Piling and Integrity tests

turedPiling foundation

Foundations provide support for structures by transferring loads to soil or rock that have sufficient bearing capacity. Speaking broadly,  foundations can be categorised as either shallow or deep. Deep foundations are necessary where the bearing capacity of the surface soils is insufficient to support loads so the loads are transferred to deeper layers. Pile foundations are deep foundations, and are formed by long, slender, columnar elements, typically made from steel or reinforced concrete. A foundation is described as ‘piled’ when its depth is more than three times its breadth.

Pile caps

Piles can be used individually to support loads or grouped with a reinforced cap. The pile cap should overhang the outer piles, typically by a distance of 100-150mm on all sides. Pile caps can be linked together using a reinforced concrete ground beam. Capping beams are suitable for distributing the weight of the load-bearing wall. The capping beam should be kept clear of the ground where the purpose of the piles is to overcome the problem of the subsoil swell and shrinkage. This can be done by casting the capping beam on polystyrene or other compressive material, thereby allowing upward ground movement without damage to the beam.

Pile integrity testing

The majority of cast-in-situ piles fail because of defective pile shaft necking, intrusion of foreign matters, improper toe formation due to contamination of concrete base with soil particles, leaching of concrete, discontinuity of concrete, improper construction method or poor quality control. The pile integrity test is conducted before completion of pile caps, and ensures the proper functioning of pile foundations without failure. You can use sonic echo testing to test pile integrity after installation.

The integrity test enables a number of piles to be tested in a day. The information gathered is about the continuity, crack defects, necking, soil incursions, changes in cross section and approximate pile lengths. To carry out the test, a small but hard hammer is used to produce a light tap on the top of the pile. The shock travels down the length of the pile and is reflected back from the toe of the pile and recorded through a suitable transducer/accelerometer. The primary shock wave is reflected from the toe by change in density between the concrete and the sub strata. However if the pile has any defects within its length these will set up secondary reflections which will be added to the return signal. Normally more than one recording of signals is done until repeatability of signals is achieved.

Advertisements

Fire stopping

Section 10.2 of the building regs states; If a fire-separating element is to be effective, every joint or imperfection of fit, or opening to allow services to pass through the element should be adequately protected by sealing or fire stopping so that the fire resistance of the element is not impaired. In the case of a fire, passive fire protection helps seal gaps and stop the spread.

There are different types of opening that can compromise the integrity  of a fire resistant structure, like, opening for pipes, vent duct, flues etc. Where openings have to be created, they should be kept too a minimum, the smallest size possible and fire stopped.

Intumescent collars – These are designed for use on plastic pipes that pass through masonry floors and walls. The intumescent material expands inwards in a fire situation, to squeeze the collapsing pipe until the opening is completely sealed.

firecollar

Fire batt –  Fire batt is an insulation type material (Rockwool) which acts as an air seal barrier to reinstate the fire resistance and acoustic performances of concrete floors, masonry walls and dry walls systems, following the creation of voids for service passage. A 50-60mm thickness can give you up to 4 hours fire resistance. Where gaps of +10mm are apparent, fire batt is a more suitable solution.

fire-rated-batts-500x500

Intumescent mastic – Fire mastic is a versatile sealing solution to fill gaps and movement joints. When exposed to fire the intumescent sealant expands in volume to fill cavities. It also acts as a smoke seal. It is also suitable for sealing gaps between fire resistant walls, floors, between conduits and structural supports.

Intumescent foam – Where large gaps exist between the door frame and wall construction, conventional intumescent seals may not always be appropriate, but foam will. It can also be used for filling around ducts and other service penetrations, expansion joints and linear joints. Its flexible and will accommodate movement, yet is durable and resistant to extreme environmental variations. On activation the fire resistant foam degrades and the volume is replaced by an expanding mass of intumescent graphite which prevents the passage of smoke, flames and hot gasses.

44-pva_foam

RCD’s really help to reduce electric shocks

Each year around 70 people die and 350,000 are seriously injured by electric shocks. RCD’s are a life saving device which is designed to prevent you from getting a fatal electric shock if you touch something live, such as a bare wire. It can also provide some protection against electrical fires. RCD’s offer a level of personal protection that ordinary fuses and circuit breakers cannot provide. An RCD is a sensitive safety device which switches off electricity automatically if there is a fault.

