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Wrong size roof joist installed by builder

I have an extension being built at the back of the house which is 6mx8m. Now the plans state a joist size of 47x195 C16 yet the builder has used 50x175 C16. So I am worried now whether the inspector will allow this as the plans state otherwise. The builder has now completed the whole roof ready for inspection, is this likely to be a problem? The distance between two supporting wall is 3.78m.

Edit:The extension is rear single story and will never be approved for another story as it is a rear extension. So the weight on the joist is just that of the roof above it which can never pose much a problem to the supporting limit of the joist. I think the bigger joist requirement is due to the span between the two supporting walls. Anyhow the inspector is coming tomorrow and we will see how it goes. One thing though if the inspector said ok can he then object later on?

2 Answers from MyBuilder Extension Builders

Best Answer

Hi, this all depends on if you have had structural calculations done? If so then yes, it will be necessary ( for your piece of mind if nothing else) to make sure this joist correlates with the plans. If building control pick up on it when signing the job off it will cause you a world of problems, if its easy to fix this now then my advice is do it.. It may save you and your builder time and money in the long run. Hope that helps.


Answered 15th Sep 2015

When you say "the plans", do you mean the approved building control submissions? If yes, then I think Building Control may well require the minimum approved dimensions to be installed. Or, they may accept it if the new work is in some way upgraded to achieve the same as it would have if the correct size timbers had been used.

Best thing, invite them around to comment.

Thanks, Jason.


Answered 15th Sep 2015

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