NOOOOOO! WONT DO THIS APPROACH, a big rabbit hole here lol...
Too long, too boring... too already available lol
Much better utilising our Partners/Participants etc and making things more accessible with links to stuff like this
Considering the large number of villas constructed, there was a wide variation in construction details and materials used, so careful site investigation is always recommended.
Review the state of the existing building, identify the problems and work out what you want to achieve and how you want to live – within your budget!
TYPICAL PROBLEMS:
DESIGN & LAYOUT
STRUCTURE: Undersized structural members (rafters, floor joists, limited wall bracing, roof and subfloor, sagging of joists or bouncy floors) or potentially dangerous structures (typically, brick chimneys with lime mortar)
FOUNDATIONS & SUBFLOORS: Some unevenness in the floor leading to out of square doorways and window openings, lack of ground clearance under the floor or poor ventilation of the subfloor and possibly wet ground under the building
ROOFING & WALL CLADDING: No wall or roof underlay, cracking in masonry, rising damp (around brick chimneys and within the walls of brick villas) or corrosion of metals such as head flashings and fixings
FLOORING Replacing original flooring or adding insulation.
EXTERNAL WALLS & CEILINGS: Insulation (such as double/triple glazing into existing sashes), incorporating hard lining, walls that re out of plumb or corners not square, cracked plaster ceilings, draughts or jammed windows and doors (through settlement, paint build-up or broken sash cords).
WIRING: Replacing insufficin r unsafe wiring
PLUMBING: Low water pressure or damaged terracotta sewer and stormwater drains (through fracturing, failed joints or tree root intrusion)
MOISTURE: Weathertightness or internal moisture
BORER, ROT & MOULD
MATCHING NEW TO OLD: Framing sizes, timber profiles, roof tiles or glazing that are no longer available
HEALTH RISKS: Asbestos or lead
FIRE SAFETY
TECHNICALLY SPEAKING
An introduction for this more TECHNICAL SECTION This will be more about detail and include various links to valid aspects etc. This is the section that will need to be updated on a regular basis.
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DESIGN
Consider the original design and layout (& any subsequent alterations) which may or may not include:
Indoor/Outdoor flow
Good orientation of living spaces to the sun or views
Good levels of natural light (although north-facing rooms with bay windows are generally well lit)
Internal gutters (can be prone to leaking and may have insufficient fall)
Enough power outlets and light fittings
Garaging
Universal Design elements
Access to side walls for maintenance/repairs
Compliance with current RMA constraints
FOUNDATIONS & SUBFLOORS
Old villas may have uneven/non level floors.
The earliest New Zealand homes were generally built on flat, good bearing capacity land, but as our cities expanded and the suburbs crept into the surrounding hills, onto reclaimed land or onto drained, swampy areas – the ground's bearing capacity was compromised.
As part of a general inspection, all floors should be checked to make sure that no movement has occurred. In most instances of foundations failure, the signs will be obvious in the unevenness of the floor.
Look out for:
Rotten timber piles
Missing piles or bearers (previous alterations may have included their removal to provide storage space under the floor).
Soft ground conditions tha have allowed the pile to sink.
The villa wasn't levelled when repiling.
The span for the floor joists is too big, causing them to sag.
Rot in wall framing supporting an upper floor.
Deterioration of foundation piles and/or subfloor framing can be caused by rot or wood-boring insects.
Generally, the perimeter piles are the first to deteriorate. Usually, chimneys based on concrete/brick foundations remain sound so that the floors tend to ‘hump’ and slope away from them.
BAD GROUND: More infrequently, uneven floors may be due to subsidence of the foundations because the home was built on unstable ground such as: deep organic topsoil, peat, soft or expansive clay, uncompacted fill.
In these cases, it's likely that the heavier elements, such as chimneys, masonry and brick walls may have sunk, cracked and be out of plumb. In cases of subsidence, obtain the advice of a qualified structural engineer.
LEVELLING: The most effective way to correct a floor that is out of level is to employ a firm experienced in this work to jack the sunken parts of the building back to as near level as possible. The piles and/or damaged subfloor can then be replaced to reinstate the building in the level position.
