DSJ - SoE Construction Technology

Question 1

What is OSB board?

Answer 1

Oriented Strand Board - a type of engineered wood, similar to particle board, formed by adding adhesives and then compressing layers of wood strands in specific orientations. Produced in a variety of types and thickness.

Question 2

What codes of lead are there? What code did you use at Sutton?

Answer 2

Lead Code Thickness Weight (kg/m2) Uses

Code 3 1.32mm 14.97 Soakers

Code 4 1.80mm 20.41 Soakers, flashings, and
vertical cladding

Code 5 2.24mm 25.40 Flashings, flat roofing, parapet and tapered valley gutters, pitched roofs, vertical cladding, dormers, and bay roofs and canopies

Code 6 2.65mm 30.10 Flashings, flat roofing, parapet and tapered valley gutters, pitched roofs, vertical cladding, dormers, and bay roofs and canopies

Code 7 3.15mm 35.72 Flat roofing, parapet and tapered valley gutters, pitched roofing, dormers, and bay roofs and canopies

Code 8 3.55mm 40.26 Flat roofing, parapet and tapered valley gutters, dormers, and bay roofs and canopies

Question 3

What are BS documents

Answer 3

• Publications issued by British Standard Institution (BS)

- Give recommended minimum standards for materials, components, design and construction practices

Question 4

What are the three different types of basement construction?

Answer 4

a) Retaining wall and raft (monolithic) - slab raft foundation distributes building load. Basement walls are retaining.
b) Box and Cellular - similar to above but internal structural walls transfer and spread loads over raft, dividing basement into cells
c) Piled - superstructure load carried to basement floor by columns and treasferred into ground via pile caps & piles

Question 5

What are the three methods for waterproofing a basement?

Answer 5

Three methods are defined in BS 8102

“Type A” (barrier protection) which requires a tanking membrane

“Type B” (structurally integral protection) relies on the quality of the concrete structure only and is not suitable for all applications

“Type C” (drained protection) allows water into the structure, but collects it and drains it away from the occupied areas.

Question 6

What is involved in traditional underpinning?

Answer 6

Traditional underpinning involves digging pits underneath existing foundations. Only small narrow pits can be excavated at one time to avoid collapse. The pits are then filled with concrete and metal bars are set into their sides to allow connection between the different bays. Once the concrete in a bay is set, it is dry packed tight underneath the original foundations. The next bay can then be excavated and the process repeated. This form of underpinning becomes impractical when poor ground conditions or risk of ground shrinkage exceeds 2.5m in depth.

Question 7

What are the different types of piled underpinning?

Answer 7

Mini piling - involves drilling or shell auguring small diameter holes underneath the existing foundations, the piled holes are then filled with reinforced concrete.

Needle Piles - Piles can be formed inside and outside the building. The building is then supported using ‘Needle Beams’, spanning across the piles.

Double Piles - Can be formed outside the building/s. Cantilever beams are formed across the piles, set into pockets cut into the walls below ground.

Raft supported by Piles - Replacing the floor inside the building with a reinforced concrete raft supported on piles. Pockets are formed in the existing walls below ground. The reinforced raft is built into pockets to provide support to the walls.

Piles can be drilled in diagonally

Hydraulic jacks can be drive sectional pre-cast concrete piles into the ground from directly under the existing foundations.

Question 8

How would you sequence piles

Answer 8

In accordance with a sequencing chart - bays typically 1-1.5m but depends

Question 9

How do you ensure lead is satisfactory quality?

Answer 9

Compliant with BS EN 12588 - Certification required

Question 10

What did you specify for the abutment flashing at Sutton

Answer 10

Code 4 lead. Minimum 1.5m sheets. 100mm overlap. 75mm up-stand. turned 25mm into joint secured with lead wedges / clips at 450mm centres and where flashing pieces overlap. 150mm overlap over slates.

Question 11

What is dry lining?

Answer 11

The lining of walls with plasterboard sheets - Plasterboard can be fixed in a number of ways.

