New joists for loft rooms

[wwwebber]

Hi, the joists in my two loft rooms are only 3x2 and I'd like to make them into proper fully usable rooms (1820's property). So, one of the first jobs would be to install new 7x2 joists alongside the old ones. However, I cant afford to lose any height in the loft rooms but have plenty to play with in the rooms below so I plan to remove the old first floor ceilings and install the new joists from underneath and thus negate the need to remove the existing flooring above. Most of the ceilings need re-boarding and plastering anyway.

A couple of questions :-

• Any issues with this approach ?
• Can I use the existing wall plate ? assuming there is one of course !

Thank you.

 

[John D v2.0]

Sounds like a messy job but I guess you know.
My concern is if you reuse the wall plate it will be too high. You'd have to lower it by 4 inches to rest the new joists on it.

 

[wwwebber]

Sounds like a messy job but I guess you know.
My concern is if you reuse the wall plate it will be too high. You'd have to lower it by 4 inches to rest the new joists on it.

ok, I thought instead of the new joists being proud of the wall plate then it would overhang instead ? - is this wrong ?

 

[wwwebber]

Just thought - the property was built circa 1820 so will more than likely not have a wall plate on which to use joist hangers ?

 

[John D v2.0]

ok, I thought instead of the new joists being proud of the wall plate then it would overhang instead ? - is this wrong ?

If it's a normal wall plate The old joists will be proud by 3 inches, the new ones by 7 inches

Just thought - the property was built circa 1820 so will more than likely not have a wall plate on which to use joist hangers ?

Not sure if you can use hangers on a wall plate without strapping it down. You could maybe notch it and hang, but you'd need someone who knows what they're talking about and ideally on site! I don't.

 

[freddiemercurystwin]

Assuming the hangers could actually be fitted correctly how will you get the joists in when normally they would be lowered down into the hangers? Sounds bonkers.

 

[bobsuerita]

you need an engineer dont go bodging it
you will regret it and cost more in the long run

 

[Doggit]

The existing joists may well have sunk slightly in the middle, so you wouldn't be able to get the new joists set in properly, therefore best you go for broke webber, and lift the floor remove the 3x2s, and then install the new ones. The ceiling joists may be sitting on a wall plate, and you'll use joist hangers folded over the wall plate to get the height correct, and then set the first noggins by the wall plate to provide rigidity. Or you could notch the joist ends so they sit on the wall plate as well as the joist hangers. Oh, and you're going to have to take down the dwarf walls as well I'm afraid.

But because of it's age, you may not have a wall plate for the joists, so you really need to take up up the floorboards at the edge, and then get back to us. There is another way that you can do, but that would involve a bit more work, so we'll leave that till later.