RONNIE, below is just a wee example of potential pull out video within the technical section. In this case it's a video, but will do a similar one for links to other sites etc. I actually know this chap and he could be VERY useful re the Reno Guide, will chat with Bob.
This process may result in consequential damage to wall linings. In some cases, doors and windows will need to be eased as the building sank and will require remedial work after the jacking. An assessment must also be made of the effect of jacking on additions, alterations, fittings and services added to the building after the floor sank.
IF JACKING IS NOT POSSIBLE: The floor may be left as it is, if acceptable to the owner, overlaid by a new timber, plywood or particleboard floor packed up level, or where there's a “hump’ in the middle of a room, it can be levelled by removing the centre piles and allowing the centre of the floor to settle with the perimeter walls.
REPILING
Rotted timber should be replaced with H5 treated timber or precast concrete piles.
New treated timber or concrete piles can be installed:
From under the floor where there is sufficient working space (minimum 450mm2)
From above the floor by cutting holes (approximately 450mm2)
When replying in soft ground, it's sometimes necessary to install deeper piles in order to reach firmer ground. These can be small diameter steel rails that are coated to resist corrosion. They are driven or augured down to the required level and then a concrete pile is cast around the top. In extreme cases where the house is built on deep unstable ground, it may be necessary to remove the roof so that the long piles can be driven down to firmer ground.
Soft ground conditions are usually the result of wet soils so the renovation needs to address the cause of the dampness. Once the soil dries, bearing should return, but sometimes it may be necessary to install additional bearer to remove the load from the offending pile.
If there's a gap between the pile and the bearer or both are basically sound but thee's signs of moisture on the bearer, the bearer can be jacked up off the pile (after cutting any fixings), a DPC inserted into the space and the bearer lowered and refined.
Repiling carried out since the 1920's and before the introduction of H5 treated timber is likely to be concrete piles with the bearers tied with galvanised wire to the concrete pile. Any original connecting wires are likely to be corroded and of limited structural value – so replacement will be required.
INADEQUATE FOUNDATION BRACING
Section 5 of NZS 3604 requires foundations to be adequately braced but existing foundation designs may not comply with this requirement. It's likely that a significant number of villas will have already been replied, although some with original foundation remaining. Typically, when a villa was repiled (certainly if done pre-1980's), it was unlikely support or bracing was provided to the new piles.
Bracing can be provided by a combination of:
Anchor piles
Cantilevered driven piles
Permeter footings
Timber bracing between piles
With most suspended floor construction, it's possible to provide diagonal braces between adjacent piles or between piles and bearers/joists. Modern 12kN pile fixings may be able to be used, or the connection can be made with M12 hot-dip galvanised bolts. Another option is to embed a number of piles more deeply into the ground, typically 900mm for an anchor pile in accordance with NZS 3604 – how many depends on the size of the house and the local earthquake and wind zone.
If a floor is springy because the span is too large for the timber sizes, a new bearer and piles at mid-span can be added to provide more support. For first floors, the installation of support beams can be one option, but this must be integrated with structural changes to the ground floor where the plan of the building is being modified.
INSUFFICIENT GROUND CLEARANCES
Many villas are built much closer to the ground than permitted by the current Building Code. While the original villa may have sufficient clearance, it's common for the clearances to be significantly less under the lean-to addition (especially on a site that slopes to the front of the house).
A lack of ground clearance may not cause a problem provide the soil under the villa is dry and/or if there's sufficient ventilation.
Renovation options to address lower than minimum ground levels can include:
Reshaping the land around the perimeter of the building to slope it away from the building so that water can't drain underneath
If the buidling is to be repiled, consider lifting it to increase the clearance. This may also be done to create additional floor space or a garage below.
A concrete floor slab laid over a DPM
Incorporating a change of level into the planning of the addition
Getting permission from the BCA as an alternative solution to match the existing floor levels, but specifying timbers with higher levels of treatment or natural durability and covering the ground with polythene to reduce moisture evaporation into the subfloor space.
Ronnie, this does on for a lot, need to discuss how this sort of thing is handled. If we do actually use BRANZ, we should obviously acknowledge, but obviously all information will need to be updated!
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