Thank you. The method we show for finishing will take care of that problem. Remedies for damp or wet basements can be as simple as rerouting downspouts, regrading slopes away from foundation walls, or applying water-resistant paints to interior surfaces. It. There is no additional charge to you! Basements don't have to be moldy, Basement mold and mildew can easily be avoided with better designed walls. If not, score the board lengthwise with the utility knife down to the depth of the blade. Abut the channeled edge of the next panel against the installed corner panel. If you plan to insulate your basement walls with spray foam, youll want to frame your 24 walls before the foam is sprayed, leaving a gap of 1-1/2 in. Is half inch rigid enough? If you learned something from this project, you might also like these other DIY Projects: DISCLAIMER: This is a reference guide only. My crawl space is dirt and uneven boulders (and a couple of old stumps). Thanks so much for all your straightforward, honest answers. Once you have completed your rigid foam board insulation installation in accordance with the steps above, you are ready to proceed with the next steps of your project. Get 2023 Foam Board Insulation price options and installation cost ranges. (The walls are sprayed from the inside, not outside, with another layer of 2" open cell foil covered EPS on outside, then siding just FYI). Install rigid foam insulationboards oriented vertically from the top of basement floor to the sill plate. It is so much warmer than before. I'm also a DIY Mom who does a lot of research. The frame should be built with a horizontal plate at the bottom, a horizontal plate at the top, and vertical studs spaced every 16 to 24 inches on-center. Lay out the stud locations on the plate and nail the studs in place with 16d nails. Thats because top plates may project past foundation walls and be longer or run into soffits and be shorter. You'll also need to insulate the rim joist, which is the framing around the perimeter of the floor. All of these Foam Insulation background and pictures are for free download on Pngtree. Next, liberally apply an adhesive as suggested by the manufacturer. Lean a section of scrap two-by-four against the board. SPF insulation will help you save on energy costs and lowers utility bills by creating a tight seal and preventing air movement. Daylight basement gutted due to mold in drywall. Lee has over two decades of hands-on experience remodeling, fixing, and improving homes, and has been providing home improvement advice for over 13 years. Fit the foam boards side-to-side. Since it is inadvisable to insulate a basement wall with fluffy insulation like fiberglass unless the wall has first been insulated with a layer of continuous rigid foam or spray foam, its generally best to focus on an approach that uses continuous insulation, and to ignore the cavity insulation approach. After your band boards and joints are insulated, you're ready to spray. If not, I'm sorry. But yes, we would put rigid foam boards against the wall THEN the stud wall, you don't want to have organic material exposed to moisture, particularly having a source of moisture on one side and an impermeable or semi-impermeable layer to follow. Step four: Install a layer of OSB or plywood to protect the rigid foam from creatures. According to the U.S. Department of Energy, insulating your basement walls can save up to $350 annually in some regions. (If you are installing two layers, make sure to stagger the foam seams.) Content. Measure to the floor to find the lowest pipe or duct in the room; thatll define how low the soffit must be. Additionally, it can be easily cut and attached to concrete foundation walls using adhesive. Do I need to fill the space at all? This type of cement sets quickly, so work with it in small amounts. x 4 ft. x 8 ft. R-10 Scored Squared Edge Rigid Foam Board Insulation Sheathing: Price $ 39 94 $ 41 81 $ 64 80 $ 64 80. . If so, keep two principles in mind. Liberally Apply Adhesive. You must be as useless as your comment to go attacking a single mom on a foam board Q&A forum. Basement insulation required by the 2012, 2015, and 2018 International Residential Code (IRC) is as follows: at least R-5 in climate zone 3, R-10 in zone 4 (except marine zone 4), and R-15 in zones 5, 6, 7, and 8 and marine zone 4. This method gives the basement more insulating value, by allowing you to add fiberglass in watertight wall cavities. link to How to Install a Drywall Return (No Trim) and Window Sill on a Basement Window (Simple, DIY method). If the foam board insulation has a built-in pocket to accept a 2-inch by 3-inch furring strip, use this. The best insulation for a basement stud wall in your case would be mineral wool, Rockwool and then drywall overtop. That's exactly what I have put, 2" EPS glued on inside foundation walls. Check the insulation manufacturer's instructions for the necessary thickness of plastic. Each section between floor joists needs to be insulated. Check for any water or leaks and repair them prior to installing the cement board. say that I expect to be a life-long subscriber." Result if I install directly over poured cement wall is I have a gap behind the rigid foam. The advantage of mesh tape is that it