A guide to flat roof maintenance A guide to flat roof maintenance

The importance of good roof maintenance

As a landlord, you have a legal responsibility to keep your tenant's home in a good state of repair and one of the most important checks to make is that the roof is wind and watertight.

If rainwater is allowed to penetrate the property via the roof, not only can it cause extensive damage and negatively impact the value of your investment, but you could be putting your tenant's health and safety at risk and may face fines and further legal action if you fail to make timely and proper repairs.

Read property expert Kate Faulkner's guide to maintaining your flat roof.

How to maintain a flat roof

You should inspect the roof twice a year, whatever your flat roof construction type is. As winter is the season when properties are most likely to suffer damage, it's advisable to make these checks:

  1. At the end of autumn, to ensure the property is wind and watertight ahead of the potentially extreme cold and wet weather.
  2. At the start of spring, checking for any damage sustained over the winter and making necessary repairs as soon as possible.

There are three main roof construction types used on residential properties:

  • shingle (individual overlapping elements)
  • asphalt
  • thatch

Each of these is susceptible to different forms of wear and damage, so needs to be checked in the right way. You may want to engage a professional to make these checks for you, but it's certainly something you should be able to do yourself, with a keen pair of eyes!

How to maintain a shingle roof: slate & tile

The most common type of shingle roof is slate or tile, but the pieces can also be made from wood, flagstone, metal, plastic, and composite materials such as fibre cement, held in place with either copper wire, nails or pegs.

Over time, or as a result of adverse weather, the slate/tile can crack and slip out of place and if they're not fixed quickly, water will get in through the gaps and can damage both roof timbers and plaster ceilings.

The first step is to check the roof from inside, so go into the loft with a torch and make a thorough inspection:

  • Are there any gaps where you can see daylight?
  • Are there any water stains on the roof timbers?
  • Are there any water stains on the inside of the tiles/slates?
  • Can you see any hairline cracks on the tiles/slates?
  • Is there any excessive moss growth?

Importantly, make sure any roof or loft insulation is not blocking ventilation in the eaves, as that could exacerbate any penetrating damp issues and accelerate timber decay.

Outside, you can see a lot from ground level, so there isn't necessarily any need for a ladder. Check:

  • Are any tiles/slates out of line - i.e. slipped?
  • Do tiles look as though they have a powdery surface? (This is a sign that they are deteriorating and need to be replaced.)
  • Are there any gaps in the mortar joints along the ridge at the top?

If there's evidence of damp inside the roof space, be aware that it may not be down to the tiles themselves; leaks often come from failing flashing or guttering issues.

If you do need to go up a ladder, make sure it's well anchored at the bottom and try to avoid resting the top against guttering, as this increases the risk of the ladder slipping as well as potentially causing damage.

How to maintain a flat asphalt roof

Many properties have a flat roof on part of the building, usually where there has been a single-storey extension, and it tends to comprise timbers covered with asphalt. According to the Confederation of Roofing Contractors: "Most domestic flat roofs use two or more built-up layers of bituminous felt as their waterproofing, each comprising a reinforcing base coated with oxidised or modified bitumen."

Assuming the job has been done properly, a flat roof may not need repairing or replacing for 15 years or more, however, it is still advisable to check it twice a year, ideally just after rainfall:

  • Is water pooling anywhere?
  • Are there any bare patches?
  • Is the asphalt cracked anywhere?
  • Are there any blisters or bubbles (caused by the sun's heat)?
  • Are the joints in the roof covering properly sealed?
  • Are the edge trims in good condition?

In addition, leaves and other debris can easily collect on a flat roof - particularly in the corners - and block water drainage outlets, so check it regularly though the autumn and early winter.

If you need to go up a ladder and onto a flat roof, it's advisable to put down temporary boards for safety.

How to maintain a thatched roof: straw

A good thatch shouldn't need regular maintenance and should last around 25 years - possibly less if long straw is used and more if it's combed wheat. Regardless of material, it's likely to need replacing around every 10-15 years.

You should check the thatch for:

  • Rodent damage. Squirrels, rats and mice can devastate a thatch, so check inside the roof space and make sure there are no nests or droppings. You should consult a local pest expert and take advice on deterring rodents.
  • Areas of missing straw/wheat on the outside, which may be due to birds picking it off. A wire mesh over the top will help deter them.
  • Discolouration, which may indicate dampness, paying particular attention to any valleys where rainwater is most likely to collect.
  • Moss growth, which can cause damp and exacerbate decomposition.

To mitigate fire risk with thatched roofs, you should also:

  • Ensure any wiring in the roof is well-sealed and rodent proofed.
  • Keep the loft clear of any combustible materials.
  • Sweep chimneys twice a year.

Other checks to ensure the property is wind & watertight

In addition to checking the main part of the roof, you need to make sure everything adjoining it is also sound:

Flashing - this is the term for the metal pieces (sometimes PVC) that are used to divert water from places where it is most likely to collect or penetrate, such as where a chimney meets the roof, where a flat roof joins a wall and in valleys where two sections of a roof meet. You need to check that the flashing hasn't lifted at the edges or split, as that would let water seep in behind it.

Chimney - as well as the flashing around the bottom, check the chimney stack for cracks and missing mortar between bricks, as that could cause rainwater to penetrate all the way down the chimney breast inside the property.

Guttering & drainage - it's important that you keep the guttering clear and free of debris such as leaves and moss, so that rainwater and melting snow and ice can escape freely. If the guttering becomes blocked, water can back up and be forced underneath the roof covering, penetrating the inner roof space. Make sure the joints are in good condition and there are no splits that could cause rainwater to cascade down the walls of the building itself.

You should also be aware that failing to properly maintain the guttering, downpipes and drains may invalidate any insurance claim you make for related damage to the property.

What to do if your roof is damaged or degraded

If there are signs of damage to the roof construction or penetrating damp but you're not sure exactly what the issue is, then you may want to arrange for a local RICS surveyor or RPSA surveyor to carry out a full inspection.

Alternatively, or if you can already see what the problem is, contact a roofing company to double-check the roof and make necessary repairs.

It's wise to get at least two quotes before engaging anyone to carry out work and you should make sure that they're a member of either The National Federation of Roofing Contractors or the Confederation of Roofing Contractors. Ideally, they should also be a member of one or more of the following:

If it's a flat roof that needs repair or replacement, make sure that all quotes you obtain include provision for:

  • The deck - e.g. plywood or timber board
  • A vapour control layer
  • Insulation
  • Two top layers of waterproofing.

Be aware that if a contractor suggests weatherproofing a flat roof with a rag or fibre-based product, these have now been withdrawn from British Standards and are no longer recommended.

5 checks to make before engaging a roofing contractor:

  1. Do they specialise in your particular type of roof construction?
  2. Have they given you a fixed-cost quote?
  3. Do they have insurance for carrying out works?
  4. Will they give you a written estimate of how long works will take?
  5. Is their work covered under any guarantee/warranty and what would happen to these if the company went bust? Will they survive them?

While a roof is unlikely to need major repairs or replacement more than once during the time you own your buy to let, you should budget properly for the cost of that from the start, to make sure:

  1. You don't get hit by an unexpected bill.
  2. You have sufficient funds set aside to carry out works as soon as they're required.

That way, you can be sure you're protecting both your tenants and the value of your investment.

Damage to the structure of the building you let out, including roof damage, can be covered under Direct Line for Business Landlord Insurance. Read more about the insurance we offer here.

Get more property maintenance tips from Kate Faulkner here.








Landlord Insurance Kate Faulkner
Kate Faulkner

Kate Faulkner
Last Updated: 15 Aug 2016
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