Question 12

What of the benefits of dry lining?

Answer 12

Creates a small void between the wall and plasterboard - useful for threading cables and an air void is a good insulator.

Thermal plasterboard and insulation can be used to increase thermal performance.

Dry plasterboard means quicker completion of wall finish

Question 13

How can dry lining be fixed to the wall?

Answer 13

Adhesive dabs - tend to be located around the perimeter of plasterboard sheets.

Fixing onto sawn timber batten frame (braced from floor to ceiling and sometimes preferred for uneven existing walls)

Fixing on a proprietary metal channel (metal during system). Light gauged metal channels fixed to the walls using adhesive. Centres of channel correspond to width of plasterboard. Plasterboard is fixed using self tapping screws.

Question 14

How did you conceal joints between the plaster board and the door linings?

Answer 14

Architrave

Question 15

What dry lining system did you use at Capesthorne?

Answer 15

Plasterboard with taped joints

Foil back Rigid insulation panels fixed onto sawn timber batten frame (vert DPC inc). Foil tape to joints forming VCL

U-Value - 0.28Wm2K

Question 16

What waterproofing system did you use for Knutsford?

Answer 16

Walls - Wall membrane, secured using plugs (e.g. Newton Multiplug). Insulation (Rigid and foil backed). Metal furring system (Freestanding) and plasterboard.

Floor - Rigid insulation with waterproof membrane and screed on top. Drainage channels provided between the insulation connected to a sump / pump.

DPM made to create a 10mm channel to the base of the walls to allow drain into channels.

Provided prescribed specification and detailed drawing.

System is backed up by Independent Guarantee. Manufacturer installed system to ensure garuntee eligibility

Question 17

How do you calculate U-Value?

Answer 17

The R-Value refers to a material’s ability to resist heat transfer at a certain thickness

The R-Value is calculated as R = l/λ where l = the thickness of the material in metres and λ (lambda) is the thermal conductivity of the material in W/m.K.

U-Value (of building element) = 1 / (Rso + Rsi + R1 + R2 …)

where Rso is the fixed external resistance, Rsi is the fixed internal resistance and R1, R2 etc. are resistivity of all elements within the application, including that of cavities within the construction.

However thermal bridging factors of fixings or stud work should also be considered.

Question 18

In Runcorn, how did you propose rectifying the settlement?

Answer 18

Underpinning - Mass concrete, expanding foam or mini-piling

Rebuilding as light weight structure - timber frame?

Removing

Question 19

In Runcorn, why did you consider a repair was necessary?

Answer 19

The extent of the cracking

Question 20

In St Helens, detail the wet room system you specified

Answer 20

Suspended timber floor - a floor former (providing fall) or ‘dec’ can be fitted, and the drainage systems and waterproofing membranes can be installed.

Question 21

What types of tanking products are there?

Answer 21

Tanking products include:

cementitious coatings
bituminous coatings
membranes
paints
sealants

Question 22

What alternative wet room system did you suggest for St Helens?

Answer 22

As there was an existing solid floor I proposed removal of the old screed in the designated shower area to allow the new drainage system and screed to be installed with the required drainage falls (1:40 to 1:110). It is also possible to remove the screed within the shower area to allow the drainage outlet to be fitted, self-levelling latex to be poured, and a floor former installed on top. This will form the wet room gradient (12mm minimum). Tile safe flexible wall and floor membrane and pvc boarding and vinyl floor.

Question 23

What are the stages of design & construction from inception to completion?

Answer 23

Stage 1 - Inception.
Stage 2 - Concept and Viability.
Stage 3 - Design and Development.
Stage 4.1 - Local Authority Drawings.
Stage 4.2 - Construction Documentation and Tenders.
Stage 5 - Construction.
Stage 6 - Close Out.

Question 24

Tell me about your understanding of operational and maintenance processes.

Answer 24

Operations and maintenance typically includes the day-to-day activities necessary for the building/built structure, its systems and equipment, and occupants/users to perform their intended function.

