Regulations for thatch roofs
Thatch roof regulations for thatch lapas, thatch houses and modern thatched houses
THATCH ROOF CONSTRUCTION LAWS
FIDDLER™ ROOFING PRODUCTS have seen the need to provide homeowners with all the relevant thatch roof regulations. Home owners and thatch roof contractors are advised to familiar themselves with these regulations.
FIDDLER™ ROOFING PRODUCTS makes SANS 10407, freely available to the general public. SANS 10407 relates to the construction of thatched roofs in South Africa.
Click on the button below to view the SANS 10407 regulation.
The Thatchers Association of South Africa provided FIDDLER™ ROOFING PRODUCTS with the following information. We make it available here to the general public.
MUNICIPAL BY LAWS REGARDING THATCH ROOFS
Due to the nature of urban area’s being substantially more built up than a few years ago, the municipality is now forced to ensure that all households are safe. The primary concern is against fire. Unfortunately thatch roofs are major fire risk, not just for it’s owner but for the surrounding areas too.
Lapa’s and thatchroofs are now governed by the same laws that govern conventional buildings. ( South African National Standards SANS ) The local councils will therefore by conducting an inquiry into illegal buildings, thatchroofs as well as lapa’s. Aerial photographs will be taken to identify where such structures are situated, the council will then target the above mentioned structures.
Owners of the premises where buildings, thatchroofs or lapa’s are:
a) not built to standard or not within the specification set out in the SANS or,
b) where approved plans was not given by the council,
c) no rational design or engineers certificate, will be issued with notices relating to the misdemeanor and have to apply for approved plans and have engineers certificates issued as well as a certificate of rational design. Please allow us, Die Grashut the opportunity to inspect your thatch roof / lapa to ascertain whether or not it is built to standard.
INSURERS SET HIGH STANDARDS FOR LAPAS
Lapas are ideal home enhancements, but few people are aware of the high standards set by insurers that need to be complied with. Article by Dirk Benadé, Manager of Conamore Insurance Brokers.
The special ambience that makes a lapa so unique often prompts home owners to build one of their own to create a space in which they can entertain friends and family. Very few people are however aware of the high standards these lapas have to comply with. The standards are enforced by a variety of entities, including your local municipality, the insurers and – if you live in a sectional title complex – the trustees and body corporate. Article by Dirk Benadé, Manager of Conamore Insurance Brokers.
If you stay in a sectional title complex, your fenced garden area is registered as common property but you are granted exclusive use. Because of this and the fact that a lapa is regarded as a structure by the National Building Regulations enforced by your local municipality, you need to obtain permission from the following entities before you start building:
• You need to hand in a plan of the lapa at the local authority. If your lapa exceeds the prescribed building line, you need to obtain permission from them for a relaxation of the building line.
• As stipulated in the Sectional Title Act (Act 95 of 1986) the body corporate of your complex will need to approve the building of the lapa.
If you fail to obtain permission from the above entities they have legal grounds to force you to take the lapa down at your own cost.
Insuring the lapa
The insurance companies classify a lapa as a non-standard structure. They therefore regard it as a special risk structure and special rates are applied to calculate premiums.
The insurers furthermore require that any capital addition to the original building should be disclosed to them, whether you insure it or not. The risk of not disclosing it is that in the event of a claim the insurer can value the unit as under-insured. Consequently the insurer will apply an average to the claimed amount and scale the claim down proportionately.
It is important to note that it is not only the thatch structure that should be insured. The insured value should include any fixed (non removable) structures / appliances fitted underneath the lapa, including the floors, braai, bar etc.
The value at which the lapa should be insured is the total replacement cost to repair / replace the lapa in the event of damage or total loss by one of the perils for which the policy provides cover for example wind, storm hail, fire etc.
The National Building Regulations furthermore determine that a lapa with a size of less than 20m² should be at least 1m from any other built structure. If the boundary wall is fitted with an electric fence the same distance applies
If the lapa is more than 20m² in size it should be at least 4 meters from any built structure and 1m from the electric fence. If you fail to comply with these standards the insurer will apply normal thatch rates to any building that is affected by your lapa, in order to calculate the insurance premium. This means that you might find yourself paying the premium for a thatch roof house instead of a normal tiled roof.
