Lowest profile flat roof ballasted system

[Mattg4321]

I've got a spare MPPT on my Sunsynk inverter.

 

I've got a garage (flat) roof on the side of my house I could fit 5 (or possibly 6, I've not bothered measuring yet!)  panels on, landscape to reduce height. It's south facing, with only moderate shading early/late in the year. Half the year it will be in full sun all day.

 

I'm sure it would payback within a couple of years or so as I can fit myself.

 

I don't want any penetrations through my flat roof and I don't want it to look awful. Are the ballasted systems any good? Roof structure is early 70's and in good condition. 4x2 timber. 2.4m span. Not sure if I will require structural engineer?

 

What's the lowest profile flat roof system? Do I require planning?

 

All input appreciated!

[TedM]

Hmmm. A quick look at good old AI suggests:

According to standard UK span tables (BS 5268), a 2" x 4" (specifically 47 x 100 mm) joist typically has a maximum allowable span of only 1.7 to 2.1 meters depending on the wood grade and spacing. At a 2.4m span, the joists are "undersized" and prone to significant sagging or structural failure under standard loads.

 

So maybe no planning required but some acro props probably will be as whatever you put up there may well try to find its way downstairs fairly quickly 😬

(The 70's has a lot to answer for!)

 

"I'm sure it would payback within a couple of years or so as I can fit myself."

 

Possibly a bit longer if you take roof repairs into account 😉

 

 

Edited 2 hours ago by TedM

[Mattg4321]

46 minutes ago, TedM said:

Hmmm. A quick look at good old AI suggests:

According to standard UK span tables (BS 5268), a 2" x 4" (specifically 47 x 100 mm) joist typically has a maximum allowable span of only 1.7 to 2.1 meters depending on the wood grade and spacing. At a 2.4m span, the joists are "undersized" and prone to significant sagging or structural failure under standard loads.

 

So maybe no planning required but some acro props probably will be as whatever you put up there may well try to find its way downstairs fairly quickly 😬

(The 70's has a lot to answer for!)

 

"I'm sure it would payback within a couple of years or so as I can fit myself."

 

Possibly a bit longer if you take roof repairs into account 😉

 

 

 

I think you're right. Will be giving this a miss then.

[BotusBuild]

FYI - It is not unheard of for sloping roof trusses needing to be strengthened when PV panels are fitted, so based on @TedM's findings I would be looking to add extra wood to the existing timbers.

A friendly SE's input would not go amiss in  this situation, especially as you are talking about ballast systems