Roofing queries
Replacing rotten fascia boards
I recently noticed a gap between my fascia boards and the house. Upon closer inspection, I realised that some of the wood had rotted, causing the fascia to pull away. Is there a way to fix the rotten wood problem other than putting in a new piece of brandering and securing it to the back of the old trusses? The reason I ask is because the damage is pretty close to the wall, making replacement difficult. Is there a better alternative to fascia board, maybe something lighter?
Gideon, by email
Sharl Bennie, our building expert, replies: This is a common problem and what I prefer to do is replace the fascia boards with barge board. The reason for this is that barge board folds over the roof tiles or sheeting and offers a bit of protection to the supporting timber. With flat fascia boards, rain falls directly onto the timber, speeding up deterioration.
Builders often place a strip of brandering along the edges of sprockets that stick out and nail the fascia to the brandering. Firstly, I do not use nails at all if I can avoid it, so I recommend that you start by removing this edge brandering if present.
If the sprockets have rotted badly, cut them back and add new extensions. This can be done by overlapping the new sprocket timber on the high side of the existing sprockets. Make the overlap at least 500mm long for strength.
Get hold of 114 x 38mm rafter timber and if it is not treated I would use a creosote or similar product. Take this rafter and place it under the sprockets and screw through the sprockets into the flat side of the rafter timber. Put a screw through each sprocket and make sure the edge of the rafter lines up with the edge of the roof.
With the rafter securely fitted to the underside of the sprockets, you can then attach the barge board, or the fascia board, to the edge of the rafter timber. Again I suggest that you use screws for this.
This gives a neat finish and I have yet to go back and do a repair on a project that I have fixed in this manner. I wish you the best of luck with your project.
For more information, contact Sharl on 082-554-1921
Roof discolouration
I have recently moved into my house and found that the roof tiles seem to have white discolouration in places. What is this and how do I remove it?
Kyle Danielson, Edenvale
Willem Grove from Coverland/Monier explains:
Efflorescence, often referred to as ‘lime bloom’, is a natural phenomenon and is found in products containing cement.
It is a white deposit that appears on the surface of all concrete based products, and can be unsightly whilst it lasts. Efflorescence is a temporary condition and does not affect the functional properties of the product. Efflorescence is a nuisance not only to manufacturers of concrete products, but also to those involved in their specification and usage. Wind and rain will gradually remove the deposit and the true colour of the tile will be restored
Causes of efflorescence
Concrete consists of sand, gravel, cement and water – with the cement being produced by burning alumina and lime together with other elements. Water in the form of rain, condensation or dew dissolves part of the lime. A barely soluble white film of lime is created by this chemical reaction and is seen on the surface of the tile when the water evaporates.
How is efflorescence removed?
The natural process of weathering (e.g. rain water washing over the tiles) will wash the chalky deposit away and the true colour of the tile will be restored.
Can efflorescence be removed artificially?
A diluted acid mix can be applied as a short-term measure. It is, however, the recommended and accepted practice to allow nature to remove the deposit.
Can efflorescence reappear?
In some instances, efflorescence may recur temporarily. Since the lime content of any concrete product can vary and the weather conditions can also differ, the level of the lime deposit on the surface can also fluctuate considerably. Efflorescence is a natural phenomenon and a temporary condition only.
Can efflorescence be prevented?
Monier Roofing is constantly running tests with various manufacturing processes and weathering systems in order to reduce the likelihood of efflorescence occurring. However, at present, there is no economically viable method for reliably preventing efflorescence.
For further information contact Willem Grove on 011-222-7300
Sealant for gutters
I recently bought a house where the previous owner did a very bad job of installing the gutters. There is only one downpipe on a 16m length etc. When joining the gutters and putting downpiper in, what is the best product to use to seal tehm?