The difference between operations and maintenance is operations is the activities you perform to reach business objectives, whereas maintenance is everything you do to keep equipment in running order.

Question 25

Tell me about how construction design solutions vary for different types of buildings, such as clear span or acoustic requirements.

Answer 25

‘Clear Span’ is an architectural term to describe the distance between the two inside surfaces of the span supports; the distance that is unsupported, if you will. If you have need in your steel building design for a wide space that is clear of posts and beams, then a clear span design is the choice for you.

Question 26

Talk me through the RIBA stages of work.

Answer 26

0 – Strategic Definition.
1 – Preparation and Briefing.
2 – Concept Design.
3 – Spatial Coordination.
4 – Technical Design.
5 – Manufacturing and Construction.
6 – Handover.
7 – Use.

Question 27

How have you liaised with specialists and consultants to develop project specific design and construction solutions?

Answer 27

I liased with a geotechnical engineer and water proofing speacialist whilst designing the tanking system at Knutsford.

The specialist can be a manufacturer but only if they have experience in all of the aspects of waterproofing. In reality they will not be able to give unbiased advice. You must take into account the repair ability of the chosen system and the feasibility of remedial measures must be assessed.

Question 28

Talk me through how you have reported on the impact of different design solutions on cost of a construction project.

Answer 28

Withy bank I reported on how a new structural floor could be build to provide a first floor.

Knutsford I recommended use of a 0 rated timber staircase.

Question 29

Talk me through how when you have reported on the impact of different design solutions and construction processes on programme.

Answer 29

Missing chimney breast to GF of Knutsford - Gallows brackets, rebuilding etc…

Question 30

Talk me through when you’ve advised on the choice of construction solutions for your project.

Answer 30

Staircase at Elsterne
EIR system for Stables 
Dry lining to Capesthorne
Compartmentation at Elsterne 
Ventilation gap - case study and Runcorn. Foil backed PIR, tight friction fit between the rafters. Insulated backed Plasterboard. Counter batten to provide min 50mm air gap on cold side. Gyproc Drywall Sealer/ VCL on warm side of insulation / Foil back insulation and foil tape at joints / Insulated back PB and foil tape at joints. Breathable membrane. Vented soffits and ridge tiles.

Question 31

Talk me through when you have advised on potential programme reduction in respect the construction of a work package or activity.

Answer 31

See case study

Question 32

Talk me through a value engineering you’ve carried out during a construction project.

Answer 32

See Case Study. Replacement of the roof covering, identification of Spanish slate as a feasible replacement.

Question 33

How have you advised on design where the methods of construction or materials have had a significant impact on project cost?

Answer 33

At Wallasey - Value engineering - I suggested on the adoption of Easi-joist system to save costs by reducing labour time, i.e. drilling into joists for services.

Question 34

Detached house, Runcorn - talk through what options you considered in relation to the differential settlement.

Answer 34

Mass concrete underpinning and other underpinning solutions

Removal of the porch

Question 35

Withy Bank dwelling - talk through your role on this project.
You mention you advised In relation to the suitability of the existing structure for conversion. What did you consider in relation to this? What were your recommendations to the Client and why?

Answer 35

The building was steel portal frame construction, originally designed to certain limits. Initial structural calculations would not have allowed for the addition of a first floor. I advised on potential solutions to this problem:- i.e. Appointment of a structural engineer to assess the capability of the existing portal frames and alternative solutions.

Depending on the outcome of the survey and decisions about strengthening the structure, there are two pairs of options, with two choices each. The first choice is whether to impose additional new loads on the existing structure (the insulation, internal finishes, new internal floors, services etc), or whether the existing structure takes little or no more than the existing arrangement, and the additional loads are borne on their own, structurally independent foundations.

Question 36

Basement flat, Knutsford - run through your role on this.
Did you specify the tanking system? If so, what guidance did you use? What options were considered and discounted as part of your design?