When you compile a building plan of the thatch lapa, remember that you have to take into account the unit on the other side of the wall and in some cases it could be a number of units attached to each other. This will all depend on the position of the lapa and whether the necessary fire walls are in place. If the lapa is attached to a building (for example over the patio), the insurer will apply thatch rates to such building regardless of the size of the lapa. This could mean that if the insurer is of the opinion that your lapa is a fire risk to your unit as well as your neighbour’s, you will be liable for the additional premium on your unit as well as the neighbouring unit / building.
Special fire precaution
The insurers prescribe that the following measures be taken in order to protect a lapa against fire:
• In cases where a chimney penetrates the roof of any thatch structure, it should be constructed in such a way that the exterior in contact with the thatch cannot become hot. In normal chimneys a full brick thickness (220 mm) is necessary to satisfy this requirement.
• All mortar joints in the stack must be properly filled.
• Dress the area where the chimney stack penetrates the roof plane with sheet metal or fibreglass reinforced polyester flashing over and underneath the top surface as well as between the layers of the thatch. The width of the flashing should be at least 250mm.
• The chimney should be 1m higher than the thatch roof.
• A spark arrestor, fitted not less than 700mm from the top of the stack must be provided in all chimney stacks. The typical spark arrestor comprises of a 10 x 10 mm (minimum) section of stainless steel wire mesh across the full width of the flue and securely built into the flue around the edges or supported on mild steel dowels.
• Have the chimney flues cleaned at least once a year to avoid an accumulation of soot which can ignite or generate sparks.
• Keep an area of up to 25m around the lapa / thatch clear of unkept plants, grass and weeds to prevent fire hazards from sparks, etc. This condition however does not apply to cultivated and maintained lawns and gardens.
• Have fire fighting equipment ready on site. In compliance with the National Building Regulation 12, you are responsible for the testing and servicing of the equipment once a year to ensure that it would be ready for use at all times. In most cases a 4 kg dry powder fire extinguisher should be sufficient.
• It might be a good preventative measure to use treated grass for the thatch but it is not compulsory.
Although a lightning conductor is not compulsory, the insurer may insist on the installation, and it might be a good preventative measure, especially in Gauteng with its frequent thunder storms. According to the insurers an effective lightning mast is of such a height as to provide a shielding angle to the structure/s it is meant to protect. A minimum angle of 45 degrees taken from the highest tip of the mast to ground zero is prescribed. The mast can either be attached to the building or free-standing and should furthermore be bonded to the earth electrode of the structure or an earth electrode of its own.
The metals that were used in the thatch construction (i.e. wire mesh, metal coated insulation, etc.) should also be bonded to the earth metal water main or earth electrode of the structure. If the chimney or gable ends extend above the shielding angle of the lightning mast, a peripheral conductor should be used around the chimney or along the gable. This should be connected to a down conductor bonded to the earth electrode or water main.
If you would like to know more about insuring a lapa please contact Conamore Insurance Brokers (CIB)
LAPA CONSTRUCTION - ALL YOU NEED TO KNOW
Thatch should have a minimum thickness of 175 mm and a maximum thickness of around 250 mm and the thatch should be well-compacted. Good compaction of the thatch results in better durability and will also slow down the spread of fire.
A thatch roof should have a minimum pitch of 45°. The steep slope is needed so that water will run off from the roof surface with minimum penetration into the thatch.. At a pitch of less than 45° the thatch will decay and leak much sooner.
Thatch roofs require regular inspections by an experienced thatcher every 8-10 years. Re-dressing of the thatch roof (removal of rotten thatch and the addition of a new layer) is usually necessary on a 15-20 year cycle. If maintenance is not done and decay is allowed to reach the stage that the twine fixing of the thatch is exposed, then the lifespan of the roof is considerably shortened.