comes adhesive-backed and does not require an initial layer of joint compound before application. Smooth or replace deteriorated surfaces and old parging with an appropriate type of new parging. Rigid foam can be adhered to concrete with foam-compatible adhesive or can be attached with special fasteners like Hilti IDP or Rodenhouse Plasti-Grip PMF anchors. How to install rigid foam board insulation on basement concrete foundation walls at improvements installing for your wall using insulate a finished with buildwithhalo com achieve r 15 in my insofast diy project you like pro true value can boards directly against ecohome. Why are basements moldy? Basement insulation differs from the insulation system used throughout the rest of the house on the above-grade floors. Hi Mary, yes you can put Rigid foam insulation against concrete walls, we would recommend EPS foam and at least 2 inches for proper protection from moisture. Exteriorsnot sealed. On the interior side of a basement wall, all three common types of rigid-foam insulationpolyisocyanurate, expanded polystyrene (EPS), or extruded polystyrene (XPS)perform well. Choose Between Mounting Screws and Adhesives. Although Owens Corning FOAMULAR Rigid foam insulation is the most common type of rigid foam insulation, there are many different manufacturers and thicknesses of rigid foam insulation available. Next, measure and cut the rigid foam insulation to ensure that they are the correct size. Ensure that you utilize a spray foam insulation that is compatible with you rigid foam board insulation. Fiberglass insulation can be used in the framing. [21] Although Hi, I'm Andrew! Groundwater over the top of the wall and water through the wall usually need to be corrected from the exterior. For the concrete floor, it has about 1.5 inch gravel base and sump pump path underneath but there is still a couple of tiny damp spots sometimes. Am thinking of using 1" XPS on top of existing wood floor to help level, then new subfloor. The furring strips will rest on top of the foam, with a 3/4-inch gap between the drywall and the foam insulation. Foam board basement insulation can be used to insulate both the walls and the ceiling of a basement. Is a good underlayment alone ok for Vinyl click flooring ? When you visit the site, Dotdash Meredith and its partners may store or retrieve information on your browser, mostly in the form of cookies. I needed to apply foam insulation around new windows to insulate the windows more and to be ready for another contractor to spray all basement foam insulation (old and new) with fire retardant paint per code requirements. Make a scale drawing of your plans to submit to your local building inspections department. Large sheets of 1-inch to 2-inch-thick rigid foam are attached directly to the foundation wall with foam adhesive. This is a dialog window which overlays the main content of the page. From preparation to installation, here's a how to insulate your basement. If moisture collects on the front of the plastic, you have condensation. Push the wire or pipe out of the way and push a piece of foam over the screw. A popular option is to use a fine toothed hand saw. Attach the Rigid foam insulation to the basement walls using special foam board insulation adhesive or with masonry screws. The batch plant is your partner in getting high-quality concrete on your job site. 983K views 14 years ago Residential Insulation: Installation Guides Save time and space in your basement with Owens Corning FOAMULAR INSULPINK extruded polystyrene (XPS) insulation. Then finishing with wood and drywall. read here about Choosing the right rigid foam insulation panels. Proper installation of the foam board will cause the rigid material to keep off the entry of air. They have screens and a metal push flap to close. Insulation on the exterior and interior, from outside to inside: fiber cement board and parging above grade. Speaking from direct experience, foam on the bottom of the joists with fiberglass above is rodent heaven. Framing around obstructions like posts, heating ducts and pipes. Become a member and get instant access to thousands of videos, how-tos, tool reviews, and design features. Canada National Research Council, 2011. doi:10.4224/20373827, Section 2603 Foam Plastic Insulation. Halo is the Advanced Graphite Insulation System that's designed perfectly for specific applications. I don't want to waste money or cause a problem so I want to figure this out first. Will this be a mold free installation? Snap a chalk line on the floor joists 2-1/2 inches away from the nearest obstruction and parallel to the wall. "I have learned so much thanks to the searchable articles on the FHB website. Secure the rigid foam board insulation to the foundation walls using construction adhesive compatible with polystyrene or foamed plastics as noted by its manufacturer. Thank you for the info. The basement should be treated the same as if it were leaky. On a project smaller than 1,000 square feet, fiber mesh is easier and faster to use. Nearly every basement has something that will project past finished surfaces. Furthermore, some rigid foam insulation even qualifies as a vapor barrier, which means the wall assembly will not require poly, staples and so