Answer 36

I prepared a prescriptive specification for the system.

Adopted a team based approach to the design with consultation of a specialist waterproofing contractor (UKAS accredited).

The building had previously been tanked incorrectly. The installation was retrospective. BS8102 type A and C system adopted. Membrane and channel drains

Question 37

How do you use your knowledge of construction technology to inform the following; estimating, production of pricing documents, compilation of tender and contract documents, interim valuations, valuing change and compiling final accounts?

Answer 37

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Question 38

Tell me about what you think in relation to various types of materials affecting the cost and time of the project?

Answer 38

Timber staircase - Knutsford

Question 39

What construction materials have you worked with?

Answer 39

Brick, timber, Slate, PVC gutters

Question 40

How do you prepare annotated sketches and specification detailing how elements interact?

Answer 40

Prepare a prescribed specification alongside detailed drawings.

Question 41

What mechanical and electrical services are relevant to your area of work?

Answer 41

Predominantly domestic electricity, extract fans and heating systems. I provide performance based specifications for these items and so the contractor can design.

Question 42

What distances are required between dwellings with windows and habitable rooms

Answer 42

The rear window to rear window distance between any habitable rooms (living rooms, bedrooms or dining rooms) should be at least 21 metres in situations where first floor windows of separate properties face each other.

Question 43

For Wallasey did you design the waiting area in accordance with building regulations relating to buildings other than dwellings?

Answer 43

No as it is still within the dwelling. Public cannot entire freely. We did provide disabled toilet facilities.

Question 44

How did sustainable energy consultant alter the design?

Answer 44

Plant room space required - layout
Underfloor heating - raising floor level.
Oversized radiators.

Question 45

Walk me through Withy Bank your involvement with Withy Bank?

Answer 45

We were instructed to provide drawings for conversion and provide a suitability for conversion survey.

Client requested a first floor to provide additional space. After experience of previous projects and an awareness that the existing structure was not designed to accommodate such loads I instructed a Structural engineer to provide the necessary calcs.

Conversion Class Q GPDO - Checked requirements with Planning department. Limitations include; The barn or agricultural building must have been in a use solely for agricultural uses on or before 20th March 2013.

Size can build Smaller (up to 100m2) of larger 100m2 to 465m2 dwelling houses

As from 1st August 2020 you must supply floor plans as part of the application and it will require the the provision of adequate natural light in all habitable rooms of the properties created under Class Q. The GPDO defines a habitable room as any rooms used or intended to be used for sleeping or living which are not solely used for cooking purposes, but does not include bath or toilet facilities, service rooms, corridors, laundry rooms, hallways or utility rooms. Note that from 6th April 2021 you will need to adhere to minimum space standards – this is for any prior approvals that are submitted after this date.

Question 46

What are requirements for disabled toilets?

Answer 46

Part M of the Building Regulations

According to Document M of the UK building regulations access to and use of buildings other than dwellings, wheelchair users should be able to comfortably approach, transfer to and use the sanitary facilities provided within a building. This requires the provision of a wheelchair-accessible unisex toilet.

The recommended dimensions of a disabled toilet room are at least 2200mm Deep x 1500mm Wide.

Rooms larger than these dimensions will provide a larger turning circle for use by wheelchair users, which in turn will provide additional comfort and ease.

Question 47

Walk me through the process of mini piling

Answer 47

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Question 48

What is BS 8102?

Answer 48

It is essentially a document that outlines best practice when planning a basement waterproofing scheme, advising the designer on the various methods of waterproofing available and the correct way to ‘specify’ them for contractors, ensuring a successful and long-lasting installation.

Question 49

What does BS 8102 require prior to design?

Answer 49

The code highlights the importance of
undertaking a desk study to establish the
following;

a) “to assess the geology and
hydrogeology, including soil
permeabilities, flood risk, radon,
methane and other ground gases
and contaminants (e.g. chlorides
and acids);

b) to assess the topography of the
surrounding ground in relation to
the below ground structure;

c) to establish the likely highest level of
the water table and the potential for
the occurrence of a perched water
table; and

d) to identify any missing ground and
groundwater information, which
should then be obtained by
undertaking a site investigation in
accordance with BS 5930 and BS EN
1997.”

