18 May 2020

Storm Desmond and damp wall misery

Storm Desmond and damp wall misery

As the full effects of storm Desmond are felt across the U.K and especially in Cumbria and the Scottish borders, for many families the clean up cannot even begin until the floodwater subsides.   Being based in Cumbria ourselves, we wish everybody affected by the storm well as the county tries to recover once again from severe flooding.   The factory is open today and limited orders are being despatched although our carriers have advised that there will be no “next day” service due to the number of road closures and power cuts.

Even those lucky enough not have been flooded are not without their problems.  The gale force winds and exceptional rainfall have resulted in a spate of structural damage, lost roof tiles and moisture ingress through rain soaked walls.

In fact since the rain started falling in earnest over two weeks ago, Kingfisher has seen a dramatic rise in enquiries about how to stop rain driven dampness.

We therefore thought it might be useful to prepare a check-list of general advice on dealing with rain soaked walls and damp problems.

1.  Floodwater

Even if your home is not actually submerged, flooding in the surrounding area affects the water table beneath your home and can introduce water pressure under walls that might not normally suffer from damp.    In normal circumstances rising damp occurs very slowly but if there is water pressure from a rising water table, this process is accelerated, especially with cavity walls and soft brick or stonework.   Look for “tide lines” from skirting board level upwards.

Advice:  This will be beyond the compass of most DIYers and specialist advice should be sought as the walls may require tanking.   Move all furniture away from the affected wall to allow air to circulate which in turn will help with drying out.  If there are any plug sockets or light switches in the vicinity, isolate the relevant breaker at your main fuse board and seek advice from a qualified electrician.

2.  Window and Door Frames

Window cills and lintels above windows often present a partially flat surface for rainwater to gather upon and it is this accumulation of water which creates a weak point for water ingress, through pointing cracks or porous masonry.  Perimeter pointing of window frames and doors with mastics/ sealants, is another area of weakness as sealants can degrade over time allowing water to penetrate.  Both of these problems commonly result in damp patches appearing under window ledges and above window reveals or around curtain tracks.

Advice:  Check for “soft” mortar and / or cracks in the mortar joints around cills and lintels. Rake out loose mortar back to sound substrate and re-point with a repair mortar incorporating some “Kingfisher Pointing Solution” for improved waterproofing, flexibility and durability.   Similarly with the perimeter window frame mastic, remove any decayed selant and re-seal with Kingfisher “1 for all” hybrid polymer sealant.  “Kingfisher 1 for All” bonds even to damp surfaces where silicone won’t adhere.  If the walls are bare stone or brickwork, also treat the area with “Kingfisher Storm Seal” water repellent, even if the masonry is still damp.  If the walls are painted consider re-coating with a premium grade masonry paint (such as Kingfisher Weatherflex) as soon as weather conditions permit.

3.  Porous Masonry

If there are no obvious cracks in the masonry or around the windows etc. then the problem is most likely that of porosity.  This arises when water finds enough micro-pathways in the brick, stone or mortar to fully saturate the wall in one or more locations.  This can happen for a number of reasons including soft brickwork, frost damage, defective mortar joints, weak stone etc.  Commonly there is one elevation, often a gable end which takes the brunt of prevailing weather.  Constant soaking over days and weeks mimics full immersion so that moisture is continually fed into the substrate,eventually finding its way through to the internal walls where it shows up as a damp patch or patches. 

Advice:  Treat the affected elevation by spraying it with a “wet apply” waterseal such as “Kingfisher Storm Seal”.  This is relatively easy to apply with a low pressure garden sprayer and must be applied to a damp surface to achieve maximum efficiency.  “Storm Seal” is easy to apply and unlike traditional formulations CAN be applied in damp conditions so you don’t need to wait for a perfectly dry day to apply it.  If the wall is painted you should consider re-painting the entire elevation with a premium masonry paint (e.g. Kingfisher Weatherflex) as soon as weather conditions permit.

4.   Chimney Leaks

Chimneys whether “in use” or “decommissioned” are a common failure point for water ingress for various reasons.  Chimneys stacks are at the highest point on a house and consequently are more exposed to bad weather.  Chimney’s are subject to rapid swings in temperature, depending on whether a fire is burning in the hearth or not, so thermal cracks are inevitable.   Decommisioned chimneys are often capped with cement to stop rainwater ingress but over time such caps decay and leaks are common.

Advice:  Check for “soft” mortar and / or cracks in the mortar joints on the chimney breast and stack. Rake out loose mortar back to sound substrate and re-point with a repair mortar incorporating some “Kingfisher Pointing Solution” for improved waterproofing, flexibility and durability.   Use the same repair mix with a little fine aggregate to replace a leaking “cap”.     Treat the entire stack and chimney breast area with “Storm Seal” or repaint with “Weatherflex” in the case of painted render, brick or stonework.

5.  Cavity wall insulation

Another common origin for penetrating dampness is unfortunately “cavity wall insulation” which has been injected or “blown” into cavity walls to improve energy efficeincy.  Although this insulating material is supposed to be non-absobent, in numerous houses it has acted as a conduit for moisture to migrate from the outer wall to the inner wall.

Advice:  You can remove the cavity wall insulation but this involves drilling core holes and is relatively invasive.  Before going to that extent, we recommend that you first try the less costly repairs outlined in 2 and 3 above to fully waterproof the outer leaf so that moisture is not getting into the cavity in the first place.    Once cavity wall insulation is wet it may take some months to dry out so ear this in mind when assessing whether or not your repair strategy is working!

The foregoing list is obviously not exhaustive so if you need further advice, please call our technical help team on 01229 869 100 and we will be pleased to advise you.  It also helps us greatly to have a picture of the problem so take a photograph of the problem and attach it to the enquiry form in the “contact us” section of the Kingfisher website.