Once the twine fixings are exposed, rainwater will penetrate by running down the stitching twine through the thatch and into the building. Exposure of the twine also causes the twine stitching to rot and results in the deterioration of the entire roof cover – once the stitching goes and the compaction of the thatch bundles is lost.
The rate of loss in thickness of a thatch roof can be reckoned at approximately 20 mm over 7 years. For a 175 mm-thick thatch layer, the thatching twine will be about 80 mm below the top surface. This means that, given normal conditions, the twine will only become exposed after 20 years or so. Maintenance and re-dressing should be carried out well before this point.
During maintenance of a thatch roof, all rotted thatching material should be completely stripped out and the thatch cover well brushed before adding new, tightly packed bundles of thatch grass to the top of the roof. Re-dressing a thatch roof usually adds about 100 mm to the thickness of the roof cover.
Thatch roof design:
The design of a thatch roof should always be as simple as possible. The inherent ability of thatch to adapt to freeform curved roof shapes allows designers to develop less formal roof layouts, than is the case with conventional roof structures.
Because flashings on a thatch roof often result in waterproofing problems, features that penetrate the roof should be avoided wherever possible. Chimney stacks should be placed to penetrate the roof plane at the ridge. Any soil vent pipes are best located on external walls, so that they penetrate the thatch covering only near the eaves line.
Ridges and valleys are also potential weak points in the weatherproofing of a thatch roof. In the design of multiple-level thatch roof structures it is important to prevent a concentration of rainwater discharging from a high-level roof onto a thatch roof at a lower level.
Thatch roof structure:
A thatched roof is a heavy structure and the walls and foundations must be sufficiently strong to carry the load of the roof. Thatch with a thickness of between 175 and 200 mm, weighs between 35 to 50 kg per sq. meter.
In South Africa, the roof structure is usually constructed from treated eucalyptus (blue gum) poles with a minimum diameter of 100 mm. The use of fire retardant treated timber for the roof structure improves the fire safety of the roof. The thatching battens are usually treated eucalyptus poles with a minimum diameter of 25 to 32 mm.
To cope with an anticipated maximum thatch covering thickness of 255 mm attained during the life cycle of the roof, battens should be spaced a maximum of 250 mm apart, except along the eaves and ridges where the spacing between the first 2-3 battens should be 150 mm. Wider batten spacing may cause sagging of both the thatch grass and the battens. To limit batten sagging, rafter poles should be spaced between 750 and 900 mm apart.
All electrical wiring must be inside plastic conduits and should not penetrate the thatch layer. Steel pipes, cables or electric wiring should never be in direct contact with the thatch. Electrical and other services (telephone and TV) should always enter a building at ground level and never be closer than one metre to the thatch.
Lightning conductors should be installed to protect thatched buildings or structures in accordance with the recommendations contained in SABS 03:1985. The installation of lightning protection should be undertaken only by qualified contractors.
An approved fire-retardant coating should be applied to all thatch surfaces, internally and externally, including the underside of roof eaves and roof voids concealed by suspended ceilings. The fire-retardant treatment should be applied according to the manufacturer’s specifications.
Fire-protective membranes (a non-combustible layer beneath the thatch) can be installed to restrict the flow of air and slow the spread of a fire. If, for aesthetic reasons, a thatch finish is required on the underside of the roof, then the barrier layer should be placed on a layer of thatch not more than 6 mm thick.
South African building regulations stipulate that any thatch roof covering a roof-plan area greater than 20 sq. meters must be constructed at least 4.5 m from any boundary. This is to prevent a fire from spreading neighbouring structures. If a thatched lapa has been erected within the safety distance of 4.5 m, then – in common with smaller lapas – further steps must be taken to ensure adequate fire safety.
Thatched lapas with a roof plan area of less than 20 sq. meters are regarded as non-combustible and can be built within one metre of the boundary, provided the following conditions are met:
- The lapa must be a non-habitable structure.
- The lapa must be free-standing and not be attached to any other structure, either on the same premises or on adjacent premises.