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DIY and home improvement

Last modified: Fri Aug 3 07:57:22 2007

This page contains some general tips on DIY, based on my own experiences. I expect to update this from time to time, as I get the opportunity. Have fun, and remember: don't force it, buy a bigger hammer!

Safety

• Be careful about getting up ladders with pointy objects in hand. It's unpleasant to fall off a ladder, but even more so to fall off a ladder onto a wallpaper scraper.
• Electric shocks hurt, and can be mostly prevented while doing electrical work simply by applying a neon test screwdriver to each terminal before touching it. This only adds a few seconds to the job, but reduces the risk of injury considerably, especially if you're up a ladder at the time.
• If a heavy electric drill falls out of a loft hatch, the bit will hit the ground hard enough to penetrate a floorboard. The image of my hammer drill stuck by a wood bit to the floor isn't one I shall forget in a hurry. Happily, no-one was walking underneath when it fell. Moral: don't put heavy or pointy objects on the floor near hatches or drops. Balancing tools on the rungs of ladders is a no-no as well.
• If you cut through a live cable with a pair of pliers, the fault current can generate enough heat to weld the jaws together. RCDs don't protect against this kind of foolishness, because the fault current is not to earth.
• If your house is more than about fifty years old, then any original paintwork that remains is likely to contain lead. Stripping this paint using a hot-air stripper or an electric sander could cause lead poisoning. Caustic paint strippers, although unpleasant in themselves, do not expose the user to this particular danger. But...
• It increases the effectiveness of caustic paint strippers if, as the old paintwork loosens, further liquid is forced into the bubbling mess using a stiff brush. However, there is a tendency for the bristles to spring back into shape and thereby spray droplets of caustic fluid into the air. This is therefore a job to do with the brush held at arm's length, because caustic paint stripper really, really hurts if it gets into the eyes.
• It is dangerous, and illegal, to fit a gas-burning appliance in a room that lacks permanent ventilation (unless the appliance has its own flue). Many people fit adjustable grilles over their air bricks to reduce drafts; the problem is that if the grille is closed the appliance may be starved of oxygen. This is a particular problem in modern, well-insulated houses, as they are designed to minimize extraneous airflows. A gas appliance that does not have an adequate oxygen supply will produce carbon monoxide in dangerous quantities. People often believe that the main risk with inadequate gas installation is that of fire or explosion; in fact carbon monoxide is a far more common cause of fatalities.
• Many gas cookers emit small amounts of carbon monoxide (CO) even with perfect ventilation. This is not dangerous, but is enough to give false alarms on some CO detectors.
• House-owners occasionally seal up unused chimneys to prevent rain entering them. Such chimneys are, of course, not an adequate source of ventilation. Check the airflow up a chimney before installing a fire under it.
• Unless you buy your house new, someone else will have lived in it before you. Not everyone is as careful and diligent in their DIY efforts as you are. Watch out in particular for:
  • ring mains that don't form a complete ring (the current carrying capacity is halved, but you can't detect a problem until the wiring overheats);
  • flat roofs that aren't sound enough to hold a person's weight;
  • blocked-up chimneys and ventilation points;
  • fuses of the wrong rating;
  • weakened or removed supporting walls;
  • weak staircases and associated fixtures;
  • inadequately fastened roof tiles (you'll know the first time there's a strong wind).