Brett van Rooyen, Centurion
Grant Batty from a.b.e Technical replies:
We recommend that the joint be sealed on the inside with a.b.e Super Laykold Tape, which is self-adhesive (as long as the substrate has been cleaned) and has an aluminium layer on the surface that is UV stable. This can also be used on the inside of the joint where the downpipe intersects the gutter as the a.b.e Super Laykold Tape can be easily cut to the required shape with a Stanley knife or a pair of scissors. If there is a need to seal a joint in a downpipe, a.b.e butyl strip can be inserted into the pipe before the join is made. Remember to clean off the excess product that may protrude from the joint as it is not UV stable, or paintable.
For further information, call the a.b.e Technical Help Desk on 011-306-9000
Galvanised iron roof painting
I would like to enquire whether gloss enamel paint would not last much longer on a tin roof? I recall I had to paint my parents’ house roof in the ‘70's with enamel paint and it lasted many years. Will you please enquire from paint manufacturers if it is viable?
Stefan Greyvensteyn, by email
Toni Stella, our paint expert, replies:
In the ‘70’s, solvent-based paint was the preferred product for painting metal roofs. The danger with some of these paints was the lead content which is very hazardous and white spirits which evaporate into the air as volatile organic compounds (VOC’s) causing pollution.
The environmental constraints have forced better technology than ever before, and now water-based roof paints are more varied and outstanding than 10 years ago. A good quality acrylic roof coating has far better gloss retention and fade resistance than oil-based paint.
It is worth bearing in mind that on exteriors where paints are exposed to severe UV intensity, heat and cold conditions, these will cause the metal to expand and contract, resulting in cracking and flaking of the paints.
Water-based acrylics will also adhere well to the old weathered oil-based paint, after degreasing it with an alkali cleaner using a scouring pad to abrade the surface to allow better adhesion. Always rinse off with clean running water. Make sure paint can dry for at least seven days before rain is expected.
Important!
* Always apply two coats of paint at 6-7m², allowing 4-6 hours drying between coats.
* Rusty areas must be primed with two coats of an anti corrosive primer (water-based).
* Estimate paint quantities by measuring the floor area and add approximately 20% for the profile, an additional 20% for the pitch, and divide this area by 6m²/lt.
For more information, contact Toni on 082-781-9669.
Cement roof problem
I have a flat concrete roof in my house. There are two areas where water leaks through the slab. While I know I have to sort the problem out with my waterproofing contractor, I am concerned about the white deposit that has developed below where the water comes through. What is this material and is it a sign of a problem?
The Cement & Concrete Institute’s Information Centre replies:
The white deposit you refer to is the same material that stalagmites and stalactites consist of, namely calcium carbonate.
Calcium hydroxide that is present in hardened concrete is soluble in water and, as water moves through the concrete, it will dissolve calcium hydroxide and carry it with it.
When it emerges from the bottom of the concrete slab, much of the water will evaporate, leaving behind calcium hydroxide, which will combine with atmospheric carbon dioxide to form calcium carbonate. The deposit is therefore nothing to be concerned about and once the roof is properly sealed, no further deposits should form.
Removal of the deposits is fairly simple; physical chipping and scraping should remove most of the deposit and the remainder can be removed using a 10% solution of phosphoric acid or proprietary mortar remover in water. Wash the area thoroughly with tap water after treatment. Reinstatement of the paint should be easy once the deposit is removed.
Direct your concrete queries to the Cement & Concrete Institute’s Information Centre on 011-315-0300 or email info@cnci.org.za
PVC ceilings
In your last issue, you showed pictures of PVC ceilings (pine and mahogany) that look just like the old knotty pine interlocking planks of yesteryear. Where can I buy these panels?
Danie Potgieter, by email
Ed replies:
Yes, they do resemble knotty pine and are available in various colours, including white, are maintenance free and require no painting! These PVC ceiling panels are manufactured by Southern Profiles and available countrywide.
Contact Paul Gallant on 082-577-2520 or 021-949-5803 or email paul@southernprofiles.co.za for your nearest supplier.