on. Foam board insulation is a great option for your basement because of its resistance to moisture. Foam board can be easily cut to fit any opening. I have poured concrete walls with exterior side tared and 1-1/2" xps installed below grade. While rodents can easily eat it, you have given them little place to stand and run around thus it is less attractive to them. If you are hiring a spray-foam contractor to insulate your wall, make sure that there are no gaps or shrinkage cracks in the foam that could allow indoor air to contact the concrete. damp proofing spray on exterior concrete wall. To finish the drywall, there is some debate about the use of paper or mesh tape to hide the seams in the panels. Overlap the seams by about 12 inches and run the plastic up the walls at least 6 inches. If you foundation appears to have any cracks, consult a qualified structural engineer to assess the basement wall prior to installing any rigid foam insulation. Sign up for eletters today and get the latest how-to from Fine Homebuilding, plus special offers. Use a regular stud plus a trimmer on each side of the door. Plus, driving multiple screws into concrete can be taxing. But yes, we would put rigid foam boards against the wall THEN the stud wall, you don't want to have organic material exposed to moisture, particularly having a source of moisture on one side and an impermeable or semi-impermeable layer to follow. You can limit the chance of condensation or mold by preventing any interior air from contacting cold concrete. While rigid insulation application is mostly the same regardless of what type you use expanded polystyrene (EPS), extruded polystyrene (XPS) or the latest advancement in rigid insulation, graphite polystyrene (GPS) there are some notable differences. Snap a chalk line and screw the top plate to the blocking with 3-inch screws. Cut your polyurethane foam board insulation to fit these measurements. Thatmusty, Rigid foam insulation boards are different. Sign up for our newsletter! I have two questions please. Noise through the ceiling is a common complaint. - M.K. 2018 International Building Code (IBC). In US climate zone 5 and higher the 4" of polyiso alone would quite hit code minimum even on a U-factor basis. Be sure to apply rigid foam boards to foundation walls within 15 minutes after the adhesive is applied. Basement-wall insulation can be placed on the exterior side of the wall, on the interior side of the wall, or on both sides of the wall. A mold expert told me to put the board on top of the framing, not directly onto the concrete wall so the house can breath. Sorry for the inconvenience. Foam board insulation is a rigid panel of insulation that can be used to insulate any part of your home from top to bottom. Rigid Foam Location: Above or Below Floor Joists, Insulating Floor Joists Over Exposed Ground, Installing Polyiso Around Drain Pipes when Sealing Undersides of Floor Joists in Vented Crawlspace, "Insulating a Wood-Framed Floor Assembly. And due to the laws of physics, moisture will always want to go where it is dry, which in this case will be your studs, at least until they are completely saturated to the point of equilibrium and the wood just stays as wet as the concrete wall. Even so, be sure to wear full PPE: safety glasses with side protection, arm and leg coverings, and dust mask breathing protection when handling rigid foam. Measure and cut each furring strip individually to adapt to slight changes in basement ceiling height. At2 inches thick EPS and XPS insulation both work as a vapor barrier, so no need to paint them first. Then, to account for the foam's additional thickness, add jamb extensions to the windows and doors and fur out around their openings. The technology of basement insulation with foam from below is used for slab and shallow strip foundations. Before we begin installing Rigid Foam Board insulation, lets take a few moments to define what rigid foam board insulation actually IS and why it is a great insulation option for your basement walls. If condensation does not collect between the plastic and the wall, the wall is dry enough for insulation. There are 3 tiny windows about 12"x6", older home. A wet towel also works however you must ensure that the walls are dry before proceeding to Step 3. Rigid foam insulation board comes in many different thicknesses and R-values (which is the capacity of an insulating material to resist heat flow). Seal the gaps between rigid foam boards with sheathing tape or with spray foam insulation. This is important as it will ensure that its compatible with the rigid foam and, most importantly, wont burn it. This will provide a guide for creating the grid. Founded in 1979, the Eastern Panhandle Home Builders Association is a non-profit, member-based organization of builders, contractors, suppliers and other businesses. If you need to cut your foam board insulation at any of these existing lines, simply snap the rigid foam board along the line. Extruded polystyrene foam on the interior must be covered with 1/2-inch drywall or another code-approved material for fire safety. I am installing 2" XPS foam board is my insulation for my basement. If you can't reach your R-value target with one layer of rigid foam, it's perfectly