Painting and decorating

• It's fairly obvious that if a surface is smooth and well prepared it will look better when painted or papered than one that is lumpy and greasy. What isn't obvious, or at least wasn't obvious to me, is just how big the difference is. If you assume that you need to spend five times as long in preparation than in painting, you'll get better results than if you assume that the actual painting will be the long part of the job.
• Masking tape is widely used to protect areas adjacent to the area to be painted. If you take the masking tape off when the paint is too wet it will run, and make a mess. If you take it off when it is too dry, the edge of the new paint will come off with the tape. The window of opportunity between the `too wet' and `too dry' stages lasts about two minutes with modern, quick-dry paint. The more paint that ends up on the masking tape, the worse the problem is. If you use slower-drying paint, and don't assume that the masking tape can be freely painted, you can get good results so long as you pull the tape off at just the right time.
• If you stick masking tape onto a painted area, if you're really unlucky you can pull off the old paint as well as the new paint when you take it off. This problem is particular apparent if the area to be masked has not been painted properly. For example, you can apply gloss paint directly to wood in good condition, and it will look fine, but even masking tape will pull it away from the wood.
• Paintbrushes come in only two useful varieties: the shockingly expensive type that you cherish and pamper for many years, and the cheap nasty ones that you throw away after one job. Anything between these two extremes is not worth buying. Every time you clean a mid-priced paintbrush, the bristles get looser, and the next job is made harder. A really expensive brush can be cleaned over and over again and never lose a bristle.
• Cheap brushes shed most of the bristles they are likely to shed in the first few strokes. Make those strokes somewhere where you can't see them.
• Decorators' merchants and big DIY shops will make paint to an exact colour. You don't need to be buying a huge amount for this to be worthwhile. If you like a particular paint colour but it's only available in a `designer' range that costs the Earth, find it on the manufacturer's colour chart and get the colour made up from unbranded paint. It will cost about half as much, included the cost of mixing.
• Stripping wallpaper is one of the most unpleasant decorating jobs that you are likely to encounter. A steam stripper will make it a bit easier. A really heavy-duty stripper can be hired for about the same price as buying a cheap one.
• Plaster and filler all shrink as they dry. If you are filling cracks and holes in plaster prior to painting, don't worry too much about getting the surface perfect on the first attempt, as it will shrink anyway. Filling always needs at least two passes.
• It's easier to find all the defects in a plastered wall if it has a coat of fresh paint. If you plan to paint anyway, apply the first coat before repairing the plaster. But see below...
• Patching plaster and filler are usually white. With dark-coloured paint, if you paint before filling the defects in the surface, the white filler will be visible through the paint even after two further coats. The solution is to mix the powdered filler with paint, rather than water. Beware, however, the drying agents that are used in modern paints. A plaster that would normally set in thirty minutes with water may set in 10 minutes with paint.

Plumbing

• Even the tiniest speck of dirt is enough to prevent a soldered joint from taking hold. This sounds like plumbers' propaganda, but it's really true.
• If a solder joint doesn't take hold in a few seconds, it won't take hold in a few minutes either.
• Even the meagrest trickle of running water along the area to be soldered will prevent the joint taking.
• No heat-resistant cloth is effective enough to prevent you scorching the floor and walls if it takes you ten minutes to solder the joint.
• Soldered joints stay hot for a long time afterwards.
• Burned fingers stay burned for a long time afterwards.
• If a new joint feels damp when water is re-admitted to the system, if may just be condensation and not a leak. But don't push your luck.
• It's easier to move a radiator than to build furniture around it.
• For water plumbing, there are few good reasons to persist in the use of copper pipe and soldered joints. Plastic pipe and push-fit joints are trivial to assemble, at least as reliable, and can be dismantled if necessary.
• All pipework expands when it warms up. Plastic pipework expands rather more than copper, so needs a bit of extra space at the ends.
• Plastic pipework is unlikely to burst if the water in it freezes.

