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An electrician meditating, Ohm...

I've just published a book on DIY. It's blank and comes with a free pen.

Hi This happens time after time, intermitant faults are allways the worse. Trouble is, it makes you feel such a fool. Lets hope it keeps on working OK.

Hi All Am hoping to install a roof drain in a newly covered felt flat roof. this is due to an area that ponds. I would like to use a normal rubber outlet cut through the deck and seal with cold applied sealer such as liquid rubber. Anyone done anything similar? Which product, method etc.? Thanks in advance

There used to be a real problem with putting Thermostatic Radiators Valves (TRV’s) on the return. As the TRV just opening or closing the dynamics of the flow would cause the valve to snap shut and then open repeatedly, this sounded like a machine gun. Most TRV’s are now bi-directional (as yours is) that is they can be fitted on the flow or the return. In your case pipe the radiator as is and put the TRV on the side with the best air flow.

just to add to diy guy's comments... a few drops of washing up liquid in the mix works as a poor man's plasticiser. mortar should never be stronger than the substrate you are working with... in other words when movement occurs due to changes in temperature or moisture the mortar should give a bit instead of cracking the brick, tile, etc., or simply becoming detached. 4:1 represents a strong mortar for best brick, again depending what sand is used (using a softer or finer sand tends to produce a stronger mortar but a more pleasing pointing). softer or weaker substrate would need a weaker ratio down to 7:1 for some jobs. it is still important that ordinary portland cement is fairly fresh and in good condition for best results... it is doubly important that mortar is allowed to "cure" rather than just dry out. consider bricks are very absorbant - like sponges - it is not surprising that in the old days brick piles were continuously soaked with a hose prior to being laid during dry spells to prevent this problem. i suspect this is the basis, or the majority of eddief's problem with his weak bonding mortar.

if your roof is felted under the tiles the polyeurethane foam or whatever they spray on cannot hope to bond the tiles together unless they cut or tear away the felt first... this could then be a good way of stabilising a failing roof - as far as the bits between the rafters is concerned! any leaks above the timbers is unlikely to be sealed leaving the timber open to attack by nasties. a few soffit vents are unlikely to help. i think this process is best suited to insulating steel based industrial type roofs and kept away from timber and tiles (probably how they have remained in business 40 years). it might be ok making a good roof stay good for longer but i think it should be kept away from a failing roof. a dislodged tile or one holed by frost is unlikely to cause a troublesome leak if the underfelt is ok - so it probably isn't that good. some roofs weren't felted at all when new. quite alarming to be able to bird-watch through the gaps but watertight except in driving rain, and snow was a bit of a problem. our tiles were laid on bundles of reeds which would have lasted more than the 130 odd years if jerry hadn't chucked a few bombs at our street... if good secondhand tiles are available to match your own you have an extra option available to you - having the roof stripped, refelted and relaid, which can be a big saving over the cost of a re-roof. it could be as little as half the cost. get together with a neighbour so the scaffold doesn't have to be moved far and the cost continues to fall, especially if you choose a roofer with his own scaffolding. i suggest you take a flask of coffe up into your roof space and examine the underside of your roof to see what you can learn; as well as deciding for or against timber treatment against worm and measuring for additional loft insulation. could be you might be eligible for some grants... some research about the reputation of local roofers would be in order... try finding out which one has the contract to maintain the local public buildings or ask your local builders merchant to suggest a couple...