Note: Descriptions are shown in the official language in which they were submitted.
1302145
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DIVERTING GROUND-BORNE GASES F'ROM BUILDINGS
This invention relates to a system for preventing gases
whlch are present in the ground from entering the basement
of a building.
Bac~kqround to,~h~ Inven~lon
It has long been the practlce of many local authoritles to
dump commercial and household xefuse in disposal sites on
the outskirts of the city. As a city expands, however~
lnevitably some buildlngs come to be erected on, or near to,
the slte of the burled garbage dump~.
Norma~y, thls poses no problem. Sometimes however, and
this may not happen until the building has been occupied for
a considerable tlme, the occupants begin to notice
ob~ectionable ~me~s pervading the bullding, especia~y ln
the basement of the building. These sme~s can be traced to
the decomposing rubblsh. The gases can ln some cases travel
a considerable di~tance underground away from the dump.
Natura~y, lf the smell~ problem had been anticlpated, the
bulldlng would elther have been erected elsewhere, or would
have been con~tructed ln such a manner as to seal out the
gases that cause the smells.
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Once the sme~s develop in a building, the màrket value of
the building is drastica~y reduced unless the problem can
be cured.
The inventlon provldes a system for rellevlng the basement
smells problem ln exlsting building~ that have been erected
too near to a buried garbage dump, or other source of
qround-borne gase~.
Genera~ E~ snLQ the Inven~lQn
The human nose ls extraordlnarlly sensltlve. The alr ln a
basement usua~y ls quite stl~ and usually remains
unchanqed for long perlods. These are conditions which are
not conducive to the di~slpation of smell~. The quantlty of
an obnoxlous gas whlch, lf a~owed to leak into the
basement, would be detected by the human nose, ls quite
tiny. A concentration of gas that would be quite
imperceptible if a~owed to escape into the open air, can
lead to obnoxious sme~s if allowed to e~cape into a
ba~ement.
Basement floors are genera~y made from concrete, and
ordinary concrete, belng ~llghtly porous, i~ lnadequate to
prevent gases in the ground from percolating through lnto
the basement alr. In any case, basement floors usua~y
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develop ha~rline cracks, through which gases can seep.
When gases are present in the ground, the gases o~ten
develop a pressure against the floor and wa~s of the
basement, and this pressure can cause tiny movements in the
concrete, which can cause cracks to develop, and which can
open up any cracks that are already present.
The inventlon lies ln providing a quantity of gas-co~ecting
tubes, and in insertlng the tubes into the undercore beneath
the basement floor. A manifold is coupled to the co~ection
tubes, and conducts the gases away. The gases may be vented
through a stack, or led away in some other suitable rnanner.
One of the benefit~, when the system of the lnventlon ls
used, is that the various plpes and tubes are physica~y
supported very well, by each other and by the basement wa~s
and footings. Thls support is needed because lf the pipes
and tubes were a~owed to shift and move, leaks might
develop~ which would be difficult to locate and expensive to
cure. The system of the invention uses the wa~s of the
basement, and the layout of the tubes, to ensure that each
element of the system is supported securely and firmly and
wlthout strain. In the invention, this security is achieved
without the need for an exceptional level of care and ski~
on the part of the people who insta~ the system.
In the lnventlon, the wa~s and floor of the basement may be
1302~45
g
~ealed wlth a sultable rubber sealant.
In the lnvention, it is necessary that a suitable drainage
n)eans be provided to prevent water entering the co~ection
tubes and manlfold. The co~ecting tubes must not be
a~owed to fill up wlth water, as this would impalr thelr
efflclency ln co~ectlng the ga~es. (The drainage system
need not be perfect however, since it would not be too
damaglnq lf the smells were to reappear temporarily after
heavy rain, providing the smells quickly subsided again.)
If the ground around the buildlnq ls well enough drained
that the water table always lies we~ below the basement
flGor, it may be po~sible, in the invention, to avold addlng
a new dralnage system for the co~ecting tubes. Some
bulldings already lnclude a dralnage system for conducting
rainwater away from the basement wa~s, and if so it wi~
sometlmes be possible for thls already existlng system to be
arranged also to draln the co~ectlng tubes.
The problem wlth whlch the inventlon ls concerned is with
obnoxlous gases that accumulate ln the undercore beneath the
basement of a building. The inventlon makes lt po~sible to
gain access to the undercore, and to relieve gas pressure in
the undercore, wlthout the need to excavate below the
footings. A sme~s-relief system that requlred excavating
below the ~ootings would simply be too expenslve to be
considered.