Electrical

• In an ideal world, the only places that connections are made in an electrical system are in the surface fittings (ceiling roses, switches, and power outlets). There should be no connections in inaccessible areas such as the space under floorboards. In practice, it is not always possible to achieve this, especially if you have to live in the house while doing the work. It is usually possible, however, with a bit of forward planning, to ensure that any under-floor junction boxes are in an accessible area (e.g., under a cupboard, not a washing machine).
• A mechanical cable stripper is really worth the money. Stripping cable with a knife or stripping hook is more hassle that you need. If a stripping hook slips while pulling through the cable, it can easily slice the entire length of your finger.
• Although the screw terminals on mains power outlets ought to be able to grip three wires in each terminal, it is often quicker to solder the wires before inserting them into the terminals, and then screw the terminal onto the soldered cable group.
• If you need to fit a large number of new flush-mounted outlets and switches, you can buy a special tool for cutting the rectangular holes (about £). This saves no end of time, a produces a near-perfect cutout. If you want to use the traditional method -- drilling many small holes to form a rectangular outline -- you can buy a template for a few pounds. This screws to the wall in the position of the required fitting, and guides the drilling to exactly the right shape and depth.
• You can also buy tools for cutting cable chases (the channels into which cables are recessed into walls). Prices start at a few pounds for a specially-shaped drill bit, and go up to hundreds of pounds for a proprietary chasing saw. A typical device has two circular saw blades mounted on the same axle and driven by a high-speed motor. Such a machine cuts a perfectly straight, uniform chase, with next to no effort. However, they are too expensive to buy for a job of smaller scale that rewiring an office block. You can hire one for about £30 for a weekend.
• Drilling templates and chases is incredibly messy. Even if you only work in one room, you will still find brick dust in all the other rooms in the house. This problem can be reduced by dampening the work area and/or holding up a vacuum cleaner hose to the area whilst drilling.
• A dual-gang 13-amp power outlet can be had for as little as 60p if you buy in bulk. Prices go up to as much as £10. What do you get for the extra £9.40? As well as looking nicer, the more expensive outlets are usually much easier to wire. Why? Because the terminals are arranged close together, rather being in places that lead to cheap construction. However, as all the different models conform to the same standards, you won't get a `better' or safer outlet for the extra money.
• A poor electrical contact can get very hot when a high current is flowing. In some circumstances it will get hot enough to melt the cable insulation, exposing the live conductors. A common cause of poor contacts in junction boxes and switch boxes is for the conductor to be trapped alongside the terminal screw rather than clamped down by the screw. Usually a really good tug on the cable will reveal any dodgy contacts of this sort.
• If you need to run a cable behind skirting board, you may be able to do this without removing the skirting by using a long drill bit to drill at a shallow angle behind the skirting and into the floor below. However, many walls have joists directly beneath them, so the drill may emerge into a joist rather than the floor cavity. The longer the drill bit you use, the shallower you can make the drill angle, and the less likely this is to happen.
• It should be obvious, but socket outlets designed for outdoor use are only properly waterproof if installed and used properly. In addition, there are different grades of weatherproofing for different applications. Most DIY shops sell socket outlets rated to IP54, which are intended to be safe for permanent outdoor installation, but not to be used when wet. These are intended to be used with ordinary 3-pin plugs, in dry conditions. Outlets rated IP66 are design to be usable when wet. An IP66 outlet will only give this level of protection when used with an IP66 plug -- an ordinary 3-pin plug should never be used in an outdoor socket when it is wet. You will only get full compliance with IP66 -- that is, safe wet-weather operation -- if you follow the installation instructions to the letter, which will generally mean gluing plastic caps over the fixing screw heads, among other things.

