Hints and Tips
How to work out how much loose material you need/remove
To work out how much material you will need to excavate or or to buy is calculated by the following.
Surface area x depth in (m) x density of material (tons m3) In(m2)
Density of the following materials Dry not water saturated.
Aggregates 1.7 to 1.8 tons per m3
soil 1.35 tons per m3
Concrete 2.2 to 2.4 tons per m3
So for instance is you have area of 50m2 and you want to cover it in gravel at 50mm thick you will need
50m2 x 50mm in meters is ( 0.05) x 1.7 = 4.25 ton of loose stone.
To skip or to grab away
Skips are expensive for what you get in them. The average 8 yard builders skip is around £180 in the north and midlands area with even higher rates to be expected in the south.
If your project is likely to generate more waste than 8 cubic yards of inert material its worth considering hiring a grab wagon. Grab wagons is a self loading pieces of plant which hold between 12 to 16 ton depending on the axle configuration. They generally work out around 1/2 to 2/3 the cost a skip per ton of waste removed.
A grab will work out cheaper if
- You have more than 8 cubic yard of inert waste to be removed.
- You don’t have an excavator on the job which can load a 38 ton tipper truck.
- Area to stock pile the spoil adjacent to the road or hard standing
The parameters for a grab.
- The wagon must be able to drive up the side of the stockpiled spoil.
- The waste must be inert.
- The ground under the stockpiled spoil may need protected from the scarping effect of the clamshell bucket used to load the wagon. For example plywood sheets over a grass covered lawn
How to work out what size skip will you need
Skips come in the following common sizes
Domestic use 2, 4, 5, 6, 8 yard
Commercial use 10 up to 40yard
Bulking up factor
The process of excavating a consolidated material will result in the material having voids and air pockets formed between each sod of dug ground. This difference in volume from what the material occupied compared to its excavated state is called the bulking up factor
To calculate what skip size you require for loose none self compacting material such as soils, dirt or clay is
Surface area x depth in meters x bulking up factor of 22% In m2
So for a drive that is 20m2 and to be excavated to 250mm deep we will need a 8 yard skip.
20m2 x 250mm depth in m is( 0.25) x 22% = 6.1m3
Skips come in cubic yards. To we need to convert cubic meters to cubic yard multiply 1.3
6.1 cubic meters x 1.3 = 7.93 cubic yards.
Its also worth informing the skip company as to what you are actually going to fill the skip with. Bricks, concrete and hard core if clean are all recyclable and can be sold by the skip firm once crushed. If you ask the skip firm they may even offer a reduced hire rate for clean inert waste.
Skips are generally heavy once they are full. They are especially so once filled with inert waste such as concrete. Its worth bearing in mind when you ask for a skip to be placed on your drive not only are you going to be putting the weight of the skip o your drive. But also the HGV used to pick it up.
The average combined weight of a wagon plus 8 yd skip and its contents will be around 18ton.
Skips can be positioned on highways with planning permission from the local council and a road fund permit. (Ask the skip hire company for details)
Bulk bags vs loose
Loose aggregates are generally sold by the ton. If you can accept a delivery for loose material then this will be the cheapest way to purchase any aggregate.
Industry defined bulk bag
Under guidance worked out by the BMF in conjunction with Trading Standards, bulk bags of aggregates should be filled to 900kg and must be marked with a minimum weight of 850kg.
In practice, the new trading standards, which the BMF developed for the benefit of the whole industry, not just members, means bags usually contain more than the 850kg, but less than 1 tonne
Choosing a construction professional
These steps should help you save time, money and stress when you’re preparing to get building work, renovations or repairs done on your home. They’ll also help you avoid problems with builders, plumbers or other contractors, eg decorators and electricians.
Step 1: Check if you need permission or approval
Step 2: compile a list of good builders or contractors with a proven track record
Step 3: Get quotes before you decide who to use
Step 4: Check their insurance are in place
Step 5: Get a written contract
Step 6: Be prepared to deal with problems