, you are effectively placing the risk for the success of your foundations onto them, or more particularly, their insurance policy. Consequently, engineers tend to be ultra conservative in their assessments and recommend engineered solutions, such as rafts or, more likely, piling.
There are two approaches to this risk. One is the cautious one, that involves making as many investigations as possible beforehand often this involves considerable expense in itself. Cautious builders dig trial holes and have them inspected by structural engineers who write reports recommending certain courses of action.
As the name suggests, a concrete raft is designed to ‘float’ on the ground beneath. The structure is made up of an extra-thick floor slab, strengthened by masses on steel reinforcing. Rafts have the advantage of providing the base of a ground floor solution, not just wall trenching, but they are reckoned to be rather more complex to construct.
The first step is to lay the foundation of your house. In order to do a proper job, you need to construct two batter boards for each outside corner of the foundation. In order to build batter boards you need either 1×4 or 2×4 lumber, several nails and a hammer. Remember that the batter boards have to be rigid, otherwise while digging the foundation you might move them from the right position. In addition, you have to fasten squarely a crosspiece over the two stakes.
Foundations need to be dug according to a predetermined plan, and to have been accurately surveyed and set out. It is surprising just how often this is not done, and occasionally the ramifications can be very serious indeed, as completed houses turn out to be in the wrong place and subsequently have to be demolished.
Generally, it is better to err on the side of caution and to use as much concrete as is felt necessary to prevent any subsequent problems.
You can obtain a copy of the Party Wall Act for free at legislation.gov.uk.
Follow-on trades are able to commence work immediately on a clean surface, significantly improving build time. It is also flexible in that any shape can be constructed, and allows you to work closer to trees than with other systems.
If there concrete stamps on the site of your foundation, you will have to break them with a jackhammer. This is the easiest and most efficient method to break concrete, but you can also use a sledge-hammer. It will do the same thing, but you have to put more effort and it is time consuming, that is why we kindly recommend you to rent a jack hammer for a day or so.
Water in the bottom of the trench is another perennial problem. Usually you can get rid of most of it using a mechanical pump but sometimes a building inspector will ask for the trench bottom to be flattened off again because, when wet, they can get very chewed up.
You are then faced with a choice of how you fill this metre deep trench. There are basically two methods, often referred to as traditional footings and trenchfill.
Hi. Talk to your council inspector about day joints in the concrete. This is where you concrete in sections that you have dug out . When you pour the concrete you insert rebar into the wet concrete stop end leaving you with a structural joint for your next pour . This will remove the problems associated with leaving open trenches. But you must consult you inspector prior to this as it will depend on your ground condiions
Any advice a building inspector can give over the phone cannot be binding. Should your excavations reveal something unexpected, the building inspector can insist on whatever they think is required to provide adequate foundations, even if this runs counter to what they have indicated to you already.
Whichever method you use, one thing to note is that the level you lay your concrete to should relate to your DPC (damp proof course) level in whole brick or block courses. If you get it right (and you get the foundations level to boot) it saves an enormous amount of work cutting bricks and blocks.
Even if you cut down the trees before you start work, you may still have to make provision for them in your foundation design – the roots continue to live for years afterwards and the impact on the ground by felling a tree can be far more dramatic than leaving it.
If you are building on a steeply sloping site, it may make sense to fit a semi-submerged basement into the sloping ground. Basements are normally an expensive way of gaining extra space but sometimes they can be an excellent solution for a sloping site.
[…] Next month: David begins excavating and pouring the concrete foundations […]
How to dig foundations
hi,firstly befor doing any excavations,always check for any gas,water or electric and sewer pipes.if you go through one of these,s it could cost you a lot of money.so prepare your self properly.get organished.with the side you can ply wood,the secret is not to stand near any trench that you have dug.keep well away.with any trench you will always get a bit of soil come in.so befor you pore concrete go around and take out any spoil in the trench.all the best nick
Angular hardcore needs binding with a thin layer of sand to protect the polythene damp-proof membrane from puncturing and also to create a level bed for the insulation to sit on.
What your building inspector or warranty provider is looking for is principally a good bearing on solid ground. However, you can never be certain just what lies beneath the ground until it’s opened up. This has led to professionals becoming more and more cautious about foundations and specifying loads more concrete or, increasingly, engineered or piled foundations.
You and your builder are the only people who will check the setting out at the start, so take the time to get it spot on. With pegs driven into the corners and chalk lines sprayed on the ground between them, you can start digging the foundation trenches. Mark the centre line of the foundations to avoid confusion; the wall positions will be set out with pegs and string lines later when the foundations have been concreted.
However, there comes a depth (around 2.5m deep) beyond which it becomes impractical and dangerous to work, and the amount of concrete needed to fill the space becomes prohibitively expensive. If the site requires deep foundations in more than a couple of spots, then it is now usual to use a different approach, most often piling, occasionally using concrete rafts.
We have tradesmen ready to help you. Post a job, read reviews and hire today.
RMC have introduced a self-placing foundation concrete called Foundation Flow. It saves on having to barrow, dump or pump concrete around your foundation trenches as it finds its own level around your trenches with a minimum of assistance. It sells for 10% premium but they reckon you can claw back the costs through labour and/or plant savings.
You'll need to set aside a day to comfortably complete this project
You can transport the soil from the foundation, by using a wheelbarrow. The wheelbarrow is a great tool, as it allows to to deposit the soil near the construction site, without putting too much effort.
Today, many people recommend that you undertake a professional ground survey before you start work. Trial holes are dug around the site so that a view can be taken on the best means of placing the foundations.
Your plans should identify all the load-bearing walls and the width of the trenches to be excavated. The depth of excavation is harder to predetermine and this is routinely decided by the building inspector on site. This is where things can get a little bit tricky, because if you have a difficult site, the foundation trenches may have to go down two metres, sometimes even more, below ground, which is expensive and potentially dangerous.
[…] you excavate your foundations, save the spoil to create features in your garden. Ask your groundworkers to put any clean topsoil […]
Hi I am about to construct a single storey wooden framed office in my garden. The dinensions will be 7 metres by 12 metres and a height to the top of the pitch of 4.2 metres. I would like some advice on the depths and types of foundation that you would recomend. Thank you very much Mr D L Smith
Any ideas for how to keep the trench in good condition, i.e. no crumbling sides, turning to muddy mess etc.