Joinery

• Whether you buy from a timber yard or a DIY outlet, long strips or battens of wood are prone to warping in storage. Check before purchase that the wood you are buying is straight. If possible, store it so that it isn't bending under its own weight.
• Kiln-dried timber contains about 10% moisture, compared with 15%-20% for air-dried timber. Air-dried timber will usually shrink when brought from the yard to a warm house; kiln-dried timber will usually expand a little. Kiln-dried timber usually requires less time to acclimatize, and is a bit easier to work, but is usually more expensive.
• By convention, timber dimensions are quoted as their unfinished sizes. If you buy, say, 3/4" by 3/4" battens planed smooth, they will actually be a bit smaller than this. 3/4" was the size before the wood was planed. Not all timer yards do this, but most do.
• Modern PVA wood glues will bond wood (if it is clean and evenly surfaced) more strongly than screws or nails. If you can ensure that a joint is held in place while the glue sets, then you don't need any other fastenings. However, PVA glue won't bond wood to plaster or mortar all that well, so you can't use it to put up shelves. Another problem is that the glue joint is so strong you can't dismantle it.
• You can get special-purpose drill bits that drill the pilot and shank holes for screws in one operation. That is, the drill bit has three separate bores: one for the pilot hole, one for the shank, and one for the countersink. This makes fixing screws very quick. However, you need exactly the right size for each screw. If you use a size 8 bit for a size 10 screw, the screw will go all the way in without biting into anything.
• You can make wood filler that matches the colour of the wood more-or-less exactly by collection the sawdust that comes off when you saw it and mixing it with PVA glue. The glue becomes transparent when it dries, leaving the colour of the wood.
• Electric jig-saws cut on the upstroke, not the downstroke like most hand-operated saws. This means that you should cut wood with the good side facing the bottom. [It's recently been pointed out to me that B & Q now sell jig-saw blades that cut on the downstroke, so this problem should be avoidable].
• I find it almost impossible to cut a perfectly straight line with an electric jig-saw. A circular saw is much better for this.
• Timber that is to form a load-bearing structure (deck, platform, treehouse) should almost never be fastened with nails. Although a large nail will stand a lot of force without breaking or bending, it can be pulled out of its hole too easily. Ideally, large structural timbers should be joined using bolts, perhaps combined with a metal joining plate. If bolts are impractical, the next best choice is usually coach screws. Coach screws are large screws with hexagonal heads, designed to be tightened with a spanner. Coach screws and bolts should always by used with washers under their heads. Otherwise the head will chew into the wood as the bolt is tightened.

Lofts and loft insulation

• There is no insulating material that is completely free of the propensity to irritate skin. Even hypo-allergenic materials like `Pink Panther' may cause irritation in some people. You still need a mask and gloves, at least, when handling this stuff. Some insulating material is supplied in a sort of plastic wrapper, which is designed to remain in place. This significantly cuts down the opportunity for skin contact with the fibres; but you will still have to cut it to length, so it's not a perfect solution.
• Loft insulation is, by its very nature, a poor conductor of heat. If you have electrical cables in your loft, and you surround them with insulation, this reduces their current carrying capacity by about 50%. This may not be a problem for lighting cables, but could be dangerous with, say, the power supply to an electric shower.
• If you insulate right up to the eaves of the roof, it will reduce airflow through the loft. You'll appreciate this reduction in draughtiness until your roof timers go rotten with damp. Then you won't.
• If you make a really good job of insulating your loft, it will get very, very cold in winter. There will be a much greater risk of burst pipework, as the risk of water freezing is increased. This means that you meant to be especially thorough in lagging pipes. The situation can be improved a bit by insulating the inside of the roof, as well as the floor. This means that any heat that does get into the loft is more likely to stay there, rather than warming up the sky. You need to be careful not to restrict ventilation around the wooden roof supports, or they will get damp from condensation.
• If your water supply is reliable, there is no functional need to have a cold water tank in the loft, or indeed elsewhere. Of course, if you experience frequent interruptions in water supply, or wild fluctuations in pressure, you may be better off with a tank. But in most circumstances you will do better to remove the tank altogether, and plumb all you cold water supplies to the main. In some areas this is illegal; water authorities favour the use of tanks because they even out fluctuations in demand (the biggest peaks in demand occur, I'm told, when people fill their kettles during the commercial breaks in television programmes). If you do remove the tank, you can re-route cold-water plumbing to avoid the loft. The advantages are considerable: better supply pressure, no further risk of pipework freezing in the winter, better cold-water quality (because it doesn't have to stand in a tank), reduced maintenance, and more space in the loft. Of course, even where tank-less operation is legal, water authorities take a dim view of the main supply becoming contaminated with, say, bathwater. This means that you will need to ensure that one-way valves are fitted wherever stales water could come into contact with fresh (shower heads, hosepipes, central heating feeders, etc.).
• It is relatively cheap, and not too difficult, to lay a proper floor in a loft. You can get `loft grade' chipboard flooring for a few pounds per square yard. If you are lucky, your joists will be of such a spacing that the flooring will fit without cutting. However, even if you have a solid floor, don't assume that you can necessarily use a loft as a `proper' room (for people and heavy furniture). The joists in a loft are often designed to support only the weight of the ceiling below, not a room above. To make habitable rooms in a loft may well require strengthening the timbers.
• Before deciding to lay a floor in the loft, check how any electrical wiring has been installed. If cables have been run along the top of the joists, then you'll have to re-route them before putting the floor down. This is a big job, and may only be worthwhile if you need to re-wire anyway.