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In the lnvention, the amount of space that has to be created
(by excavation~ to provide room to install the co~ecting
tubes is hardly more than the ~pace that is required in any
event for the fairly common operation of applying sealant to
the outslde of basement wa~s.
e~ iR-tlon--of~ ~referred Embodiments
By way of further description of the invention, examples of
actual smell-relief systems wi~ now be descr~ed, with
reference to the accompanying drawings, in which:-
Fig 1 is a plan vlew of a basement of a buSldlng, ln whlch asystem constructed ln accordance with the lnvention has been
lnsta~ed;
Fig 2 is a cross-sectlon on line 2-2 of Fig l;
Fig 3 ls a cros~-section, correspondlng to that of Flg 2, of
another system which embodies the lnvention;
Fiq 9 ls a pictorlal vlew of some of the components of the
system of Fig 3;
Flg 5 ls a cro~s-sectlon, correspondlng to that of Flg 2, of
a further ~ystem whlch embodles the lnventlon.
i302i45
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Figs 1 and 2 show an example of an apartment bu~ding, of
plaln rectangular outllne. The particular buildlng shown is
dlvided lnto 4 unlts, and has a floor area of about 25
metres by 10 metre~.
The manner of con~tructlon of the basement of the buildlng
ls conventional, as wi~ now be described. First, following
excavation of the site, concrete footings 1 are laid around
the proposed perimeter of the building, and in line with the
proposed divisions between the units. Next, the supporting
walls of the building are laid upon the footings. The
footings 1 are somewhat wlder than the wa~s, so that lnslde
and ouside ledges 2,3 are formed at the foot of the basement
walls 4.
An undercore S of gravel is laid on the floor of the
excavated hole. Then, a layer of concrete 6 is la~d on the
gravel. This layer constitutes the floor of the basement.
The level of the gravel 5 is set ~o that the edges 7 of the
floor 6 rest on the inside ledge 2 formed by the footing 1.
The problem with which the invention is concerned is that of
gases which may co~ect in the gravel undercore 5, and may
penetrate through the concrete floor 6. There is a
potentlal leakpath between the edge 7 of the floor, and the
correspondlng section of the wall 4. Also, gases may ~eep
through any sma~ cracks in the concrete. Furthermore the
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concrete itself is not completely impermeable to gases.
It can happen that the gases in the undercore 5 bulld up
enouqh pressure to force their way through cracks. Even lf
there is no appreciable pressure bu~d-up in the gas, enough
of a pressure differential can arise, by the mere action of
opening the basement door, for example, to draw enough of
the gases in, by suction, over a period of t~me, through the
concrete.
The procedure for insta~ing the system of the invention
wlll now be described. First, soil is removed a~ round the
building, deep enough to expose the outside ledge 3 of the
footing~ 1, and wlde enough that a man can stand and work ln
the excavation. Unfortunately, lt ls often necessary to
carry out such excavatlon using only hand tools, slnce
powered excavators might cause damage to drains or other
bur~ed services.
The second stage is to dri~ a series of holes 8 through the
footing 1, starting at the crook of the ~unctlon between the
outside ledge 3 and the foot of the wa~ 4. The holes 8 are
angled downwards, and pass rlght through the footlng and
into the gravel undercore 5 beneath the floor 6.
Into the hole~ 8 are inserted respectlve gas-co~ectlon
tubes 9. The tubes are made of PVC and are provided wlth
many ~lot~ 10, ln the portlon of the tube that lles wlthln
1302 14S
the gravel underco~e 5, to allow ga~ to en~er freely lnto
the tube. The tubes 9 are suitably spaced, for example
every one and a half or every two metres. The tubes should
be long enough to reach we~ towards the centre of the floor
6.
The diameters of the holes 8 and tubes 9 should be such that
the tube ls a slldlng flt in the hole. The fit should be
such that the tube is firmly located and physica~y
supported by the hole. The tube 9 may be sealed into the
hole 8 with a suitable adhesive/sealant.
The tube 9 i5 provided with holes, to allow the gases to
enter the tubes. As shown, the gas-entry holes are in the
form of 3aw-cuts formed chorda~y in the material of the
tube, alternately top and bottom, and 3 or 4 cm apart, the
tube being 3 or 4 cm in diameter.
