Flooring out my garage loft - advice needed
Discussion
Recently moved into a new house with a large detached garage (20ft x 30ft). The guy selling the house was a joiner and with the assistance of a local builder did the garage himself.
He told me that it had been designed/built to be ready to have an upstairs added a later date but he'd never had the time to finish it...
Now before I get up there and start laying boards (and end up bringing down the roof) I was wondering if anyone can advise whether this sounds true.
The cross beams are 7" high by 2" wide and spaced at 24" intervals. Does this sound adequate for a loadbearing floor over a 20ft span? The A frames are of the type with the vertical struts and plenty of head room so that isn't an issue and there are velux windows and electrics up there already.
I'm sure it would be fine if it was just for storage, but I would like to get a staircase in there and turn it into a games room.
If I'm going to need to add addtional metal I-beams then so be it, but don't want to if I don't have to!
On a different note, would planning permission theoretically be required to do this (in Scotland)? The garage was fully permitted when it was planned but was eventually build outwith the building warrant as the term had expired. A Letter of Comfort was issued by the local authority before I bought it so although this has all been closed out, I don't want to cause problems for myself. I don't know if the original permission/warrent had a floor shown on it. I presume if I go the route of new planning permision, I will need structural calculations etc...
Any advice would be appreciated!
Cheers
Matt
He told me that it had been designed/built to be ready to have an upstairs added a later date but he'd never had the time to finish it...
Now before I get up there and start laying boards (and end up bringing down the roof) I was wondering if anyone can advise whether this sounds true.
The cross beams are 7" high by 2" wide and spaced at 24" intervals. Does this sound adequate for a loadbearing floor over a 20ft span? The A frames are of the type with the vertical struts and plenty of head room so that isn't an issue and there are velux windows and electrics up there already.
I'm sure it would be fine if it was just for storage, but I would like to get a staircase in there and turn it into a games room.
If I'm going to need to add addtional metal I-beams then so be it, but don't want to if I don't have to!
On a different note, would planning permission theoretically be required to do this (in Scotland)? The garage was fully permitted when it was planned but was eventually build outwith the building warrant as the term had expired. A Letter of Comfort was issued by the local authority before I bought it so although this has all been closed out, I don't want to cause problems for myself. I don't know if the original permission/warrent had a floor shown on it. I presume if I go the route of new planning permision, I will need structural calculations etc...
Any advice would be appreciated!
Cheers
Matt
& if you are wanting to do it properly you will need to protect the room upstairs by 1/2 hour fire resistance.
This can be achieved by plasterboard & skim finish to the under side of the joists.
Google joist span tables to find out the size you really need in there!
If you are stuck and in the Lanarkshire area I know a fantastic ex Building Control officer who could help you out! :-)
This can be achieved by plasterboard & skim finish to the under side of the joists.
Google joist span tables to find out the size you really need in there!
If you are stuck and in the Lanarkshire area I know a fantastic ex Building Control officer who could help you out! :-)
Busamav said:
So they are trusses .
Is the cross bracing at an angle .........or is there just one vertical member in the eaves each side .
If neither of the above , then 7x 2 floor joists on their own at that span are woefully inadequate for a domestic floor loading
A-frames not the right terminology? Think I just have the one vertical member each side of the truss... see pic below in ase I'm confuisng things... Is the cross bracing at an angle .........or is there just one vertical member in the eaves each side .
If neither of the above , then 7x 2 floor joists on their own at that span are woefully inadequate for a domestic floor loading
I guess that means this is woefully inadequate then?
Another to add to the list of lies I was told then. Sounds like a professional conversion is required then. Boo.offshorematt2 said:
I guess that means this is woefully inadequate then? Another to add to the list of lies I was told then. Sounds like a professional conversion is required then. Boo.
On the contrary judging by the pic I'd say like it looks ripe for conversion. Another to add to the list of lies I was told then. Sounds like a professional conversion is required then. Boo.They are attic trusses which are perfect for this kind of conversion.
Also the use of 7" x 2" joists suggests that they are not just there to support the ceiling.
herbialfa said:
& if you are wanting to do it properly you will need to protect the room upstairs by 1/2 hour fire resistance.
This can be achieved by plasterboard & skim finish to the under side of the joists.
Google joist span tables to find out the size you really need in there!
If you are stuck and in the Lanarkshire area I know a fantastic ex Building Control officer who could help you out! :-)
Yeah, I was intending to plaster the roof in the garage at some point anyway.This can be achieved by plasterboard & skim finish to the under side of the joists.
Google joist span tables to find out the size you really need in there!
If you are stuck and in the Lanarkshire area I know a fantastic ex Building Control officer who could help you out! :-)
Just had a play with some online calculators. Bearing in mind that I'm guessing at a lot of the inputs, it seems the maximum span is only around 8ft?? If I assume 2x8 rafters instead of 2x8 floor joists (no 2x7 in the lists), I can increase this to just 16ft. I assume these tables have a whole ream on contingency built in? In my industry there is 100% safety factors on everything - I hope it's the same here!!
Maybe I need to give up on this idea until I can get some professionals in to do the conversion. Am I right in thinking additional metal I-beams would be a solution, or would I need to build supporting pillars?
B17NNS said:
offshorematt2 said:
I guess that means this is woefully inadequate then? Another to add to the list of lies I was told then. Sounds like a professional conversion is required then. Boo.
On the contrary judging by the pic I'd say like it looks ripe for conversion. Another to add to the list of lies I was told then. Sounds like a professional conversion is required then. Boo.They are attic trusses which are perfect for this kind of conversion.
Also the use of 7" x 2" joists suggests that they are not just there to support the ceiling.
I suspect they have been designed for conversion as the seller said.
If it were me , I would be cracking on as they are .
