from RICS Home Survey reports





Surveyors are only too aware that some of the most serious defects that afflict our homes –   damp, rot and beetle infestation – very often have their root cause in defective guttering and downpipes.  So keeping rainwater fittings in good shape is of fundamental importance to maintaining the health of buildings.


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If  water is allowed to ‘pond’ at the base of walls, over time it can soak into the walls and eventually softened the ground, robbing the property’s foundations of support. So channelling surface water well away from your house is of prime importance.

In older properties this was often achieved simply by running pipes out through the pavement into the street, or into a ‘combined’ drainage system. But today in most districts surface water must, by law, be kept separate from the foul waste drainage system, to avoid overwhelming sewage networks. So unless you’ve got a handy nearby ditch or stream, surface water normally needs to be safely discharged via underground pipes out to a soakaway in the garden. Soakaways are rubble filled pits which should be located at least 5 metres from the house.


Things to check


1/ Leaking downpipes

There are a number of reasons why downpipes leak. They sometimes become blocked and start overflowing at a joint. They may have split or cracked, or might have become dislodged. Cast iron pipes may have rusted through, discharging water straight onto the wall.  If water in a blocked cast iron downpipe freezes it is likely to expand and split the pipe, saturating the wall to which it is fixed. Plastic downpipes can be especially vulnerable to impact damage.

Remedial work:   Blocked downpipes can be cleared, taking care to first cover the gulley below the pipe to stop any debris entering the drainage system. This can be done using a long pole or stiff wire pushed down the pipe to dislodge the blockage.  But where downpipes are connected at their base directly to underground drains (rather than discharging over gulley gratings) access for clearing blockages can be restricted unless connected via a gulley with an integral ‘rodding eye’.

Cracked and broken pipes should be replaced. Brackets are needed at every joint, and no more than 1.8m apart.  Sometimes brackets are fitted with spacers to prevent the pipe contacting the wall, leaving sufficient space for periodic painting to inhibit corrosion. To prevent leaves and silt blocking downpipes, special wire or plastic ‘balloons’ can be fitted in gutter outlets.


2 /    Leaking or overflowing gutters

The most likely cause is simply down to blocked gutters, or more rarely a blocked hopper or downpipe. Other causes include poorly aligned gutters set to an insufficient fall, or localised sagging or damage. Or there simply may not be enough downpipes to efficiently discharge rainwater.  Plastic gutters are jointed using rubberised gaskets which tend to perish over time, so it is not unusual for small leaks to develop at joints. Plastic guttering can also be prone to sagging or twisting due either to old age or lack of support from broken or missing brackets. It is also easily damaged by having ladders leant against it. Water leakage is most serious where it can occur unseen, which is why gutters on Georgian and early Victorian roofs hidden behind parapet walls can be such a concern.

Remedial work:  . Before debris and plant growth completely chokes your gutters it needs to be scooped out with a trowel, a job that can normally be done with ladder access.

Older properties sometimes have hoppers which are particularly prone to blockage and need to be periodically cleared, or replaced if corroded, split or leaking. Cast iron guttering is generally more time consuming to work on. Joints are bolted together but once released joints can be cleaned with a wire brush, before applying rust inhibiting metal paint. Once dry, gutter sealant should be applied to the joint which is bolted back together and reinstated.

With PVC guttering, defective rubber seals or connectors at gutter joints or stop ends can be replaced with new fittings taking care to leave expansion gaps.

Sagging gutters need improved support so there is at least one bracket per metre of guttering. If there is no fascia to secure them, gutters are sometimes held in place with special brackets fixed to the rafter feet. If the brackets are fixed to a timber fascia board, the fascia may have rotted or may not be level, and will first need to be overhauled or replaced.

Any defective lengths of guttering should be released from their clips and replaced. If it’s only one section, it should be possible to obtain a matching replacement, but it’s important to carefully check the shape and diameter. Fitting higher capacity ‘deepflow’ gutters is one way to accommodate a greater volume without overflowing. Also check that roofing underfelt is projecting down into the guttering about 50mm as this helps to minimise the risk of rainwater running down the wall.

If an otherwise well maintained system overflows, the problem may be one of design. In some older properties the number of downpipes is minimal, which could cause overflowing in severe weather. As a rule of thumb, one downpipe should serve no more than three smallish terraced houses (preferably two). The new pipe will need to  discharge at its base by connection to a surface water drainage gulley leading to a soakaway.


3 /   Main walls damp at low level

In most cases this will be down to leaks and overflowing from gutters or downpipes splashing against walls as described above. But damp problems at ground level can also develop where downpipes discharge directly onto the ground next to the house, or where gulleys have become blocked. Over time this can cause the ground to become marshy and unstable, even affecting the support to walls from foundations.

Damp in walls at low level is commonly misdiagnosed as ‘rising damp’, with expensive and unnecessary injection damp treatments carried out at the behest of mortgage lenders, rather than solving the true cause of the problem.

Remedial work:  Where downpipes discharge onto the ground they should be diverted away from the house and connected to an underground surface water drainage system or to a soakaway to prevent flooding of water causing damp to the main walls. If the water from a downpipe is overshooting the gulley and splashing the wall, the pipe can be extended at its base by fitting a ‘shoe’, so that it discharges accurately. But connecting downpipes to water butts is not necessarily a good solution as these often overflow.

Ponding of water around gulleys indicates that the water is not running away properly, often due to a build-up of grease and solid matter in the trap, or a blockage caused by debris. A simple blockage may be solved by removing leaves etc from the gulley grating, or can be cleared with a solution of caustic soda or flushing through with a high pressure hose. Modern gulleys have a fitted ‘back inlet’ to allow rodding.




N.B.  This is by no means an exhaustive list, and much depends on the age and type of property you’re surveying


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