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DO-IT-YOURSELF
RE-STUMPING CHECKLIST
Re-stumping
- also known as re-blocking in Victoria - is a multi-million dollar
business in Australia and unfortunately very few people are aware
of the many potential pitfalls in this trade.
Contractors asking for advance payments then
disappearing, unexpected damage to walls, windows and plumbing,
work having to be redone, squeaking floors, and floors which are
more crooked after having been stumped are only some of the problems
reported to Archicentre by people who have been caught out, or
who have been victims of unscrupulous operators.
In some States, houses with timber floors built
more than 30 years ago will mostly have their floors supported
on timber stumps. The life expectancy of these stumps can vary
from 20 to more than 80 years depending on the type of timber,
soil conditions and external influences such as surface drainage
and insect attack.
In the course of its inspections, Archicentre
has found that up to 30% of timber stumped homes investigated
needed immediate re-stumping either partially or completely.
Checking your stumps
Before undertaking renovation work on
older homes, it is essential to check the condition of the stumps.
Many people have watched in dismay as newly completed alterations
have been virtually destroyed as the structure subsides.
In brick houses, where the bearers are supported
on brick piers at the ends, rotten stumps will cause a 'trampoline'
effect in the centre of rooms. Contrary to popular belief, the
condition of stumps in weatherboard homes cannot be definitely
confirmed by jumping on the floors.
If the stumps have rotted evenly, the floors
may appear firm, however they will almost always slope away from
brick fireplaces. Other symptoms are crooked door and window frames.
It should be remembered that these symptoms are
only evident after the stumps have failed completely. A house
may appear quite sound during a visual inspection, but could start
to sink shortly afterwards if the stumps have just reached failure
point.
The condition of stumps can be ascertained by
scratching away 50mm to 100mm of soil from the base of the worst
stump to check its condition below the ground.
Stumps deteriorate most quickly in wet conditions
and generally the worst stumps are those with the highest and
most prominent water marks.
If only a few appear faulty, individual replacement
may be the best solution. However, if more than 20% to 30% of
stumps show serious deterioration, total re-stumping should be
considered.
In Victoria, bulky sub-floor heating ducts can
often hamper proper investigation of stumps and supporting walls.
Walls and stumps are sometimes removed when ducts are installed,
without it being obvious, leading to structural problems.
If you are contemplating installing central heating,
the possibility of this happening to you should be considered.
Selection of stumps - Victoria
The first decision to make is to choose
the most suitable type of new stumps. Rot-resistant timber stumps,
like Victorian red gum are still quite commonly used. Their advantage
is that they are still sometimes 10% cheaper than concrete, and
although they have the disadvantage of limited life expectancy,
this will not affect occupants living in the house for less than
20 years. Perhaps the biggest disadvantage is that timber stumps
cannot be as firmly secured to the bearers as concrete stumps
so that re-leveling may not be quite as accurate.
Concrete stumps are available in several types.
The concrete stump with the most positive form
of connection is the one with a 10mm diameter threaded rod at
the top secured with a poured concrete pad footing. The threaded
rod allows the stump to be bolted to the floor frame preventing
both upward and downward movement. The concrete pad will provide
protection against long term footing settlement.
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A further advantage is that by tightening
the nut after the concrete pad has set, and by partially
cutting the bowed bearers at their high points, high spots
in the floor can be pulled down.
Concrete stumps will last indefinitely except in extremely
damp conditions where the metal reinforcement in the stump
rusts and expands, causing weakness. This also applies in
Queensland.
LEFT: FIRST STAGE OF RE-STUMPING
It may be necessary to remove several floor boards to gain
access to the stumps
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Selection of stumps - Queensland
Stumps in the past were made of 300mm
diameter ironbark or similar rot-resistant timber. Now CCA (copper
chrome arsenate) treated pine, or concrete stumps are used.
The most positive form of connection to the bearer
is a bracket fixed to the stump by a coach screw or bolt. The
other end of the bracket is anchored to the bearer by a threaded
end and nut. This is also a positive form of stump/bearer connection.
In cases where the ground is unstable (soft), a concrete footing
is sometimes poured.
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Because of high wind stresses, anchor bolts are required
at each corner of a Queensland house, around the perimeter
every four metres and under bracing walls. These bolts are
also needed in high wind areas of Victoria.
RIGHT : THE FLOOR AFTER RE-STUMPING
Both concrete and timber stumps are shown
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Selecting the right contractor
Having chosen the most appropriate stumping
system, extreme care should be taken in selecting a reliable and
experienced contractor.
The contractor should have enough hydraulic jacks
to lift the building in one or two sections. Generally one jack
is required for each stump and there are about 80 stumps in an
average 150 sq. metre (16 square) timber house, less for other
types of housing like brick veneer (approx. 60). If too few jacks
are used, the house will need to be lifted in several sections,
which will cause severe and costly damage to plasterwork and framing.
In choosing the contractor, the following points
should be made clear when obtaining quotes. These points should
also form the basis of a contract between the client and re-blockers:
- The type of stumps (and pads, if appropriate)
to be used.
- The spacing of stumps.
- That on completion the floors will be brought
reasonably back to level, say within 10mm.
- That the work will be in accordance with the
relevant building regulations.
- That a council building permit will be obtained.
- The agreed cost.
- The start and expected completion date.
- That if floorboards must be removed, to what
condition the floor will be reinstated and whose responsibility
it is to remove and replace coverings.When comparing quotations
from several contractors, ensure that they all include the same
items. The lowest price may only be indicative of a lesser number
and poor choice of stumps, which may spell disaster in the long
term.After receiving the quotes, check the bona fides of the
contractors by asking them to give you the names and telephone
numbers of one or two people they have recently done work for.
Check that these people are happy with the work, and you may
even ring the local council's Building Surveyor in the area
where work was carried out and make sure that the council was
satisfied with the job.
After the work has commenced, it is essential
that it be supervised carefully. The most common faults are:
Floors not properly re-levelled. This should
be thoroughly checked with a spirit level, or preferably, a dumpy
level.Stumps not being securely fixed to bearers, (this may eventually
result in a noisy floor). Stumps not positioned directly underneath
the joining of two bearers.Stumps not centrally located over pads,
where pads are used.Failure to provide ant caps between stumps
and bearers.When new stumps have been installed and the jacks
removed the holes should be back filled with well-compacted earth.
The final payment to the contractor should be
made only after all work has been completed according to the contract
and has been found to be satisfactory.
Remember, the best way of avoiding
expensive problems is to be aware of them before you purchase
your house or before you undertake repairs and renovations. Archicentre
has carried out thousands of home inspections for home owners
and prospective buyers, to help them make a realistic appraisal
of the property before buying, renovation or repairing.
BOOK
AN ARCHICENTRE INSPECTION
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