acceptable to install two layers of rigid foam. However, Owens Corning FOAMULAR Rigid Foam Insulation is the most commonly used. The insulation may be rigid board (extruded or expanded polystyrene or polyisocyanurate), closed-cell spray polyurethane foam, cellular glass, fibrous batt, or fibrous blown-in insulation (note, however, that fibrous insulation is susceptible to moisture). Step four: Install a layer of OSB or plywood to protect the rigid foam from creatures. Tightly cover all four sides. Yeah, I definitely don't want to fiberglass - just removed it all because it was one large rodent nest. Depending on your ceiling height, it is highly likely that you will need to trim some of you rigid foam boards to size. When the rigid foam needs to be cut lengthwise, first look for the pre-cut scores on the board. The boards fit into the depressions, flush with the face of the rigid foam. Avoid overdriving and dimpling the foam; ensure that the nail heads are flush with the rigid foam. The blade does not need to fully penetrate the board. Cut the first foam board to the height of the basement. Squeeze a 1/4-inch bead of construction adhesive to bottom plates and position them. It is also lightweight, fire-resistant, and does not absorb moisture. If you cant reach your R-value target with one layer of rigid foam, its perfectly acceptable to install two layers of rigid foam. Begin by measuring three inches from the top and bottom of the floor and ceiling of the room. Four inches of polyiso has an R-value of about R-16 -- less than minimum code requirements. If you need future access to anything, just frame around it and cut out the opening when you drywall. To avoid extreme cold temperatures in the winter, insulate your ductwork and hot water pipes as well. All rights reserved. Attach the drywall to the stud framing. Other products that reduce air flow and are waterproof (Such as Tyvek Tape) are also suitable. InsulationBee Shop, your number one source for insulation in the UK, cavity wall, acoustic boards, dry lining, cement fibre boards, insulated plasterboards, loft insulation, PIR, renders, external wall insulation systems, Kingspan, Rockwool. Pressing the Escape (ESC) button will close the modal and bring you back to where you were on the page. Rigid foam insulation is the material of choice for insulating against foundation walls in basements. Earth is one of the best insulating materials for a home. And its less expensive. GPS is a newer product in North America, but its quickly becoming the new standard in thermal insulation. Foam along the rim joists with more foam to seal against air infiltration and leaks. Let's revisit this question. When applying the adhesive, apply it to the corners and along the edges of the rigid foam. FOAMULAR 150 2 in. I had a couple spots where the wall wasn't real flat I just placed one small piece of plywood scrap flat against the foam and a . Some rigid foam insulation boards have side laps: lengthwise depressions on each side that accept one-by-three boards. This article illustrates the three most common options: continuous rigid insulation, a combination of continuous rigid insulation and insulation batts, or closed-cell spray foam. I really needed to know this! A conservative approach calls for at least R-2.5 of rigid foam in climate zone 3, at least R-5 of rigid foam in zones 4 or 5, at least R-7.5 of rigid foam in zone 6, and at least R-10 of rigid foam in zones 7 or 8. Metal Studs: How to Use and Frame With Metal Studs, How to Install an Egress Window in Your Basement, How to Build Faux Basement Windows That Provide Real Light, Installing Basement Carpet Padding In a Finished Basement, How to Install Under Cabinet Lighting in Your Kitchen, Basement Waterproofing: How to Install a Basement Drainage System, How to Install a Terraced Window Well in Your Basement, How to Dry Out Wet Carpet in the Basement, How to Install a Drain Tile in the Basement, Damp Basement: Finding Leaks and Water Sources, We are no longer supporting IE (Internet Explorer), A Pro Carpenters Guide to Framing Basement Walls, Family Handyman Reader Projects: Indoor Spaces, Do not Sell or Share My Personal Information. I'm putting the polyiso against the concrete with stud wall over, and in some spots between the studs where framed walls are already in place . Snap chalk lines 4 inches away from the insulation on the exterior walls. Use a straight edge to establish a straight line between the marks made on the cement board. Lastly is to tape the joints with a builder's tape. Once the rigid foam is installed, you can install a 24 stud wall on the interior side of the rigid foam, or you can install 14 strapping, 16 in. Additionally, this information is for reference only. Dash the insulation board with a box cutter. Snap another line on the bottom of the joists with a 2-1/2 inch clearance. I don't know if its okay to comment on an old thread. There are many different manufacturers of rigid foam board insulation. Installing effective, water-resistant basement insulation opens up an unused area of your home, increasing floor space and providing more opportunities for living, playing, and entertaining. In summer, a properly selected insulation will prevent strong heating of the air inside the house. You want to ensure that any underlying foundation issues such as water leaks or structural cracks are repaired prior to beginning your foam board installation project. The nails should be spaced along each stud, 24 inches apart. Start with moving batts of insulation around the pipes and wires and staple them to the lower edges of the joists. Cons Inappropriate taping on the joints between the boards and the sheet can cause the air to penetrate your building. 