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Replacing First floor joists

Postby bouncy35 » Sun Feb 03, 2008 6:05 pm

Hi - I have just moved into a new house which has had its loft converted to two bedrooms.

I noticed that the floor in one of the bedrooms flexed and was not level and also that the ceiling in the rooms beneath were cracked and shedding artex. So after some investigation I found that this one room had not had the correct size joists added when the loft space was converted and hence over the years the 3x2 ceiling joists had flexed and were getting worse.

So I have replaced them with 7x3 (i need the 3 due to the span and the restriction that I cannot raise the floor level when I put the boards back down) and they are good and solid now.

My questions are:

1. Do I need to insulate the void between the joists (i.e. between floor and ceiling) and if so what is the best, easiest, most cost effective and least irritating material? Also what thickness of material? Do I need to leave a ventilation gap and ifo so on which side - above or below the insultation?

2. What are the requirements for floor boards. I think I will use chipboard but what thickness (joists are at 400mm centres) and what size boards are best - bear in mind I have to get them upstairs.

3. I have some cables that will need to be run perpendicular to the joists under the chipboard. Is it OK to notch the joists to run the cables? Should I put metal protectors over the cables once they are run? (I saw something in screwfix for this?)


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