Replacing floor joists


Postby TJ » Fri Apr 13, 2007 2:53 pm

I have to replace some of my floor joists which have rotted. Our house is very small, only 12 feet wide with one sleeper wall between the out side walls on either side. Due to the size of the rooms there is no way of installing a full joist without cutting it. Am I right in thinking that I can join two pieces together on the sleeper wall with timber connectors and if so how should I best do this. To my way of thinking I could either over cut the pieces and rest the offset piece in a joist hanger or alternatively cut the joist to exact size and then cut in half and sandwich the two pieces between two shorter lengths of timber on the sleeper wall. Any advice would be very welcome.
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Postby thedoctor » Fri Apr 13, 2007 4:45 pm

The joists are usually cut to overlap each other by 1m and sit on the wallslightly offset to allow the overhang to go past. The joist are then bolted to each other to stop seperation. If its necessary to have both joists on the same plane, then they are laid as above but a new section is then planted onto the side of the joist that is offset. If they are only rotten at the ends, see our repairing structural timber project where you can see how to repaitr them easily without replacing them.
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Postby TJ » Fri Apr 13, 2007 5:45 pm

Thanks for the advice doctor. The joists are decayed for most of their length probably as a result of the airbricks being blocked over the years. We've only had the property for 12 months and it was used as a holiday cottage for many years. So far I have found 3 joists which need replacing but I think there are likely to be more. We can't vacate the property so we'll have to go from room to room until we've finished. A summer job I think! Any suggestions about bolt sizes and numbers?
TJ
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Postby T E Partington » Tue Apr 17, 2007 12:08 pm

the reason for the rot is that the house has no damp course and the timbers sit directly on the brick, when replacing it is better if you can remove some of the brickwork above the joist at one end and you may find the recess at the other end is deeper than required, you can push a timber into the recess drop it in where you have removed a few bricks and install a comlpete joist, dont forget to sit it on slate or damp proof membrane (not polythyne) because your new timber will rot much faster than your old good quality ones, try to keep the floorboards from touching the brickwork too, hope this helps, Tim.
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Postby thedoctor » Sun Apr 29, 2007 7:36 am

Take a look at the project in the DIY projects section called repairing structural timber. The company in there, Property Repair Systems, will give you free, no obligation advice on the phone. Their number is well publicised on their site.
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