Avocet Pde OPW - App E Slope · OPW20/0092

 

exend ourwards a minimum of 900 mum (more in highly reactive
soil) and should have a minimum fall away from the building of
1:60. The finished poving should be no les than 100 mm below
brick vent bases.

Tis prudent ro relocate dminage pipes away from this paving, If
possible, to avold complications from future leakage If this is nor
practical, earthenware pipes should be rephiced by PVC and
backfilling should be of the same soil rype as the surrounding soil
and compacted to the ame density.

Except in areas where freezing of water is an Issue, it is wise to”
remove taps in the baikting area and relocate chem well away from
the building — preferably moe uphill from ir (see BTF 19).

Tc may he desirable to install a grated drain at the curside edge of the

paving on the uphill side of the building. Ifsubsall drainage is
needed rhis can be installed under the surface drain,

Condensation

In buildings with a subfloor void such as where bearers and joists
support flooring, insufficient ventilation creates ideal conditions for
condensation, particularly where there Is little clearance between the
floor and the ground. Condensation adds to the moisture already
present in the subfloorand significantly slows the process of drying

Warning: Although this Building Technology Pile deals with
cracking in buildings, it should be eid thar aubfloor moisture can

result in the development of other problems, notably:

© Wacerthar is tearumiteed into masonry, metal or timber building
elements causes damage and/or decay two those elements.

* High subfloor humidity and moisture content create an ideal,

* Where high moisture levels are transmitted co the flooring and
walls, an increase in the dust mite count can ensue within the
living areas. Dust mites, as well as dampness in general, can be a
health hazard two inhabitants, particularly those who are
abnormally aasceptible to respimrory ailments:

The garden

The ideal vegetation layour is to have lawn or plants thar require only
light watering immedianely adjacere to the drainage or paving edge,
then moce demanding planes, shrubs and trees spread our in thar order.

Overwarering due to misuse of avomaric watering symems iso
common canse of sarusarion and water migration under footings. If ic
is necematy to use these systems, it is important w mmove garden
beds to a completely safe distance from buildings.

Existing trees

Where a tree is canting a pooblem of soil drying or there is the
existence or threat of upbeaval of footings, if the offending mow are
subsidiary and their removal will not significantly damage the tree,
they should be severed and a conceete or metal harrier placed
vertically in the soil w prevent fucure coor growth in the direction of
the building, If it is not possible to remove the relevant mors without
damage tw the tree, an application ro remove the ree should be made
to the local authority, A prudent plan is wo transplan likely offenders
before they become a problem.

regarding root pacterns, volume of water needed and safe distance
from buildings of most species. Boranic gardens ace also sources of
information. For informarion on plant mow and drains, see Building
Technology Pile 17.

Excavation

Exravation around footings must be properly engineered. Soil
supporting foorings can only be safely excavared aran angle thar
allows the soil under the footing to remain stable. This angle is called
Deano ween fe Biren sat eclos between soil
ype and conditions Removal of sail within che angle of repose will
cause subsidence.

Where erosion has occurred that has washed away soil adjacent ro
footings, soll of the same classification should be ionroduced and
compacted to the same density, Where footings have been
undermined, augmentation or other specialist work may be required.
Remediation of footings and foundations is generally the realm of a
specialie consulrant.

Where isolated footings rise and fall because of swell/shrink effect,
the homeowner may be remperd to alleviate floor bounce by filling
the gap thar has appeared between the bearer and the pier with
blocking. The danger hese is thar when the next swell segment of the
cycle occurs, the ertra blocking will pash the floor up inno an
accentuated dome and may also cause local shear failure in the soil. If
I is necessary to use blodeing, Ic should be by a pairof fine wedges
and monitoring should be carried our fortnightly,

This BYF was prepared by John Lewer FAIB, MIAMA, Partner,
Construction Diagnosis.

‘The infermation in this and other Issues in the series was derived from various scuross and was beteved to be correct when pubished.

 

The Information ts advisory. it is provided In good falth and not clained io be an exhaustive treatment of the relevant subject.

 

 

Further proteasional odvice needs to be obtained before tahing any action based on the information provided.
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