The tube 9 may be in sections which fix together as the tube
is inserted through the hole 8. This a~ows the space that
needs to be excavated in order to insta~ the tubes to be
kept to a minimum.
The outer end~ of the tubes 9 protrude out of the holes 8,
and are fltted wlth sultable tee-pieces ~. ~engths 12 of
PVC tubing run between the tees 11, thus creating a manifold
13. The manifold tublng 13 lies close to the outer ledge 3
of the footing 1, so that the manifold is well-supported.
1302145
g
It can be seen from the drawings that the tubes ~ and the
manifold 13 each provide good lateral support and location
for the other.
The good support is necessary, in order to ensure that the
various pipes and tubes are not dislodged or dama~ed when
the excavation is belng filled in, and in case the fi~ed-in
materlal should later settle. In this connection, the real
problem is that it is not possible to determine at the time
that such damage has taken place, and because to re-excavate
to find the damage, and correct it, is very expensive. It
ls recognised that it would be worth taking quite expensive
steps in order to ensure that the pipes and tubes could not
be damaged: lt ls recognlsed in the lnventlon that the
amount of physlcal support glven to the components of the
system, lnherently in the system of the lnvention, is enough
that special, extra, components for protection and support
during filling-in are not needed.
Before the excavation ls fi~ed in, ie whilst the outer
suraces 14 of the basement wa~s 9 are uncovered, it ls
advisable to take the opportunity to fill in any cracks in
the wa~s, and to apply sealant 15 to the surfaces 14. In
fact, lt wi~ usua~y be economically prudent to seal the
surfaces 14 even if the need for doing so has not been
flrmly determlned. It would be extremely uneconomlcal to
have to re-excavate, in order to apply sealant later, if and
when lt i~ found that sme~s are stl~ seeping through the
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-- 10 --
wa~s.
The purpose of sealing the outer surfaces 14 is to prevent
gases seeplng through the basement wa~s 4. It is of course
well-known to apply sealant to the outer surfaces of
ba~ement walls for the purpose of preventing leaks of water
through the walls. In the lnventlon, the purpose of the
sealant ls more rlgorous, le to hermetica~y seal the
basement walls. To achieve this, the coating 15 should be
thlcker, and should cover more completely the whole outer
surface of the wa~s, than would norma~y be the case ln
water-leak sealing. Apart from those dlfference, the
sealing of the outer surfaces may be conventlonal, and wl~
not be descrlbed further.
It is necessary to ensure that the gravel undercore 5 is
we~ drained. If water were to be present ln the undercore,
the water would enter the collectlng tubes 9, through the
gas-co~ectlng slots 10, whlch would prevent the gas from
enterlng the tubes, and thus defeat the purpose of
lnstalling the system of the lnventlon. In some bullding~,
however, the land is so well drained that no separate
dralnage sytem need be installed to keep the tubes 9 free of
water. However, lt is advlsable to carry out thorough
testlng of the level of the water table, and preferably at
different tlmes of year, before decldlng that extra drainage
ls not requlred: again, it would be most uneconomical to
re-excavate to install extra drainage later.
1302i4S
When all the work below ground level is complete, the
excavated soil is replaced, and re-landscaped as required.
It wl~ be noted that the installed tubes 9 and manlfold 13,
being firmly located, are most resistant to being damaged or
dlslodged during the filling operation, even if the
operation is carried out without less than the usual care.
This i5 important because of the problem that would be
incurred later of determining that damage has in fact
occurred, and the expense that would be incurred of finding,
and then correcting, the damage.
It ls ~ometlme~ advi~able to fi~ in the excavation, not
with the soil that was excavated, but with an aggregate of
pebble~ and gravel. ~hi~ may be done either to aid the
drainage system, or to prevent a build-up of gas pressure
around the footings. It is also advisable, when using
pebbles and gravel, to apply a barrier between the soil and
the flller aggregate. For this purpose, the barrier may
comprise plece~ of polythene sheetlng, which are applied to
the exposed surface of the soil, prior to refilllng. Such a
barrler acts as a molsture barrier, and to keep the soil
from seeplng in and clogging the aggregate.