An RCD monitors the electric current flowing through one or more circuits it is used to protect. If it detects electricity flowing down an unintended path, such as through a person who has touched a live wire, the RCD will switch the circuit off quickly. Fixed RCD’s are the  most common and are fitted at the consumer unit. This is the highest level of protection that can be provided from an RCD in a home.

It is important to understand how dangerous electric currents can be. An electric current passing through the body, particularly an alternating current (which is a current which reverses its direction many times a second at regular intervals) at power frequencies of 50 Hz and 60 Hz, may disrupt the nervous system causing a muscular reaction and a painful sensation. In a small number of cases, the consequence of an electric shock is death from cardiac arrest or respiratory arrest.

Current Building regulations requires RCD protection to be provided for all socket-outlets rated at not more than 20A. RCD protection should be provided for mobile equipment at not more than 32A.

The Victoria Tower of Westminster Palace

Victoria Palace

The Victoria Tower is the tallest tower in Westminster and stands out amongst the significant surrounding buildings of Westminster Palace. It is the square tower at the south-end of Westminster Palace. Built in 1855, it was once the tallest and largest stone square tower in the world reaching a staggering 325 ft. This is nearly 100 meters up. The Victoria tower is home to all of the Parliamentary Archives, so this sublime building surely is being put to excellent use with all those exciting documents its housing. Charles Barry was the architect who designed the Tower which has 14 floors. Each floor was linked via a single wrought iron Victorian staircase.

Cheap stone and serious decay

The Victoria Tower is part of the palace of Westminster, and was originally built with sand-coloured limestone from the Anston Quarry in Yorkshire. Anston stone was chosen to clad the cast iron framework, because it was cheaper and could be supplied in 4 ft blocks and lent itself to elaborate carving. The stone however, began to decay  as a result of atmospheric pollution from coal burning in London and the poor quality of the material used. You would think that buildings of such high prestige would have been built with a more durable stone, considering its regal connections. The defects of the stone became visible as early as 1849 and very little was done to prevent its decline during the 19th Century.

 

Restoration

A  large fragment fell off the Victoria Tower and nearly crushed a group of bystanders who were enjoying the smoggy Victorian views whilst munching on their roast beef sandwiches and fruitcake. Ok, that didn’t happen, but a large fragment did fall off and in 1928 it was decided that Clipsham stone would be used as part of the restoration. A honey coloured limestone from the Medwells Quarry in Rutland was chosen to replace the decayed Anston/ The restoration project was started in the 1930’s but halted due to the 2nd World War, and was only completed in 1960.

Cleaning

By the 1970’s, the effects of pollution were again visible, and a new programme of stone-cleaning and restoration was started in 1981. The North, west and South fronts, the river front and the clock tower were completed  by 1986. The Victoria Tower, whose cleaning was completed in 1994 was the last part of the exterior to be dealt with. The restoration of the Victoria Tower between 1990 and 1994, required 68 miles of scaffolding tube and one of the largest independent scaffolds in Europe. Nearly 1000 cubic ft of decayed stonework was replaced, and over 100 shields were re-carved on site by a team of stonemasons.

 

What are SAP’s ?

What are SAPs?

A SAP rating is the calculation that is required in order to produce a Predicted Energy Assessment and an EPC. Building regs require that a SAP calculation and an EPC is submitted for new dwellings prior to commencement of works.

A SAP calculation indicates a score from 1-100+ for the annual energy cost based on;

– The elements of structure

– The heating and hot water system

– The internal lighting

– The renewable technologies used in the home

The higher the score the lower the running costs, with 100 representing 0 energy cost. Dwellings with a rating in excess of 100 are net exporters of energy. SAP calculations allow comparison to be made of the energy running costs of dwellings anywhere in the UK. A SAP calculation is a desktop exercise, the client submits drawings, plans and specifications of the development to the assessor.

From the plans and drawings provided by the designer the assessor prepares numerical information which includes, the total floor area of the dwelling, the area of the lounge, the areas of heat loss floors, heat loss walls, heat loss roofs, dimensions of external windows, doors, storey heights etc.

