gap around new windows

getfit

The windows for my build were installed yesterday. Very happy with them and everything seems fine. As is the norm there are small gaps between the window and wall in certain spots.

I intend getting a good few expandable foam cans and sealing around the gaps so that the window is kept fairly air tight.

Is this a good plan??? Is there a better product than expandable foam for this?? My original plan was to use silicone, but now that the windows are in I can see that some gaps are far to big for silicone.

topcatcbr

why are the gaps too big for silicone. is the external wall brick, stone or plastered block. Be carefull with foam as it expands quite alot and can make a bad mess as it sticks to everything and can be impossible to remove.

De_man

good time to get the windows in:)

i'm assuming all the openings around the windows were blocked up with insulation before the windows were installed...otherwise the foam could go
all over the place in the cavity

if so,,
i used expanding foam in my place, be very careful not to overdo the
spray otherwise it'll go everywhere !!!!

i found (in my limited experience) to reduce the amount of expansion of the
foam,, to lightly spray the expanding foam with water once it begins to expand...(use a clean detergent bottle) it is possible to get foam that has very limited expansion, but i'd say you'll have a job in finding it

once it goes hard, using a paint scrapper (with insulation tape on end)
push the foam from the sides of the window back into cavity, removing any excess with a sharp knife

if you've got spare insulation around the place you could also use this
by pushing it into the gap and trim off...save you a good few quid

very slow job to do it properly

De_man

topcatcbr wrote: »

can make a bad mess as it sticks to everything and can be impossible to remove.

i agree with that...;) when doing the top part of the windows you'll find
it expanding and dropping down most likely on to the glass and the window frames....don't panic and don't attempt to remove it at this stage....
you'll be wasting your time

wait until it drys and lightly scrap off....just be very careful with the
amount of foam applied

bakerbhoy

Get an applicator gun.Much more controlable and less waste.Cans are different for applicator gun.
Gun is around €20 well worth it.

RKQ

I agree with above. Use masking tap to protect frames!
(Got some foam on my thumbnail 3 months ago - still not completely gone!)
Its very sticky stuff.

You might consider buying Airtight tape, its about 50mm wide. There are a number of brands available.
Its very sticky and ideal to tape frame to head (top) and reveals (sides). Easily sticks to blockwork / plastic, plaster, wood etc.
Perfect airtight seal.

sinnerboy

I agree with RKQ and the others - only more so

The PU foam is good for gap sealing but the tape is essential to ensure long term air tightness

Siga , Vario and Intello are the different systems to look at - ( the tape being only a small part of each system )

ircoha

As well as helping with airtightness, the tape will help to reduce the passage of sound through the foam.

I dont really like the foam as it is, unlike myself, not dense enough:) for sound reduction. However this is a personal opinion.

The other point is that if u use too much foam and the windows are open when doing it the frame may bulge and the window wont close.

The applicator gun is essential, as well as moistening the windows space before u apply a small amount.
If u use masking or other tape to protect the frame, which I think u should, remove it ASAP

De_man

typical, i found the hard way to do it....put in the foam trimmed back, then taped up.... if only i had known about a specific applicator gun:rolleyes:

wud have saved me a fortune in foam cost and my sanity

must keep an eye out for that applicator gun

Slig

You should also take into consideration that the foam only lasts about 2 years. technically the gaps should be filled by plastering on inside and rendering on outside by then

Builderfromhell

I believe some expanding foams are designed for use around windows. They do not put too much pressure on frame while expanding. can't think of the name.

gman2k

Hilti do a foam called air sealer, specifically designed for the job. Very expensive though (c. €400 for 12 cans), and you need the Hilti foam applicator gun also (another €80).
The benefits are;
Slow release foam - will not buckle windows or doors, not like the cheap and nasty alternatives.
Forms an airtight seal, not like the cheap and nasty alternatives...
Forms a flexible seal, not like...... you get the message!

http://www.hilti.ie/holie/modules/prcat/prca_navigation.jsp?OID=-26240

But as the guys above said, use an airtight tape around opes also. I've used siga tapes and found them great.
http://www.siga.ie/e_index.htm

All the above may sound like big money, but the devil is in the detail, and this is where a lot of energy is lost very easily....