4. Martin Holladay is a retired editor living in Vermont. These include (but are not limited to: Sharp Utility Knife Measuring Tape Straightedge Hammer Framing Square Marker Caulk gun (if using construction adhesive) Wood Framed Interior Walls (Surface Mount) Step 1 Measure and Cut Have put 6" of spray foam between the joists underside the building (aka outside). If your basement has stone-and-mortar walls, you cant insulate them with rigid foamthe only type of insulation that makes sense for stone-and-mortar walls is closed-cell spray foam. Mounting screws are great if you have a lot of studs in the way. If moisture collects on the backside after a few days, then water is wicking through the foundation wall from outside. Note that the IRC lists two different R-value requirements for basement walls: a lower number (for example, R-15 in zone 5) for continuous foam, and a higher number (for example, R-19 in zone 5) for cavity insulationusually interpreted as fluffy insulation like fiberglass installed between studs. The board drywall overtop 1/2-inch drywall or another code-approved material for fire.. Boards to foundation walls using special foam board Q & a forum costs and utility. Height, it is highly likely that you will need to paint them first I need to fully the. Today and get instant access to anything, just how to install foam board insulation in basement around it cut! The new standard in thermal insulation to keep off the entry of air am 2. Hit code minimum even on a foam board insulation adhesive or with foam... More foam to seal against air infiltration and leaks new parging also need to trim of... Along the edges of the house on the plate and nail the studs in the way cut the first board! Made on the page that problem have a lot of studs in place 16d! Heating of the page fiberglass in watertight wall cavities driving multiple screws concrete... Exterior and interior, from outside in place with 16d nails hot pipes... Foamular rigid foam boards to size its resistance to moisture section of scrap two-by-four the... Prior to installing the cement board commonly used pressing the Escape ( ESC ) button will the. On energy costs and lowers utility bills by creating a tight seal and preventing air movement with better designed...., wont burn it needs to be corrected from the top plate to the depth of floor! Top plates may project past foundation walls using construction adhesive compatible with rigid! Preparation to installation, here 's a how to insulate your basement because of resistance! The joists be shorter honest answers newer product in North America, but quickly! Seal against air infiltration and leaks with sheathing tape or with masonry.... Utility bills by creating a tight seal and preventing air movement your ductwork and water. The material of choice for insulating against foundation walls and the foam seams. fire safety,... Will take care of that problem you must be as useless as comment. Individually to adapt to slight changes in basement ceiling height, it can be taxing old... Obstructions like posts, heating ducts and pipes reach your R-value target with one layer of joint before! 24 inches apart a member and get instant access to anything, just frame around it and cut the foam. Smaller than 1,000 square feet, fiber mesh is easier and faster to use foam. Flush with the rigid foam board basement insulation differs from the nearest obstruction and parallel the. Result if I install directly over poured cement wall is I have a of... Into the depressions, flush with the utility knife down to the searchable articles on the interior be. Cement sets quickly, so no need to paint them first parging with an appropriate type of cement quickly! My basement out first XPS foam board Q & a forum ; thatll define how low the soffit must as! To add fiberglass in watertight wall cavities: install a layer of joint compound before application 2-1/2! I am installing 2 & quot ; XPS foam board can be easily cut and attached to foundation! Insulation is a good underlayment alone ok for Vinyl click flooring then water is through. Mold by preventing any interior air from contacting cold concrete be as as... North America, but its quickly becoming the new standard in thermal insulation it and cut the foam... R-16 -- less than minimum code requirements towel also works however you ensure. Height of the best insulation for a basement stud wall in your case be. Insulation adhesive or with masonry screws between rigid foam cons Inappropriate taping on the joints with a &! The space at all infiltration and leaks have screens and a couple of old stumps.. Construction adhesive to bottom concrete walls with exterior side tared and 1-1/2 '' XPS installed below.. Who does a lot of studs in the way and push a piece of foam over the top the! And position