From the spec provided, the assessor calculates the performance of the thermal elements. These are expressed as U values (U – values are the rate at which heat passes through a particular fabric.) The higher the U- value the greater the loss. The assessor then puts all of this data into the SAP calculation and considers; type of dwelling, floors, roof, walls, ventilation, energy efficient lighting, renewable technologies & hot water generation etc. The software determines whether or not the proposed dwelling complies with Building regulations. An air pressure test is usually required also. The SAP and air pressure test together are used to form and EPC.

 

Thermal conductivity of materials

Thermal conductivity, also is know as Lambda. Its the measure of how easily heat flows through a specific type of material, independent of the thickness of the material in question. The lower the thermal conductivity of a material, the better the thermal performance (i.e. the slower the heat will move across the  material).

It is measured in Watts per Metre Kelvin and if you were to use sheep’s wool to insulate your property this comes in about 0.034W/mk. The U-value signifies the heat loss through a given thickness of a particular material. The best insulating materials have a U-value of close to zero. The lower the better. The building regulations stipulate that for a new dwelling the elements must have the following U-values;

– Wall – 0.3W/m2k

– Roof – 0.15W/m2k

– Windows – 1.6W/m2k

U-values of solid walls

Most properties were built with solid walls before the 1930’s. Fuel was cheap, so energy efficiency wasn’t an issue, however heating a home can be expensive.

–  An uninsulated solid brick wall with a thickness of 225mm  will have a U-value of 2.70W/m2k.

– To insulate a solid wall you can either insulate internally or externally.

– 100mm of EPS insulation should bring the U-value down to 0.29 W/m2k.

– 110mm of rock wool insulation either side of a solid wall can achieve 0.036W/m2k. This has to be attached firmly to the wall and rendered.

 U-values of cavity walls

Cavity walls  became the norm in the 1930’s.  Until 1995 it is assumed that they were left unfilled.

– Unfilled  cavity wall before 1900 will have a U-value of 2.0, until 1975 a U-value of 1.6 & up to 1995 a U-value of 1.0.

– Filled cavity walls from up to 2002 had a U-value of 0.45, up to 2006, 0.35 and after 2010, 0.2.

Bricks, spoiled for choice

 

Facing bricks

Facing bricks are the most popular type of brick and have been the facade material of choice in the UK for thousands of years. They are primarily used for external walls of a building and are chosen for their aesthetic qualities. Facing bricks include any brick which is sufficiently hard burned to carry normal loads and is capable of withstanding the effects of rain, wind, soot and frost without breaking up.

Engineering bricks

Engineering bricks have high compressive strength and low water absorption. They are used for their physical characteristics and not their appearance. They are traditionally used in civil engineering projects and are most suitable for applications where strength and resistance to frost attack and water are important. Situations where they are used include, ground-works, manholes, sewers, retaining walls and damp proof courses. The two best known engineering bricks are the red Southwater brick and the blue Staffordshire brick. Both are very hard and dense and do not readily absorb water. The ultimate crushing resistance of engineering bricks is greater than 50N/mm2.

Engineering bricks are rated as class A or B with class A being the strongest. Class B engineering bricks are more common than class A bricks. They are both commonly a smooth red colour although blue engineering bricks are also widely available.

Common bricks

Despite their name, common bricks are actually the least common brick types in the UK. They tend to have lower compression strengths than facing bricks or engineering bricks and are generally lower quality. There is also less focus put into a consistent appearance on common bricks. Common bricks are generally used for internal brickwork only.

London stock brick

London stock bricks are a type of handmade brick used for a majority of building work in London. Its distinctive yellow colour and soft appearance come from yellow clay. London stocks are still made in comparatively small quantities in traditional brick works. Red stock bricks are also quite common, but the yellow or brown coloured bricks are usually known as London stocks. This brick is usually manufactured in Essex and Kent. They are made from clay composed of sand and alumina to which some chalk is added. The manufacturers grade the bricks as 1st hard, 2nd hard, and mild.

Stock bricks

The term stock brick can either indicate the common type of brick stocked in a locality or a handmade brick made using a stock. A stock or stock board is an iron-faced block of wood fixed to the surface of the moulder’s bench. The brick mould fits over the stock; the brick maker fills the mould with prepared clay and cuts it off with a wire level with the top of the mould; before turning out the ‘green’ brick onto a wooden board called a pallet for drying and frying.