Damp

• Although parts of a house can become damp rapidly as the result of a catastrophic leakage of water (a burst pipe, for example), even a small amount of water in the wrong place can cause dampness if it persists for years. For example, even a build-up of leaves can cause damp walls if it bridges a damp-proof membrane. If rain water does not drain away properly, but tends to accumulate against walls, this can cause problems too. Such problems can usually be fixed quite easily by scraping away fallen leaves and ensuring that gutters and drains are in good conditions. It is more troublesome when it isn't your gutter and drains that are the problem, but your neighbours'.
• Deposits of small crystalline material on the surface of plaster -- `efflorescence' -- is symptomatic of a potentially serious damp problem. This happens when water vapour pressure forces water out of the plaster into the air, where it evaporates and leaves soluble plaster compounds behind. Mildew, on the other hand, although unsightly, needs only small amounts of damp to take hold, and doesn't necessarily indicate a serious problem.
• Any part of a house that is below soil level is likely to be damp; there isn't a huge amount you can do about this. The trick is to ensure that the damp stays out of the bits of the house that people live in (if you live below ground, see below...) The damp-proof course installed in the brickwork of most houses is there for a reason: to prevent damp entering the parts of the house that are above ground. Anything that bridges the damp-proof course is likely to cause a problem eventually, even if it's just fallen leaves.
• You can get damp-resistant plasters and paints which may be useful if your damp problem is slight, but intractable. These don't fix the problem, but instead confine the damp to the brickwork. If the damp is pronounced, such a process may be counterproductive in the long term. Ideally, the water vapour should be free to evaporate into the air. Otherwise there is a risk of the brickwork becoming rotten and/or the plaster being forced off the brickwork altogether. If a room (e.g., a basement) is seriously, incurably damp, then it may be rendered usable by a process called `tanking'. This is effectively the construction of a new room inside the damp room. The new room is completely separated from the old one by a small air gap, and its walls are fastened periodically to the real walls by plastic (damp-proof) fixings. This is, alas, a specialist job, and I have never come across suppliers of tanking materials that are prepared to sell direct to the public. Consequently, it tends to be expensive.
• If your walls don't have a damp-proof course, or it has been bridged by new construction (e.g., stone cladding), you can simulate the damp-proof course by silicone injection into the brickwork. The equipment required to do this is expensive to buy, but relatively cheap to hire for a weekend.
• All forms of dampness are exacerbated by lack of air movement. Many people block up air bricks and ventilation holes because they think they create draughts; however, they are essential to allow evaporation (and to allow ventilation of gas-fired appliances).
• To me, damp plaster smells like cold baked potato. Whenever I smell baked potato in a house, I know that there's a potential damp problem. Or that somebody is baking a potato.