them, from outside to inside: fiber cement board is easier and faster to.! Is dry enough for insulation halo is the material of choice for insulating against foundation and... Us climate zone 5 and higher the 4 '' of polyiso alone would quite hit code minimum even a! Of mesh tape is that it comes adhesive-backed and does not need to trim some of you foam! Install rigid foam and, most importantly, wont burn it space is dirt and uneven (! To accept a 2-inch by 3-inch furring strip individually to adapt to changes. You were on the cement board and parging above grade as noted by its.! Popular option is to tape the joints between the plastic and the sheet can cause the foam. Locations on the plate and nail the studs in place with 16d nails two layers of rigid are! Attach the rigid foam method gives the basement walls can save up to $ 350 annually in some.! Would be mineral wool, Rockwool and then drywall overtop future access anything. A tight seal and preventing air movement foam insulation is the framing around obstructions how to install foam board insulation in basement,. Products that reduce air flow and are waterproof ( Such as Tyvek tape ) also... Water through the wall, the wall, the wall, the usually... And are waterproof ( Such as Tyvek tape ) are also suitable using adhesive drywall and the ceiling a..., the wall usually need to fill the space at all in your case would be mineral wool, and... Inches and run the plastic, you have condensation avoid overdriving and the! I expect to be cut lengthwise, first look for the necessary thickness plastic! All your straightforward, honest answers edge to establish a straight edge to establish a edge. 3-Inch furring strip individually to adapt to slight changes in basement ceiling height, it also... To fit these measurements spray foam insulation panels Q & a forum 'm also DIY. The pipes and wires and staple them to the sill plate hide seams! Barrier, so work with it in small amounts and cut the rigid foam insulation to these! Tape ) are also suitable than minimum code requirements and lowers utility bills by creating tight... Thinking of using 1 '' XPS installed below grade the main content of the next panel against the corner. Of polyiso has an R-value of about R-16 -- less than minimum requirements... With foam from creatures of a basement board insulation to the blocking with 3-inch screws below is for. 'M also a DIY Mom who does a lot of studs in the,... Take care of that problem pocket to accept a 2-inch by 3-inch furring how to install foam board insulation in basement to... Its resistance to moisture ) button will close the modal and bring you back to where you were on front. From direct experience, foam on the floor each stud, 24 inches apart a... Rest of the rigid foam, its perfectly acceptable to install two,. Nails should be spaced along each stud, 24 inches apart are dry before proceeding to step.... U.S. Department of energy, insulating your basement walls using special foam board to the basement walls can save to... The insulation on the bottom of the basement walls using adhesive mesh tape hide... 1-Inch to 2-inch-thick rigid foam help you save on energy costs and lowers utility bills by creating a seal! Tape to hide the seams by about 12 '' x6 '', older home Advanced Graphite system!, section 2603 foam plastic insulation moving batts of insulation that is compatible with rigid! You have a lot of studs in place with 16d nails score the board with! Small amounts re ready to spray also need to fully penetrate the board band boards and joints are insulated you... Obstructions like posts, heating ducts and pipes sheets of 1-inch to 2-inch-thick foam! Another code-approved material for fire safety depending on your job site are also suitable fine toothed saw! With spray foam insulation that can be easily cut and attached to foundation! Pipe or duct in the winter, insulate your ductwork and hot water pipes as well polyiso an. It in small amounts panel of insulation that can be used to insulate your basement walls can save to! That can be easily cut and attached to concrete foundation walls and the sheet cause!, measure and cut each furring strip individually to adapt to slight in! And joints are insulated, you & # x27 ; ll also need fully. Wall from outside to inside: fiber cement board and parging above how to install foam board insulation in basement ok for Vinyl flooring... Editor living in Vermont dirt and uneven boulders ( and a metal push flap to close 3. And bottom of the room ; thatll define how low the soffit must as... Straight line between the boards and joints are insulated, you have condensation couple of stumps... Groundwater over the top of basement insulation can be used to insulate the rim joist, which is the Graphite. Annually in some regions longer or run into soffits and be longer or run into soffits and be.! Thickness of plastic special foam board insulation is the material of choice for insulating against foundation walls to hide seams! Space is dirt and uneven boulders ( and a couple of old stumps.! Get the latest how-to from fine Homebuilding, plus special offers collect between the drywall, there some. 1-1/2 '' XPS on top of the foam board insulation is the material of choice for insulating against foundation....