Question 50

What should BS8102’s risk assessment also consider?

Answer 50

“Risk assessment should also consider:

a) the effects of climate change, burst
water mains and sewers, adjacent
trees, sulfates, radon, methane and
other ground gases and
contaminants; and

b) where external drainage is
proposed, the effects of drawdown
on adjacent structures, the potential
silting of drainage and biofouling
issues.

Even when the site investigation indicates dry
conditions, the risk of some water logging (see
Note 2) in the future should be assumed.”

Question 51

What are the Water Table Classifications?

Answer 51

High – where the water table or perched water
table is assessed to be permanently above the
underside of the base slab.
Low – where the water table or perched water
table is assessed to be permanently below the
underside of the base slab. This only applies to
free-draining strata.
Variable – where the water table fluctuates.

Question 52

At Knutsford. What did you consider before design of the tanking?

Answer 52

The Code states the need to inspect existing
structures carefully before any risk assessment
is completed and the waterproofing system is
specified or installed. This is essential to ensure
the suitability of the structure for the proposed
waterproofing and to identify defects or
conditions affecting walls and floors that may
affect the performance or effectiveness of any
waterproofing system.

Question 53

What are Easi Joists

Answer 53

easi-joists® are parallel chord trusses using stress-graded timber chords, plated together with Wolf Systems’ patented, precision engineered metal webs, EP 1 985 774 A1 – the strongest available on the market. easi-joist® offers unrivalled lightness, strength, and greater clear span ability.

Question 54

At Knutsford, why did you adopt a water resisting design?

Answer 54

Even when the site investigation indicates dry conditions, the risk of some waterlogging in the future should be assumed’ and that: ‘Even in a permeable subsoil, groundwater requires time to drain away and this can result in limited pressure periodically coming to bear against the structure”.

Waterproofing measures should be designed
on the basis of water to the full height of the
retained ground at some time during the
structure’s life where:
a) no detailed geological or
hydrogeological assessment has
been undertaken;
b) the results of the soil investigations
are inconclusive with respect to
groundwater;
c) the ground drainage characteristics
are unreliable;
d) the drainage measures (either
internal or external) are unreliable
or un-maintainable and infiltration
cannot be controlled.
This passage is significant because it removes
any ambiguity that may have surrounded the
structural considerations and the expected
head of water that can be expected to come to
bear on the structure.

Question 55

What are the three sources of water?

Answer 55

It is made clear that water from the following
three sources should be considered and that
any waterproofing should provide protection
from -
1) the inflow of surface water, ranging
from percolation of rain to
inundation of water from burst
water mains.
2) the water pressures acting on the
external retaining wall system;
3) the water pressures below the base
slab.

Question 56

What are the grades of waterproofing?

Answer 56

“Grade 1 - Car parking, plant rooms (excluding
electrical equipment), workshops. Some
seepage and damp areas tolerable, dependent
on the intended use
Grade 2 - Plant rooms and workshops requiring
a drier environment (than Grade 1); storage
areas. No water penetration acceptable. Damp
areas tolerable; ventilation might be required
Grade 3 - Ventilated residential and
commercial areas, including offices, restaurants
etc, leisure centres. No water penetration
acceptable. Ventilation, dehumidification or air
conditioning necessary, appropriate to the
intended use.

Question 57

Is a specialist required to assist in a tanking design?

Answer 57

BS8102 now therefore asks for a waterproofing specialist to be included as an integral part of the design team to ensure that an integrated waterproofing solution is realised.

Criteria outlined in the standard are that the individual be:

Suitably experienced
Be capable of devising solutions that accommodate the various projects constraints and needs
Provide the design team with information and guidance that assists with and influences the design, installation and future maintenance of the waterproofed structure