Flooring

• Floorboards usually creak because the nail-holes move relative to the nails when you step on them. The noise is made by the metal of the nail scraping on the wood. This is a bigger problem with older floors because the wood will have shrunk since the nails were hammered in. With an electric screwdriver and a pilot drill you can screw down all the floorboards in a good-sized room in an hour or two. Then they won't creak at all. This treatment is probably not appropriate if you want a wooden floor to remain visible, as a floor full of screw-heads is rather ugly,
• Any floor varnish strong enough to stand the wear it will encounter in a busy house is likely to be extremely noxious. If you can apply the varnish without having all the doors and windows open, it probably won't last all that long.
• Contrary to common belief, my experience is that you can fit laminated wood floors in a bathroom and get long service from them. However, you can't expect the factory-applied varnish to offer suitable water protection: you'll need to apply a few coats of specialist heavy-duty floor varnish. Otherwise the humidity will warp the wood.
• Surprisingly, in some houses the walls are built on top of the floorboards. This is mostly likely to be the case for non-load-bearing walls. If you think you can lift a floorboard without cutting it, by pulling it up from the end, you may be out of luck: you'll be trying to lift the house.
• If you try to lay perfectly square tiles on a floor that is slightly curved, even if it's perfectly smooth, the edges of the tiles won't meet in all the places they should. This is less of a problem with ceramic tiles, because the small discrepancies can be taken up by filling the gaps with grout. It is very apparent with vinyl or carpet tiles, because they are designed to butt together in perfectly straight lines. If your floor is, for example, inch higher in the middle of the roof than at the edges, this will be enough to stop the tiles fitting properly. The problem is easily fixed by cutting occasional tiles to the proper shape -- you will usually only need to trim a few millimetres off -- but you'll get poor results if you expect tiles to fit perfectly without trimming. It is easy to find whether you have this problem by laying a rectangular patch of few dozen tiles without glue, and seeing whether they butt together properly.
• Chipboard and plywood of the appropriate grade make a good alternative to traditional floorboards, and can be laid quickly in large sheets. Moreover, when properly installed the sheet wood will form a rigid structure with the joists, and distribute load across multiple parallel joists -- something that is impossible with floorboards. However, suitable wood is usually 3/4" (19mm) thick -- anything thinner will not be strong enough to stand ordinary floor loads -- and therefore expensive and heavy.

Tools

• It really is true what they say: any job is much easier with the proper tools. I've lost count of the number of hours I've wasted over the years trying to put in screws with a screwdriver of the wrong size, or tighten up bolts with pliers rather than a spanner.
• The difference between `professional quality' and `DIY' tools is not that the professional tools are bigger, more powerful, or more feature-laden. In fact, very often the opposite is the case. The extra money you pay for `professional' tools is reflected in two things: the build quality, and the availability of spares. Expensive tools are those that are designed to be used all day, every day. For occasional use, you might not need to spend so much money. It's as true with tools as it is everywhere else that you get what you pay for; but in some cases what you get for a little money is sufficient.
• I have not yet come across any battery-powered tool, however expensive, that is as powerful or effective as its cheaper, mains-powered counterpart. Of course, battery-powered tools are more convenient.
• There are all sorts of odd tools available for specialist jobs, and they aren't always that expensive. If you come across a really awkward job, and feel deep down that there ought to be a special tool for it, there probably is. For example, you probably won't find the tool for making rectangular cut-outs for electrical outlets in a DIY shop, but such a thing is available from specialist tool suppliers. It's worth browsing through a tool supplier's catalogue if you're stuck for a way to do a difficult job.

Weatherproofing

• Rain is incredibly intrusive. It can get through the smallest cracks in woodwork or roofing material. The worst culprits are usually felted flat roofs, and it's worth trying to avoid building a flat roof at all if you can. You can get repair sealants for felted roofs, but even the best quality roofing felt rarely lasts more than about 15 years, after which it will have to be pulled up and replaced.
• If water is dripping into your house, don't expect the hole to be directly above where the drip appears.
• The lifespan of an untreated wood structure that is directly exposed to direct sunlight and rain might be as short as a year in the UK (probably less in countries which experience harsher conditions). Exterior-grade factory-treated timber will last a bit longer -- a few years. In direct contact with soil, such timber will probably rot all the way through in in two to five years. In short, you should apply at least two coats of good quality wood preserver to any exterior wood. Everyone knows that untreated, or lightly treated, softwood will degenerate when used outdoors, but it's surprising how alarmingly quickly this can happen.
• Sawn timber joists and beams absorb water preferentially through their ends -- this is where the wood fibres are cross-cut. Ideally long timbers intended for exterior use should be stood on their ends in a bath of wood preserver until the fluid has risen up the fibres by capilliary action (usually a couple of hours). This is crucial for timbers that will be in, or on, the ground.
• Although not very sightly, corrugated plastic sheeting is easy to work, light, and 100% waterproof if installed properly. You should use rubber washers are the screws used to fix it, otherwise water will ooze through the gap between the screw and the plastic.

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