As mentloned, lt ls advisable to apply sealant 15 to the
outer surfaces 14 of the basement wa~s. It is sometimes
advisable also to seal the basement floor 6. It is
preferred, ln the lnventlon, to ~eal the concrete floor ln
- 1302i~
the fo~owlng manner. Flr~t, the floor 1~ cleared of a~
articles resting on the floor. (This may include such items
as the heating furnace, and can itself be an expensive
operatlon.? Then a rubberised sealant 19 is poured onto the
floor 6 and left to cure. Alternatively, the sealant 19 may
be ln the form of a mat, whlch ls glued down to the concrete
of the floor: in this case, the mat should be large enough
that the edges of the mat extend a few cent~metres up the
inside of the basement wa~s 4.
Once the sealant, whether in mat form or ln poured-on form,
has been set in place on the floor 6, a further layer of
concrete 20 should be applled over the sealant 19. This
layer will form a dummy floor, and lts purpose is to protect
the sealant 19. The layer of concrete should be thick
enough to protect the sealant not only against wear, but
agalnst being penetrated, even if, for example, a hole ls
drl~ed in the concrete of the dummy floor 20. In thls
connection, lt should be noted that it is genera~y not
possible to guarantee to lnform a~ future occupants of a
bullding that there are reasons why the basement floor
should not be penetrated.
The building may include a drainage ~ump (not shown) set in
the basement floor, for co~ecting any water that may
accumulate in the basement, and to some extent in the
undercore. It is conventlonal that such a sump be provlded
wlth an automatically operated pump, which empties the water
~302145
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from the sump. When such a sump ls present, lt is usua~y
advisabler lf and when, in the invention, the basement floor
is to be sealed and extra drainage insta~ed, that the sump
be fi~ed in with aggregate and concrete, and the floor
sealant laid over the fi~ed-in sump. If the sump were left
open, it might be possible for the sme~s to find their way
into the basement through the sump.
It may be noted that it is not so important, economica~y,
fo~ the work of sealing of the basement floor to be carried
out at the same time as the work that requires the soil to
be excavated around the basement wa~s. It can be arranged
that the basement floor be left unsealed for a time, and
only sealed lf in fact the smells are stl~ percelved.
The possible need, in the invention, for extra drainage has
been mentloned. The components however must be lntegrated
into a coherent whole system, and the constructlon of
various combined drainage and venting systems will now be
descrlbed. The important parameters in designing the ~ystem
are the lie of the land, and the severity of the s~ells.
In Fig 2, the manifold 13 was enclosed, and the gases were
led away. In Figs 3 and 4, the manifold 21 ls provided wlth
slots or perforations 22, and the gases are a~owed to
dlss~pate up through the backfi~ aggregate. As shown, a
secondary pipe 23 may be provided, which runs para~el to
the manlfold 21, and lt too 1~ perforated, to increase the
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area of dl~lpatlon of the gas. The secondary plpe 23 may
be set on a slight slope, and may be connected to a sump
~not shown) so that the secondary pipe doubles as a drain
plpe to convey water away.
In Flg 3, the outer ~urface 14 of the wa~ 4 ls coated wlth
~ealant 15, and a barrier 24 of plastic sheeting separates
the backfi~ agqregate 25 from the surrounding soll 26.
In Flg 5, there is no drainage assistance from the lie of
the land, and no convenient main drain to receive the
run-off. Also, the sme~s problem ls such that the gases
cannot be a~owed to escape at ground level.
In Fig 5, the manifold 27 is enclosed, and connected to a
stack. The drain pipe 29 is perforated, and water may weep
into the drain pipe. The drain pipe 29 should be at a low
enough level that water is led away from the footing 1, and
from the undercore 5. The drain pipe 29 connects, via a
connecting pipe 30, to a sump 31. (Depending on the size of
the bullding and the lie of the land, more than one sump 31
might be needed per building.) The sump 31 includes a
soakaway 32. The sump may be fitted with an electric pump
33, which may be arranged to discharge water, through a
discharge outlet 34, lnto the storm sewers.
In the system of Fig 5, it is possible for the obnoxious
gases to seep into, and co~ect in, the sump 31. For this
~30214S
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reason, the sump is provided with an airtight cover 35, and
is provlded with a vent pipe 36 which conducts the gases up
to the roof of the building, to be exhausted.
It has been described that the co~ected gases can be
exhausted through a stack. Alternatively, the collected
gases can be piped away, for exhaustion at a remote polnt:
the gases might even be burnt.
It should be noted that the types and quantities of gases
with which the invention i5 concerned are not poisonous or
corroslve, or dangerous in any way: it is recognised in the
invention that the (expensive) degree of reliability that
would be, and is, needed for dealing with dangerous gases is
not needed when deallng merely wlth unpleasant sme~s.
