Sub-floor ventilations - How to decide on the companies

[Angry_eel]

O.P.
this post was edited
Hi,

I got 2 quotes from a couple of companies for sub floor ventilation. I have dampness on the high side of the house(on the side of a hill) which increases after a heavy rain. I am unsure which one to decide on as I've never had these things done before.

- Guy 1 came around looked all under the house, drew a plan and gave me a quote for $2200 for 1 fan, removing bricks in a wall and around 30 metres of ducting. The cost might be reduced to $2k but that was if I did it pre financial year end.
- Guy 2 came around and took a quick look near the edge of the entry and a few other openings, gave me a quote for $2000 for 2 fans, ducting and no brick removal(will use open area for the air). He will put the whole thing in the problem area. He said the air will flow in the entire sub-floor as there were openings in other areas.

From the cost of the parts alone, the second guy is putting more in. However, He never even had a look under the house which concerns me. In his opinion, they do this every week and certainly from his ute, it looked like he had plenty of work.

I have never had one of these done before. Help needed.

 

[Twizzle]

With sub floor ventilation, it only has to be equal to 5% of your floor area to comply with part F of the National Construction Code, no fans required. Vents are to be installed diagonally opposite to one another, you must have flow through, all the openings in one wall will not achieve much.

I generally find that when people ask for details on sub floor ventilation to rid the place of mould and rising damp, the problem is not ventilation, or lack there of, its water infiltration. You need to find where the water is entering and if its on the high side, as you say, you should have a drainage pit to stop the water ponding on the high side of the residence and hence it infiltrating to the sub floor area. If you cant facilitate a gully pit then try some sort of open drain to let the water drain away.

 

[Angry_eel]

With sub floor ventilation, it only has to be equal to 5% of your floor area to comply with part F of the National Construction Code, no fans required. Vents are to be installed diagonally opposite to one another, you must have flow through, all the openings in one wall will not achieve much.

I generally find that when people ask for details on sub floor ventilation to rid the place of mould and rising damp, the problem is not ventilation, or lack there of, its water infiltration. You need to find where the water is entering and if its on the high side, as you say, you should have a drainage pit to stop the water ponding on the high side of the residence and hence it infiltrating to the sub floor area. If you cant facilitate a gully pit then try some sort of open drain to let the water drain away.

Ah Twizz! Someone who knows what my problem is. Yes, you are right, there is a problem on the high side of the house. However, someone has put in a concrete floor and a retaining wall next to the house over the years. I'll take a pic and post it in here. I need to find out what sort of trade will look at fixing this issue so I am not wasting my money.

 

[Twizzle]

Its an engineer's job to design and control storm water drainage but it may be very simple.

Pics could help.

 

[Angry_eel]

Here you go:

https://drive.google.com/open?id=1Y8WkH3gZB4CwkkXG9YbXt_ShEdu2yy18 - Pic 1

https://drive.google.com/open?id=148ULG15qnQSKFiciOzLveW2glwh5KX3S - Pic 2

https://drive.google.com/open?id=1R3CiqFLDSCKjDfuywnkOlmx3WWqRgr5m- Pic 3

The dampness problem is all along this wall. In Pic 1, You can see the retaining wall and the soil has gone down over the time we've been here(1 year). Pic 3 shows the cuts in the concrete which may also be seeping water in. You can see the colour of the concrete which shows where the rain falls.

What kind of engineer do I need? Once the engineers plan is done, what trade then fixes this sort of thing? As a ballpark figure, what sort of costs am I looking at?

 

[Twizzle]

You have to work out how the water is getting under the house so sealing the path to the house will help. The path does not have any fall so hard to drain the path.

What should have happened is the path should fall away from the house, and that can be re-done and probabaly the best idea. If you get mould in the house you are screwed and will cost a fortune to rid it. Then have a spoon drain or aggy drain between the path and garden bed.

Ideally if you re-lay the path you would have gully pits in the path with fall to the pits so water can drain away, the plumbing would be laid prior to laying the new path.

If you dont act on this and you get mould which can take years, you will need to strip the plaster from your house, kill all the mould then re-plaster and paint, very expensive.

 

[Angry_eel]

You have to work out how the water is getting under the house so sealing the path to the house will help. The path does not have any fall so hard to drain the path.

What should have happened is the path should fall away from the house, and that can be re-done and probabaly the best idea. If you get mould in the house you are screwed and will cost a fortune to rid it. Then have a spoon drain or aggy drain between the path and garden bed.

Ideally if you re-lay the path you would have gully pits in the path with fall to the pits so water can drain away, the plumbing would be laid prior to laying the new path.

If you dont act on this and you get mould which can take years, you will need to strip the plaster from your house, kill all the mould then re-plaster and paint, very expensive.

Thanks so much for all this. Now, don't mind my newbie questions. I work in tech and building/plumbing/landscaping is not my forte. Like I said, I want to act on it but I don't know who to approach to start the job.

What would you recommend I start with?

Relaying the path - Does that mean breaking up the concrete and relaying the path with plumbing? Again, how do I start with this?

 

[Twizzle]

Relaying the path - Does that mean breaking up the concrete and relaying the path with plumbing? Again, how do I start with this?

yep, break it all up, remove it and start again

sometimes you can have pits without the drainage, just a big hole full of gravel and it disburses but in this case it will retain the water at the high side of your house, so you really need to drain the water away, so yeah, a plumber then a concreter if you dont have any mates who are in the trade or can help you out.

one possible cheap way out maybe to cut the conc path and lay the draining then seal it bck up but looking at you conc path, it may fall to bits so I dont think you can re-use it

 

[Angry_eel]

yep, break it all up, remove it and start again

sometimes you can have pits without the drainage, just a big hole full of gravel and it disburses but in this case it will retain the water at the high side of your house, so you really need to drain the water away, so yeah, a plumber then a concreter if you dont have any mates who are in the trade or can help you out.

one possible cheap way out maybe to cut the conc path and lay the draining then seal it bck up but looking at you conc path, it may fall to bits so I dont think you can re-use it

Alright, so contact a plumber for the job, break the concrete(myself or hire someone), plumber lays the pipes, book a concreter to pour the concrete in.

What about Engineer, still need them?

Will landscapers help, in terms of giving it a better look than it currently has but also solving the problem?

 

[Twizzle]

Alright, so contact a plumber for the job, break the concrete(myself or hire someone), plumber lays the pipes, book a concreter to pour the concrete in.

What about Engineer, still need them?

Will landscapers help, in terms of giving it a better look than it currently has but also solving the problem?

You just got engineering for free and I wouldn't worry about horticulturists in this case.

If I were you I would get the plumber and concreter out first before you break it up as they might come up with a better idea. I've only looked at 2 pics.

 

[Angry_eel]

Thanks Twizz. I have contacted a few plumbers.