Alan

A I am fairly certain that if, as you say, the chimney is slightly lower than the apex of the roof then this is your problem. If a chimney flue pipe is positioned up to maximum of 600mm away from the ridge, then the height of the chimney stack must be 600mm above the ridge. If the chimney flue pipe is 600mm or further away from the ridge, then the chimney stack must be a minimum height of one metre above the highest point of contact with the roof. A chimney that does not extend above the ridge may well cause problems with downdraughts. It is recommended that all chimneys, regardless of positions on the roof, should extend above the ridge height.

Q I own a 1930s house with wooden floors on the ground floor. It has recently come to light that my sitting room floorboards and joists suffer from wet rot. The floor started to collapse in several corners of the room; on taking up these parts of the floor (which were completely rotten) the underside of the rest of the floorboards and joists appeared wet. The underside of the floor has dried out well since the rotten floorboards were removed several months ago . . . I think the wetness may have been due to a combination of poor underfloor ventilation and a solid maple floor (with plastic underlay! ) covering the floorboards. My question is; what remedial work should I now undertake? Would it be best to replace the entire wooden floor with a solid concrete floor (area is approximately 15 sq m)? Would this be extremely expensive given that there is a two-foot underfloor space to be filled, or are there any other pitfalls with this approach? If I were to install a new wooden floor I would be concerned that rising damp in the external walls or underfloor supporting walls would lead to further rot, or should a builder be able to take steps to prevent this? Would a suspended concrete floor be an option?

Colm McDonald

A One problem, so many ways to rectify! Most people would say to put in a new concrete floor. However, one drawback is that the concrete is poured on top of floor insulation which in turn sits on a 1200-gauge polythene damp-proof membrane. If you were to go by the rules regarding concrete floors, this damp-proof membrane is supposed to lap under the damp-proof course of the rising walls. This is not possible in your situation as the walls are already built. You say there is rising damp in the walls; this is your second problem. You need to cure this before doing any other work or you will have more problems in time. If you want to put in a suspended timber floor I suppose technically this would be the correct way to go. However, you still need to put some form of damp-proof course in the walls, whether by drilling holes and injecting the walls with damp-proofing liquid or by installing a damp-proof course by cutting out sections of wall and bedding in the DPC at the appropriate level and then bricking up the openings you have made. The type of external walls in your house will determine the next step. If you have brick walls you can cement in joist hangers at the correct level and then fit your floor joists into these. If not, you can fix a timber trimmer to the wall, then fix your joist hangers onto these. I would suggest using treated timbers throughout the floor. Don't forget to make sure there is plenty of underfloor ventilation to prevent rot. You also need to consider insulating the floor.

This can be done by attaching 1200-gauge plastic to the sides of the joists using 2" x 1" timbers. The plastic will hold the insulation in place.

There are many ways of undertaking this job. You really need to get a competent builder in to assess the situation and provide a quote.

Q I fitted a garden gate but the gate post has come loose. I tried tightening the screws but this doesn't work. Any ideas? Michael Lyons Use of incorrect-sized fixings and poor quality tools will result in this happening. Your best bet is to fix the posts to the wall with compression anchors. These are a hammer-in fixing, very easy to use.

A First measure the thickness of the timber post. As a minimum you need to double this measurement to give you the length of the anchors needed. A safe bet would be to use 150mm fixings. Drill a hole using an 8mm bit of sufficient length, then just hammer in the fixing. Be careful to hit it straight.

WRITE TO US If you have a building/renovation-related query you'd like Steve to help you with, email doorstepdoctor@tribune. ie

Steve Guerin is managing director of www. tradesmenireland. com, the website that will help you find a tradesman, site for sale, property to rent or buy and all the plant and machinery you need to complete your house build or renovation