Shednotes15 – On pointing, grouting and gravel

As previously mentioned, one of The Shed’s projects is The Filofacts, a reference work designed for your go-anywhere steam-powered personal organiser.
It is not yet layout-ready, but making it so is a project for the winter months.
Meanwhile, help yourself to the pages filed so far at
https://hack4hire.wordpress.com/category/the-filofacts/
Here are some new entries waiting to be filed, courtesy of Jeff Howell, whose Ask A Builder column in the Telegraph is The Shed’s guess for best-read column in newspapers …

A FILOFACTS ON …. POINTING & GROUTING
In Telegraph of 13.4.14, the paper’s DIY and building consultant, Jeff Howell, was asked his opinion of mechanical re-pointing tools. He commented:
“As with any method of repointing, the main problems are that (a) it is usually unnecessary, and (b) it is often done badly, causing damage to the brickwork.
“The mortar between bricks (for which also read ‘stones’) should be viewed as a sacrificial medium. It should be softer and more breathable than the bricks themselves, allowing movement and the passage of moisture. It is natural for the mortar to weather away over the years, leaving the bricks intact. After perhaps a century or so, re-pointing might be needed.
“Unfortunately many home owners, and some ignorant surveyors, view even minor erosion of the pointing as a defect, and think the wall should be spruced up by raking out and repointing.
“All raking-out will cause some damage to the edges of the adjacent bricks, no matter what tools are used. The joints will become wider, meaning that the re-pointing will take up a larger proportion of the wall’s area and change its appearance. Re-pointed walls often look as if they have been redrawn using a blunt pencil.
“In the event that re-pointing is really necessary, it should be done using a soft lime-and-sand mortar – this is especially important for pre-1939 buildings. If lime-built brickwork is repointed with hard cement-based mortar, the pointing is quite likely to work itself loose within a few years, but not before it has hastened decay of the masonry by cracking, spalling and frost damage.”
Next question was:
“For years I have been filling in the spaces between paving slabs that were put down when the house was built. Overall it is a considerable area. Every year the cement once again breaks up and the spaces are back. What I would envisage would be a sort of large icing bag which one would squeeze and fill in the spaces permanently with a liquid substance. Is there a way?”
Sir Jeff, as he is known in The Shed, replied:
“As with my previous answer, I have to report that the problem lies with the materials, not the tools.
If your paving slabs are bedded on sand, then they will move around in response to all sorts of influences – thermal and moisture expansion/contraction, impact from human traffic, and growth of tree roots. There is no point filling the joints with anything other than sharp sand.
“If the slabs are bedded on concrete or cement-based mortar, you’ll have more of a chance with pointing or grouting. The same principles apply as before – the mortar should be softer than the paving slabs. Try a 6:1:1 mix of sharp sand, cement, and hydrated lime. Rake the joints out fully and brush or vacuum the dust out. Damp-down the joints with a fine spray from a hosepipe, and press the mortar (which should be of a stiff consistency) firmly into them. When the mortar has started to cure (after an hour or two) tool it smooth with a brick jointer or piece of metal pipe. Cover it up to protect it from frost, and in dry weather keep it moist and covered with polythene for a least a week.
“You must accept, though, that exterior paving slabs are constantly exposed to the ravages of the weather, and no matter how well you do the job, it won’t last forever.
* See also the Filofacts entry on cement etc. at
https://hack4hire.wordpress.com/2013/07/15/a-filofacts-on-cement-etc/
* For more Jeff Howell, see http://www.askjeff.co.uk/

A FILOFACTS ON … GRAVEL PATHS
In Telegraph of 23.8.14, the Ask A Builder column dealt with the following question from MW of Basingstoke …
“I want to install a gravel path around my house. Owing to the confines of the area, and the fact that it may be too expensive to pave, the gravel will be right up against the house. I’m making sure not to raise the level of the path above the damp-proof course (DPC), but how much lower should it be?”
Telegraph consultant Jeff Howell said:
“Ground levels adjacent to any building must finish at least 150mm (6in, or two brick courses) below the DPC. This is to prevent rain splashing off the ground and wetting the wall above DPC level, where it might track across and cause damp patches on the inside.
“Installing a gravel path or drive is not quite as simple as it might sound. If you just spread a load of gravel on to the ground, it might look pretty for a few months, but will soon sink into the earth, and become colonised with weeds.
“A properly constructed gravel drive or path is like an iceberg, in that 90 per cent of it is out of sight. You need to excavate and remove the topsoil, line the subsoil with a geotextile, then lay and compact hardcore. Follow this with a layer of compacted “hoggin” – compacted clay, gravel and sand. This is then sprayed with hot bitumen, and has a layer of pea shingle rolled into it. The final “wearing surface” of pea shingle is spread on top of this. So your finished gravel path is actually only two stones deep – one stuck into the bitumen, the other floating on top of it.
“Don’t forget that a gravel path also needs edge restraint – timber, brick or concrete kerbing, to stop the layers of stone and shingle escaping into the surrounding soil.
“I think you’ll find paving a lot easier and cheaper. You will still need to remove the topsoil, but you can then just line with a geotextile and bed the paving slabs on sharp sand.”
For more Jeff Howell, see http://www.askjeff.co.uk/

endsfornow

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