Edited by Busamav on Sunday 6th December 16:54
Busamav said:
B17NNS said:
offshorematt2 said:
I guess that means this is woefully inadequate then? Another to add to the list of lies I was told then. Sounds like a professional conversion is required then. Boo.
On the contrary judging by the pic I'd say like it looks ripe for conversion. Another to add to the list of lies I was told then. Sounds like a professional conversion is required then. Boo.They are attic trusses which are perfect for this kind of conversion.
Also the use of 7" x 2" joists suggests that they are not just there to support the ceiling.
I suspect they have been designed for conversion as the seller said.
If it were me , I would be cracking on as they are .
Edited by Busamav on Sunday 6th December 16:54
Excuse my ignorance, but what in the picture has changed your mind? Initially, the span for the beam size sounded too great, but I guess the truss design makes it more acceptable? It's been a lot of years since I studied structural engineering, and I don't think I understood much more than the basics even then
Is the span between the uprights the bit I should be looking at?Re the comments about adding 9x2's, if it comes to that, these would be significently cheaper than metal I'm sure and puts me back in the realms of DIY. Don't fancy lifting rows of slates though...
I didnt change my mind , I just wasn't 100% sure what you were describing
I was hoping they were Attic trusses but A frames can mean all sorts .
Attic trusses are the way forward , I cringe when I see developers put ordinary trusses in to a build.
I have seen 8 + metre attic trusses with only a 200 bottom chord .
If you intend to proceed without a building warrant , for your benefit ensure you put the correct insulation and ventilation in .
Please remember , it really doesnt cost much more to do the job 100% correect.
As for the garage ceiling , insulate that well and put at least 2 layers of 12mm plasterboard as a ceiling .
If you need more detail just fire away .
ps looking quickly at the span charts , 9x2 at 400 ctrs doesnt even make 5m , but you dont need additional support with attic trusses .
Why not contact the truss supplier and ask them for confirmation just to sleep well .
I was hoping they were Attic trusses but A frames can mean all sorts .
Attic trusses are the way forward , I cringe when I see developers put ordinary trusses in to a build.
I have seen 8 + metre attic trusses with only a 200 bottom chord .
If you intend to proceed without a building warrant , for your benefit ensure you put the correct insulation and ventilation in .
Please remember , it really doesnt cost much more to do the job 100% correect.
As for the garage ceiling , insulate that well and put at least 2 layers of 12mm plasterboard as a ceiling .
If you need more detail just fire away .
ps looking quickly at the span charts , 9x2 at 400 ctrs doesnt even make 5m , but you dont need additional support with attic trusses .
Why not contact the truss supplier and ask them for confirmation just to sleep well .
Edited by Busamav on Sunday 6th December 18:22
What are you planning for the floor material? 2ft is a lot for floorboards etc. to span. I'd attach 2x2" to each side at the top of the 7x2" to form a T-beam which will stiffen up the span, reduce the floorboard span and help with continuity across the splice plates. Drill a series of 1"dia holes in the centre(or 1/2" above the centre) of the 7x2"s for the electrical installation wires. Don't bother flooring on the outside of the hangers.
Thanks for all the advice. Just to put minds at rest, I've no intention of bodging this at all - if anything else is required, insulation, plastering, ventilation etc. it shall be fitted
The comments about the planning permission, building warrant etc was only because I don't want to progress without these if they are required. Time to speak to the planning office and find out was what actually originally applied for I think.
The comments about the planning permission, building warrant etc was only because I don't want to progress without these if they are required. Time to speak to the planning office and find out was what actually originally applied for I think.
Matt
Can you confirm (by measuring) the span that the joists are covering, preferably in metres and centimetres
or even millimetres please. At the moment you seem to indicate about an 6m span, which is quite big, especially using 150x50s..
It will also depend on the grade of timber used.. It should be stamped on the joists somewhere, possibly
C16, C24, TR26 or similar..
A steel could be put in place, but as you've indicated, you'd then need to support the ends of the steel
adequately. To do this you'd need someone to work out the loads on the steel and also take into consideration
the span, for permissable deflection..
Can you confirm (by measuring) the span that the joists are covering, preferably in metres and centimetres
or even millimetres please. At the moment you seem to indicate about an 6m span, which is quite big, especially using 150x50s..
It will also depend on the grade of timber used.. It should be stamped on the joists somewhere, possibly
C16, C24, TR26 or similar..
A steel could be put in place, but as you've indicated, you'd then need to support the ends of the steel
adequately. To do this you'd need someone to work out the loads on the steel and also take into consideration
the span, for permissable deflection..
Busamav said:
So they are trusses .
Is the cross bracing at an angle .........or is there just one vertical member in the eaves each side .
If neither of the above , then 7x 2 floor joists on their own at that span are woefully inadequate for a domestic floor loading
Mine is 16 foot span, with 6" x 2" joists, on 24" centres, and it flexes as I crawl across it. Trusses were designed by a proper truss manufacturing company.Is the cross bracing at an angle .........or is there just one vertical member in the eaves each side .
If neither of the above , then 7x 2 floor joists on their own at that span are woefully inadequate for a domestic floor loading
It looks a bit misleading, but there is only 4 feet headroom in the centre.
OP could always add more joists alongside the originals? Twin them together.
For the flooring I used the ubiquitous chipboard loft flooring. Cheap and easy, and pretty strong.
Edited by King Herald on Monday 7th December 21:28
King Herald said:
Mine is 16 foot span, with 6" x 2" joists, on 24" centres, and it flexes as I crawl across it. Trusses were designed by a proper truss manufacturing company.
Typical commercial design. Timber will flex and feel uncomfortable well before maximum stress. IMHO 24"c/c is too much for a roof designed to take a floor but you can improve this all round by adding 2x2" as mentioned above.
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