Replacement trusses for loft conversion

[FingersAndThumbs]

I'm blessed with a 70s bungalow with a low pitched roof. Around 20m x 8m.

 

I'd like to create an upside down house, leaving the current layout pretty much as is and create a large open plan space upstairs.

The idea is to replace the roof trusses with 45 degree attic trusses or equivalent ridge beam and SIPS panel roof.

 

If the foundations can take it, what are the gotchas over adding a roof to a new build? One issue I thought may be upsetting the current ceilings, but Moduloft seem to be able able to keep these intact.

 

Thoughts greatly appreciated!
 

[Big Jimbo]

IMO the biggest problem will be planning.

[joe90]

Yes, first hurdle will be planning.

[FingersAndThumbs]

Cheers @Big Jimbo and @joe90, but if we assume planning is in the bag....

 

We're not overly near other houses and the only bungalow in the vicinity.

[Big Jimbo]

8 meters even at 45 degree pitch won't give you a huge room. In my opinion you would be better off considering adding perhaps a half storey in timber and then a pitch at a shallower degree. This would give you the footprint that you have downstairs, with eaves at perhaps 1.2 plus metres. Much more usable space.

[Mr Punter]

You may as well incorporate dormers.  You will need a scaffold temporary roof.  The trusses will be big and heavy.

[Temp]

2 hours ago, FingersAndThumbs said:

One issue I thought may be upsetting the current ceilings, but Moduloft seem to be able able to keep these intact.

 

The best way to preserve existing ceilings is to avoid putting any new load on the existing ceiling joists. Arrange for the bottom of new floor joists (or bottom of attic trusses) to be about 1" above the top of the plasterboard. Avoid bolting or nailing new joists to the side of existing ceiling joists except at the ends where the existing joist is supported by a wall. That way when you load them up and they bend they do not transfer any load to the existing ceiling. This should really help avoid cracks in ceiling plaster.

 

 

Edited September 26, 2020 by Temp

[joe90]

I just watched the moduloft video and it looks very comprehensive, but what cost?

[Big Jimbo]

1 minute ago, joe90 said:

I just watched the moduloft video and it looks very comprehensive, but what cost?

Very expensive from what i have heard.

[joe90]

6 minutes ago, Big Jimbo said:

Very expensive from what i have heard.

It certainly looked it, but some would pay it for a quick job I guess?

[Big Jimbo]

1 minute ago, joe90 said:

It certainly looked it, but some would pay it for a quick job I guess?

I have heard that the price would make your eyes water. It is basically, a finished product craned onto the top of the existing, so would defo save a load of time.

[FingersAndThumbs]

The price quoted was £140k + VAT, so not cheap but could have been scarier. That was for four bedrooms with dormers plus bathroom, rather than one big open space. Four weeks to install.

 

Rather than going down this route, I was hoping that I could get something watertight and then I could take over from there.
 

[FingersAndThumbs]

1 hour ago, Big Jimbo said:

8 meters even at 45 degree pitch won't give you a huge room. In my opinion you would be better off considering adding perhaps a half storey in timber and then a pitch at a shallower degree. This would give you the footprint that you have downstairs, with eaves at perhaps 1.2 plus metres. Much more usable space.

 

Good point. Just thinking about bang for the buck. Would this increase cost significantly, do you think?

[FingersAndThumbs]

 

1 hour ago, Temp said:

 

The best way to preserve existing ceilings is to avoid putting any new load on the existing ceiling joists. Arrange for the bottom of new floor joists (or bottom of attic trusses) to be about 1" above the top of the plasterboard. Avoid bolting or nailing new joists to the side of existing ceiling joists except at the ends where the existing joist is supported by a wall. That way when you load them up and they bend they do not transfer any load to the existing ceiling. This should really help avoid cracks in ceiling plaster.

 

 

 

Brilliant, thanks. Makes sense. I was wondering about electrics too. I guess that if the new joists are above the current joists then the wiring could sit in that cavity?

[Big Jimbo]

7 minutes ago, FingersAndThumbs said:

 

Good point. Just thinking about bang for the buck. Would this increase cost significantly, do you think?

At 45 degree pitch, with much larger floor joists than your existing ceiling joists i would guess at an inside apex point of 7.5 mt. So say dwarf walls either side of 1.2 mt,  might end up with a room 4.5mt wide but with sloping ceilings either side. I expect that the actual 6ft tall person would have about 3.5mt x 20mt, if gable ends to walk around. Less the space for the stairs. Fitting kitchen units, fridge freezer etc, will be a pain with sloping ceilings. I find sloping ceilings quite oppressive. The result i feel would be a dissproportunate long thin room. And i would want a toilet up there. I don't want to have to go downstairs for a wee. My option would cost you more, but the extra square footage would prop pay for the extra cost in value.

[FingersAndThumbs]

13 hours ago, Big Jimbo said:

At 45 degree pitch, with much larger floor joists than your existing ceiling joists i would guess at an inside apex point of 7.5 mt. So say dwarf walls either side of 1.2 mt,  might end up with a room 4.5mt wide but with sloping ceilings either side. I expect that the actual 6ft tall person would have about 3.5mt x 20mt, if gable ends to walk around. Less the space for the stairs. Fitting kitchen units, fridge freezer etc, will be a pain with sloping ceilings. I find sloping ceilings quite oppressive. The result i feel would be a dissproportunate long thin room. And i would want a toilet up there. I don't want to have to go downstairs for a wee. My option would cost you more, but the extra square footage would prop pay for the extra cost in value.

 

Thanks @Big Jimbo.

 

Wife has already mandated a toilet upstairs!

 

Hear what you're saying. By building up the walls I'd get double the floorspace for most likely a good bit less than double the build cost.

What happens to the outside walls on the upper floor? Single brick skin?

[Big Jimbo]

1 hour ago, FingersAndThumbs said:

 

Thanks @Big Jimbo.

 

Wife has already mandated a toilet upstairs!

 

Hear what you're saying. By building up the walls I'd get double the floorspace for most likely a good bit less than double the build cost.

What happens to the outside walls on the upper floor? Single brick skin?

How about cladding them. Timber, or cement board.

[FingersAndThumbs]

21 hours ago, Big Jimbo said:

How about cladding them. Timber, or cement board.

I was thinking of cladding, but over the brickwork. Just cladding over the wooden frame gives me the wobbles. Guessing unfounded.

[joe90]

5 minutes ago, FingersAndThumbs said:

I was thinking of cladding, but over the brickwork. Just cladding over the wooden frame gives me the wobbles. Guessing unfounded.

Oh yes, there are very many timber framed houses, some hundreds of years old!!! Just needs designing properly.

[john0wingnut]

Interesting thread.

 

Im in a similar position with my bungalow and am looking at adding another storey on top under the new PD planning rules.

 

From what I’ve been advised is that so long as it’s the size of the ground floor, on the existing structure and the new ridge is not higher than 17m (that might not be quite correct) it can now be done under PD.

 

I am also in a similar position with wanting to preserve current ceilings and as mentioned above, proposal is to have new joists put in several inches above current ones to allow for the pipe and wire runs currently in situ.

I will be looking at timber frame, with cladding, and had a similar idea of getting a water tight structure on, then finishing it off myself at my pace internally.

 

I was also advised re the scaffold roof being required whilst the current roof is removed and new walls and roof added.